START-INFO-DIR-ENTRY * Text utilities: (textutils). GNU text utilities. * cat: (textutils)cat invocation. Concatenate and write files. * cksum: (textutils)cksum invocation. Print POSIX CRC checksum. * comm: (textutils)comm invocation. Compare sorted files by line. * csplit: (textutils)csplit invocation. Split by context. * cut: (textutils)cut invocation. Print selected parts of lines. * expand: (textutils)expand invocation. Convert tabs to spaces. * fmt: (textutils)fmt invocation. Reformat paragraph text. * fold: (textutils)fold invocation. Wrap long input lines. * head: (textutils)head invocation. Output the first part of files. * join: (textutils)join invocation. Join lines on a common field. * md5sum: (textutils)md5sum invocation. Print or check message-digests. * nl: (textutils)nl invocation. Number lines and write files. * od: (textutils)od invocation. Dump files in octal, etc. * paste: (textutils)paste invocation. Merge lines of files. * pr: (textutils)pr invocation. Paginate or columnate files. * ptx: (textutils)ptx invocation. Produce permuted indexes. * sort: (textutils)sort invocation. Sort text files. * split: (textutils)split invocation. Split into fixed-size pieces. * sum: (textutils)sum invocation. Print traditional checksum. * tac: (textutils)tac invocation. Reverse files. * tail: (textutils)tail invocation. Output the last part of files. * tsort: (textutils)tsort invocation. Topological sort. * tr: (textutils)tr invocation. Translate characters. * unexpand: (textutils)unexpand invocation. Convert spaces to tabs. * uniq: (textutils)uniq invocation. Uniquify files. * wc: (textutils)wc invocation. Byte, word, and line counts. END-INFO-DIR-ENTRY This file documents the GNU text utilities. Copyright (C) 1994, 95, 96 Free Software Foundation, Inc. Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the Foundation. GNU text utilities ****************** This manual documents version 2.0 of the GNU text utilities. Introduction ************ This manual is incomplete: No attempt is made to explain basic concepts in a way suitable for novices. Thus, if you are interested, please get involved in improving this manual. The entire GNU community will benefit. The GNU text utilities are mostly compatible with the POSIX.2 standard. Please report bugs to . Remember to include the version number, machine architecture, input files, and any other information needed to reproduce the bug: your input, what you expected, what you got, and why it is wrong. Diffs are welcome, but please include a description of the problem as well, since this is sometimes difficult to infer. *Note Bugs: (gcc)Bugs. This manual was originally derived from the Unix man pages in the distribution, which were written by David MacKenzie and updated by Jim Meyering. What you are reading now is the authoritative documentation for these utilities; the man pages are no longer being maintained. The original `fmt' man page was written by Ross Paterson. Franc,ois Pinard did the initial conversion to Texinfo format. Karl Berry did the indexing, some reorganization, and editing of the results. Richard Stallman contributed his usual invaluable insights to the overall process. Common options ************** Certain options are available in all these programs. Rather than writing identical descriptions for each of the programs, they are described here. (In fact, every GNU program accepts (or should accept) these options.) A few of these programs take arbitrary strings as arguments. In those cases, `--help' and `--version' are taken as these options only if there is one and exactly one command line argument. `--help' Print a usage message listing all available options, then exit successfully. `--version' Print the version number, then exit successfully. Output of entire files ********************** These commands read and write entire files, possibly transforming them in some way. `cat': Concatenate and write files ================================== `cat' copies each FILE (`-' means standard input), or standard input if none are given, to standard output. Synopsis: cat [OPTION] [FILE]... The program accepts the following options. Also see *Note Common options::. `-A' `--show-all' Equivalent to `-vET'. `-B' `--binary' On MS-DOS and MS-Windows only, read and write the files in binary mode. By default, `cat' on MS-DOS/MS-Windows uses binary mode only when standard output is redirected to a file or a pipe; this option overrides that. Binary file I/O is used so that the files retain their format (Unix text as opposed to DOS text and binary), because `cat' is frequently used as a file-copying program. Some options (see below) cause `cat' read and write files in text mode because then the original file contents aren't important (e.g., when lines are numbered by `cat', or when line endings should be marked). This is so these options work as DOS/Windows users would expect; for example, DOS-style text files have their lines end with the CR-LF pair of characters which won't be processed as an empty line by `-b' unless the file is read in text mode. `-b' `--number-nonblank' Number all nonblank output lines, starting with 1. On MS-DOS and MS-Windows, this option causes `cat' to read and write files in text mode. `-e' Equivalent to `-vE'. `-E' `--show-ends' Display a `$' after the end of each line. On MS-DOS and MS-Windows, this option causes `cat' to read and write files in text mode. `-n' `--number' Number all output lines, starting with 1. On MS-DOS and MS-Windows, this option causes `cat' to read and write files in text mode. `-s' `--squeeze-blank' Replace multiple adjacent blank lines with a single blank line. On MS-DOS and MS-Windows, this option causes `cat' to read and write files in text mode. `-t' Equivalent to `-vT'. `-T' `--show-tabs' Display TAB characters as `^I'. `-u' Ignored; for Unix compatibility. `-v' `--show-nonprinting' Display control characters except for LFD and TAB using `^' notation and precede characters that have the high bit set with `M-'. On MS-DOS and MS-Windows, this option causes `cat' to read files and standard input in DOS binary mode, so the CR characters at the end of each line are also visible. `tac': Concatenate and write files in reverse ============================================= `tac' copies each FILE (`-' means standard input), or standard input if none are given, to standard output, reversing the records (lines by default) in each separately. Synopsis: tac [OPTION]... [FILE]... "Records" are separated by instances of a string (newline by default). By default, this separator string is attached to the end of the record that it follows in the file. The program accepts the following options. Also see *Note Common options::. `-b' `--before' The separator is attached to the beginning of the record that it precedes in the file. `-r' `--regex' Treat the separator string as a regular expression. Users of `tac' on MS-DOS/MS-Windows should note that, since `tac' reads files in binary mode, each line of a text file might end with a CR/LF pair instead of the Unix-style LF. `-s SEPARATOR' `--separator=SEPARATOR' Use SEPARATOR as the record separator, instead of newline. `nl': Number lines and write files ================================== `nl' writes each FILE (`-' means standard input), or standard input if none are given, to standard output, with line numbers added to some or all of the lines. Synopsis: nl [OPTION]... [FILE]... `nl' decomposes its input into (logical) pages; by default, the line number is reset to 1 at the top of each logical page. `nl' treats all of the input files as a single document; it does not reset line numbers or logical pages between files. A logical page consists of three sections: header, body, and footer. Any of the sections can be empty. Each can be numbered in a different style from the others. The beginnings of the sections of logical pages are indicated in the input file by a line containing exactly one of these delimiter strings: `\:\:\:' start of header; `\:\:' start of body; `\:' start of footer. The two characters from which these strings are made can be changed from `\' and `:' via options (see below), but the pattern and length of each string cannot be changed. A section delimiter is replaced by an empty line on output. Any text that comes before the first section delimiter string in the input file is considered to be part of a body section, so `nl' treats a file that contains no section delimiters as a single body section. The program accepts the following options. Also see *Note Common options::. `-b STYLE' `--body-numbering=STYLE' Select the numbering style for lines in the body section of each logical page. When a line is not numbered, the current line number is not incremented, but the line number separator character is still prepended to the line. The styles are: `a' number all lines, `t' number only nonempty lines (default for body), `n' do not number lines (default for header and footer), `pREGEXP' number only lines that contain a match for REGEXP. `-d CD' `--section-delimiter=CD' Set the section delimiter characters to CD; default is `\:'. If only C is given, the second remains `:'. (Remember to protect `\' or other metacharacters from shell expansion with quotes or extra backslashes.) `-f STYLE' `--footer-numbering=STYLE' Analogous to `--body-numbering'. `-h STYLE' `--header-numbering=STYLE' Analogous to `--body-numbering'. `-i NUMBER' `--page-increment=NUMBER' Increment line numbers by NUMBER (default 1). `-l NUMBER' `--join-blank-lines=NUMBER' Consider NUMBER (default 1) consecutive empty lines to be one logical line for numbering, and only number the last one. Where fewer than NUMBER consecutive empty lines occur, do not number them. An empty line is one that contains no characters, not even spaces or tabs. `-n FORMAT' `--number-format=FORMAT' Select the line numbering format (default is `rn'): `ln' left justified, no leading zeros; `rn' right justified, no leading zeros; `rz' right justified, leading zeros. `-p' `--no-renumber' Do not reset the line number at the start of a logical page. `-s STRING' `--number-separator=STRING' Separate the line number from the text line in the output with STRING (default is the TAB character). `-v NUMBER' `--starting-line-number=NUMBER' Set the initial line number on each logical page to NUMBER (default 1). `-w NUMBER' `--number-width=NUMBER' Use NUMBER characters for line numbers (default 6). `od': Write files in octal or other formats =========================================== `od' writes an unambiguous representation of each FILE (`-' means standard input), or standard input if none are given. Synopsis: od [OPTION]... [FILE]... od -C [FILE] [[+]OFFSET [[+]LABEL]] Each line of output consists of the offset in the input, followed by groups of data from the file. By default, `od' prints the offset in octal, and each group of file data is two bytes of input printed as a single octal number. The program accepts the following options. Also see *Note Common options::. `-A RADIX' `--address-radix=RADIX' Select the base in which file offsets are printed. RADIX can be one of the following: `d' decimal; `o' octal; `x' hexadecimal; `n' none (do not print offsets). The default is octal. `-j BYTES' `--skip-bytes=BYTES' Skip BYTES input bytes before formatting and writing. If BYTES begins with `0x' or `0X', it is interpreted in hexadecimal; otherwise, if it begins with `0', in octal; otherwise, in decimal. Appending `b' multiplies BYTES by 512, `k' by 1024, and `m' by 1048576. `-N BYTES' `--read-bytes=BYTES' Output at most BYTES bytes of the input. Prefixes and suffixes on `bytes' are interpreted as for the `-j' option. `-s [N]' `--strings[=N]' Instead of the normal output, output only "string constants": at least N (3 by default) consecutive ASCII graphic characters, followed by a null (zero) byte. `-t TYPE' `--format=TYPE' Select the format in which to output the file data. TYPE is a string of one or more of the below type indicator characters. If you include more than one type indicator character in a single TYPE string, or use this option more than once, `od' writes one copy of each output line using each of the data types that you specified, in the order that you specified. Adding a trailing "z" to any type specification appends a display of the ASCII character representation of the printable characters to the output line generated by the type specification. `a' named character, `c' ASCII character or backslash escape, `d' signed decimal, `f' floating point, `o' octal, `u' unsigned decimal, `x' hexadecimal. The type `a' outputs things like `sp' for space, `nl' for newline, and `nul' for a null (zero) byte. Type `c' outputs ` ', `\n', and `\0', respectively. Except for types `a' and `c', you can specify the number of bytes to use in interpreting each number in the given data type by following the type indicator character with a decimal integer. Alternately, you can specify the size of one of the C compiler's built-in data types by following the type indicator character with one of the following characters. For integers (`d', `o', `u', `x'): `C' char, `S' short, `I' int, `L' long. For floating point (`f'): F float, D double, L long double. `-v' `--output-duplicates' Output consecutive lines that are identical. By default, when two or more consecutive output lines would be identical, `od' outputs only the first line, and puts just an asterisk on the following line to indicate the elision. `-w[N]' `--width[=N]' Dump `n' input bytes per output line. This must be a multiple of the least common multiple of the sizes associated with the specified output types. If N is omitted, the default is 32. If this option is not given at all, the default is 16. The next several options map the old, pre-POSIX format specification options to the corresponding POSIX format specs. GNU `od' accepts any combination of old- and new-style options. Format specification options accumulate. `-a' Output as named characters. Equivalent to `-ta'. `-b' Output as octal bytes. Equivalent to `-toC'. `-c' Output as ASCII characters or backslash escapes. Equivalent to `-tc'. `-d' Output as unsigned decimal shorts. Equivalent to `-tu2'. `-f' Output as floats. Equivalent to `-tfF'. `-h' Output as hexadecimal shorts. Equivalent to `-tx2'. `-i' Output as decimal shorts. Equivalent to `-td2'. `-l' Output as decimal longs. Equivalent to `-td4'. `-o' Output as octal shorts. Equivalent to `-to2'. `-x' Output as hexadecimal shorts. Equivalent to `-tx2'. `-C' `--traditional' Recognize the pre-POSIX non-option arguments that traditional `od' accepted. The following syntax: od --traditional [FILE] [[+]OFFSET[.][b] [[+]LABEL[.][b]]] can be used to specify at most one file and optional arguments specifying an offset and a pseudo-start address, LABEL. By default, OFFSET is interpreted as an octal number specifying how many input bytes to skip before formatting and writing. The optional trailing decimal point forces the interpretation of OFFSET as a decimal number. If no decimal is specified and the offset begins with `0x' or `0X' it is interpreted as a hexadecimal number. If there is a trailing `b', the number of bytes skipped will be OFFSET multiplied by 512. The LABEL argument is interpreted just like OFFSET, but it specifies an initial pseudo-address. The pseudo-addresses are displayed in parentheses following any normal address. Formatting file contents ************************ These commands reformat the contents of files. `fmt': Reformat paragraph text ============================== `fmt' fills and joins lines to produce output lines of (at most) a given number of characters (75 by default). Synopsis: fmt [OPTION]... [FILE]... `fmt' reads from the specified FILE arguments (or standard input if none are given), and writes to standard output. By default, blank lines, spaces between words, and indentation are preserved in the output; successive input lines with different indentation are not joined; tabs are expanded on input and introduced on output. `fmt' prefers breaking lines at the end of a sentence, and tries to avoid line breaks after the first word of a sentence or before the last word of a sentence. A "sentence break" is defined as either the end of a paragraph or a word ending in any of `.?!', followed by two spaces or end of line, ignoring any intervening parentheses or quotes. Like TeX, `fmt' reads entire "paragraphs" before choosing line breaks; the algorithm is a variant of that in "Breaking Paragraphs Into Lines" (Donald E. Knuth and Michael F. Plass, `Software--Practice and Experience', 11 (1981), 1119-1184). The program accepts the following options. Also see *Note Common options::. `-c' `--crown-margin' "Crown margin" mode: preserve the indentation of the first two lines within a paragraph, and align the left margin of each subsequent line with that of the second line. `-t' `--tagged-paragraph' "Tagged paragraph" mode: like crown margin mode, except that if indentation of the first line of a paragraph is the same as the indentation of the second, the first line is treated as a one-line paragraph. `-s' `--split-only' Split lines only. Do not join short lines to form longer ones. This prevents sample lines of code, and other such "formatted" text from being unduly combined. `-u' `--uniform-spacing' Uniform spacing. Reduce spacing between words to one space, and spacing between sentences to two spaces. `-WIDTH' `-w WIDTH' `--width=WIDTH' Fill output lines up to WIDTH characters (default 75). `fmt' initially tries to make lines about 7% shorter than this, to give it room to balance line lengths. `-p PREFIX' `--prefix=PREFIX' Only lines beginning with PREFIX (possibly preceded by whitespace) are subject to formatting. The prefix and any preceding whitespace are stripped for the formatting and then re-attached to each formatted output line. One use is to format certain kinds of program comments, while leaving the code unchanged. `pr': Paginate or columnate files for printing ============================================== `pr' writes each FILE (`-' means standard input), or standard input if none are given, to standard output, paginating and optionally outputting in multicolumn format; optionally merges all FILEs, printing all in parallel, one per column. Synopsis: pr [OPTION]... [FILE]... By default, a 5-line header is printed at each page: two blank lines; a line with the date, the filename, and the page count; and two more blank lines. A footer of five blank lines is also printed. With the `-F' option, a 3-line header is printed: the leading two blank lines are omitted; no footer is used. The default PAGE_LENGTH in both cases is 66 lines. The default number of text lines changes from 56 (without `-F') to 63 (with `-F'). The text line of the header takes up the full PAGE_WIDTH in the form `yyyy-mm-dd HH:MM string Page nnnn'. String is a centered header string. Form feeds in the input cause page breaks in the output. Multiple form feeds produce empty pages. Columns are of equal width, separated by an optional string (default is `space'). For multicolumn output, lines will always be truncated to PAGE_WIDTH (default 72), unless you use the `-J' option. For single column output no line truncation occurs by default. Use `-W' option to truncate lines in that case. Including version 1.22i: Some small LETTER OPTIONS (`-s', `-w') has been redefined with the object of a better POSIX compliance. The output of some further cases has been adapted to other UNIXes. A violation of downward compatibility has to be accepted. Some NEW CAPITAL LETTER options (`-J', `-S', `-W') has been introduced to turn off unexpected interferences of small letter options. The `-N' option and the second argument LAST_PAGE of `+FIRST_PAGE' offer more flexibility. The detailed handling of form feeds set in the input files requires `-T' option. Capital letter options dominate small letter ones. Some of the option-arguments (compare `-s', `-S', `-e', `-i', `-n') cannot be specified as separate arguments from the preceding option letter (already stated in the POSIX specification). The program accepts the following options. Also see *Note Common options::. `+FIRST_PAGE[:LAST_PAGE]' `--pages=FIRST_PAGE[:LAST_PAGE]' Begin printing with page FIRST_PAGE and stop with LAST_PAGE. Missing `:LAST_PAGE' implies end of file. While estimating the number of skipped pages each form feed in the input file results in a new page. Page counting with and without `+FIRST_PAGE' is identical. By default, counting starts with the first page of input file (not first page printed). Line numbering may be altered by `-N' option. `-COLUMN' `--columns=COLUMN' With each single FILE, produce COLUMN columns of output (default is 1) and print columns down, unless `-a' is used. The column width is automatically decreased as COLUMN increases; unless you use the `-W/-w' option to increase PAGE_WIDTH as well. This option might well cause some lines to be truncated. The number of lines in the columns on each page are balanced. The options `-e' and `-i' are on for multiple text-column output. Together with `-J' option column alignment and line truncation is turned off. Lines of full length are joined in a free field format and `-S' option may set field separators. `-COLUMN' may not be used with `-m' option. `-a' `--across' With each single FILE, print columns across rather than down. The `-COLUMN' option must be given with COLUMN greater than one. If a line is too long to fit in a column, it is truncated. `-c' `--show-control-chars' Print control characters using hat notation (e.g., `^G'); print other unprintable characters in octal backslash notation. By default, unprintable characters are not changed. `-d' `--double-space' Double space the output. `-e[IN-TABCHAR[IN-TABWIDTH]]' `--expand-tabs[=IN-TABCHAR[IN-TABWIDTH]]' Expand TABs to spaces on input. Optional argument IN-TABCHAR is the input tab character (default is the TAB character). Second optional argument IN-TABWIDTH is the input tab character's width (default is 8). `-f' `-F' `--form-feed' Use a form feed instead of newlines to separate output pages. The default page length of 66 lines is not altered. But the number of lines of text per page changes from default 56 to 63 lines. `-h HEADER' `--header=HEADER' Replace the filename in the header with the centered string HEADER. Left-hand-side truncation (marked by a `*') may occur if the total header line `yyyy-mm-dd HH:MM HEADER Page nnnn' becomes larger than PAGE_WIDTH. `-h ""' prints a blank line header. Don't use `-h""'. A space between the `-h' option and the argument is always indispensable. `-i[OUT-TABCHAR[OUT-TABWIDTH]]' `--output-tabs[=OUT-TABCHAR[OUT-TABWIDTH]]' Replace spaces with TABs on output. Optional argument OUT-TABCHAR is the output tab character (default is the TAB character). Second optional argument OUT-TABWIDTH is the output tab character's width (default is 8). `-J' `--join-lines' Merge lines of full length. Used together with the column options `-COLUMN', `-a -COLUMN' or `-m'. Turns off `-W/-w' line truncation; no column alignment used; may be used with `-S[STRING]'. `-J' has been introduced (together with `-W' and `-S') to disentangle the old (POSIX compliant) options `-w' and `-s' along with the three column options. `-l PAGE_LENGTH' `--length=PAGE_LENGTH' Set the page length to PAGE_LENGTH (default 66) lines, including the lines of the header [and the footer]. If PAGE_LENGTH is less than or equal 10 (and <= 3 with `-F'), the header and footer are omitted, and all form feeds set in input files are eliminated, as if the `-T' option had been given. `-m' `--merge' Merge and print all FILEs in parallel, one in each column. If a line is too long to fit in a column, it is truncated, unless `-J' option is used. `-S[STRING]' may be used. Empty pages in some FILEs (form feeds set) produce empty columns, still marked by STRING. The result is a continuous line numbering and column marking throughout the whole merged file. Completely empty merged pages show no separators or line numbers. The default header becomes `yyyy-mm-dd HH:MM Page nnnn'; may be used with `-h HEADER' to fill up the middle blank part. `-n[NUMBER-SEPARATOR[DIGITS]]' `--number-lines[=NUMBER-SEPARATOR[DIGITS]]' Provide DIGITS digit line numbering (default for DIGITS is 5). With multicolumn output the number occupies the first DIGITS column positions of each text column or only each line of `-m' output. With single column output the number precedes each line just as `-m' does. Default counting of the line numbers starts with 1st line of the input file (not the 1st line printed, compare the `--page' option and `-N' option). Optional argument NUMBER-SEPARATOR is the character appended to the line number to separate it from the text followed. The default separator is the TAB character. In a strict sense a TAB is always printed with single column output only. The TAB-width varies with the TAB-position, e.g. with the left MARGIN specified by `-o' option. With multicolumn output priority is given to `equal width of output columns' (a POSIX specification). The TAB-width is fixed to the value of the 1st column and does not change with different values of left MARGIN. That means a fixed number of spaces is always printed in the place of the NUMBER-SEPARATOR TAB. The tabification depends upon the output position. `-N LINE_NUMBER' `--first-line-number=LINE_NUMBER' Start line counting with the number LINE_NUMBER at first line of first page printed (in most cases not the first line of the input file). `-o MARGIN' `--indent=MARGIN' Indent each line with a margin MARGIN spaces wide (default is zero). The total page width is the size of the margin plus the PAGE_WIDTH set with the `-W/-w' option. A limited overflow may occur with numbered single column output (compare `-n' option). `-r' `--no-file-warnings' Do not print a warning message when an argument FILE cannot be opened. (The exit status will still be nonzero, however.) `-s[CHAR]' `--separator[=CHAR]' Separate columns by a single character CHAR. Default for CHAR is the TAB character without `-w' and `no character' with `-w'. Without `-s' default separator `space' is set. `-s[char]' turns off line truncation of all three column options (`-COLUMN'|`-a -COLUMN'|`-m') except `-w' is set. That is a POSIX compliant formulation. `-S[STRING]' `--sep-string[=STRING]' Use STRING to separate output columns. The `-S' option doesn't affect the `-W/-w' option, unlike the `-s' option which does. It does not affect line truncation or column alignment. Without `-S', and with `-J', `pr' uses the default output separator, TAB. Without `-S' or `-J', `pr' uses a `space' (same as `-S" "'). Using `-S' with no STRING is equivalent to `-S""'. Note that for some of `pr''s options the single-letter option character must be followed immediately by any corresponding argument; there may not be any intervening white space. `-S/-s' is one of them. Don't use `-S "STRING"'. POSIX requires this. `-t' `--omit-header' Do not print the usual header [and footer] on each page, and do not fill out the bottom of pages (with blank lines or a form feed). No page structure is produced, but form feeds set in the input files are retained. The predefined pagination is not changed. `-t' or `-T' may be useful together with other options; e.g.: `-t -e4', expand TAB characters in the input file to 4 spaces but don't make any other changes. Use of `-t' overrides `-h'. `-T' `--omit-pagination' Do not print header [and footer]. In addition eliminate all form feeds set in the input files. `-v' `--show-nonprinting' Print unprintable characters in octal backslash notation. `-w PAGE_WIDTH' `--width=PAGE_WIDTH' Set page width to PAGE_WIDTH characters for multiple text-column output only (default for PAGE_WIDTH is 72). `-s[CHAR]' turns off the default page width and any line truncation and column alignment. Lines of full length are merged, regardless of the column options set. No PAGE_WIDTH setting is possible with single column output. A POSIX compliant formulation. `-W PAGE_WIDTH' `--page_width=PAGE_WIDTH' Set the page width to PAGE_WIDTH characters. That's valid with and without a column option. Text lines are truncated, unless `-J' is used. Together with one of the three column options (`-COLUMN', `-a -COLUMN' or `-m') column alignment is always used. The separator options `-S' or `-s' don't affect the `-W' option. Default is 72 characters. Without `-W PAGE_WIDTH' and without any of the column options NO line truncation is used (defined to keep downward compatibility and to meet most frequent tasks). That's equivalent to `-W 72 -J'. With and without `-W PAGE_WIDTH' the header line is always truncated to avoid line overflow. `fold': Wrap input lines to fit in specified width ================================================== `fold' writes each FILE (`-' means standard input), or standard input if none are given, to standard output, breaking long lines. Synopsis: fold [OPTION]... [FILE]... By default, `fold' breaks lines wider than 80 columns. The output is split into as many lines as necessary. `fold' counts screen columns by default; thus, a tab may count more than one column, backspace decreases the column count, and carriage return sets the column to zero. The program accepts the following options. Also see *Note Common options::. `-b' `--bytes' Count bytes rather than columns, so that tabs, backspaces, and carriage returns are each counted as taking up one column, just like other characters. `-s' `--spaces' Break at word boundaries: the line is broken after the last blank before the maximum line length. If the line contains no such blanks, the line is broken at the maximum line length as usual. `-w WIDTH' `--width=WIDTH' Use a maximum line length of WIDTH columns instead of 80. Output of parts of files ************************ These commands output pieces of the input. `head': Output the first part of files ====================================== `head' prints the first part (10 lines by default) of each FILE; it reads from standard input if no files are given or when given a FILE of `-'. Synopses: head [OPTION]... [FILE]... head -NUMBER [OPTION]... [FILE]... If more than one FILE is specified, `head' prints a one-line header consisting of ==> FILE NAME <== before the output for each FILE. `head' accepts two option formats: the new one, in which numbers are arguments to the options (`-q -n 1'), and the old one, in which the number precedes any option letters (`-1q'). The program accepts the following options. Also see *Note Common options::. `-COUNTOPTIONS' This option is only recognized if it is specified first. COUNT is a decimal number optionally followed by a size letter (`b', `k', `m') as in `-c', or `l' to mean count by lines, or other option letters (`cqv'). `-c BYTES' `--bytes=BYTES' Print the first BYTES bytes, instead of initial lines. Appending `b' multiplies BYTES by 512, `k' by 1024, and `m' by 1048576. `-n N' `--lines=N' Output the first N lines. `-q' `--quiet' `--silent' Never print file name headers. `-v' `--verbose' Always print file name headers. `tail': Output the last part of files ===================================== `tail' prints the last part (10 lines by default) of each FILE; it reads from standard input if no files are given or when given a FILE of `-'. Synopses: tail [OPTION]... [FILE]... tail -NUMBER [OPTION]... [FILE]... tail +NUMBER [OPTION]... [FILE]... If more than one FILE is specified, `tail' prints a one-line header consisting of ==> FILE NAME <== before the output for each FILE. GNU `tail' can output any amount of data (some other versions of `tail' cannot). It also has no `-r' option (print in reverse), since reversing a file is really a different job from printing the end of a file; BSD `tail' (which is the one with `-r') can only reverse files that are at most as large as its buffer, which is typically 32k. A more reliable and versatile way to reverse files is the GNU `tac' command. `tail' accepts two option formats: the new one, in which numbers are arguments to the options (`-n 1'), and the old one, in which the number precedes any option letters (`-1' or `+1'). If any option-argument is a number N starting with a `+', `tail' begins printing with the Nth item from the start of each file, instead of from the end. The program accepts the following options. Also see *Note Common options::. `-COUNT' `+COUNT' This option is only recognized if it is specified first. COUNT is a decimal number optionally followed by a size letter (`b', `k', `m') as in `-c', or `l' to mean count by lines, or other option letters (`cfqv'). `-c BYTES' `--bytes=BYTES' Output the last BYTES bytes, instead of final lines. Appending `b' multiplies BYTES by 512, `k' by 1024, and `m' by 1048576. `-f' `--follow[=HOW]' Loop forever trying to read more characters at the end of the file, presumably because the file is growing. This option is ignored when reading from a pipe. If more than one file is given, `tail' prints a header whenever it gets output from a different file, to indicate which file that output is from. There are two ways to specify how you'd like to track files with this option, but that difference is noticeable only when a followed file is removed or renamed. If you'd like to continue to track the end of a growing file even after it has been unlinked, use `--follow=descriptor'. This is the default behavior, but it is not useful if you're tracking a log file that may be rotated (removed or renamed, then reopened). In that case, use `--follow=name' to track the named file by reopening it periodically to see if it has been removed and recreated by some other program. No matter which method you use, if the tracked file is determined to have shrunk, `tail' prints a message saying the file has been truncated and resumes tracking the end of the file from the newly-determined endpoint. When a file is removed, `tail''s behavior depends on whether it is following the name or the descriptor. When following by name, tail can detect that a file has been removed and gives a message to that effect, and if `--retry' has been specified it will continue checking periodically to see if the file reappears. When following a descriptor, tail does not detect that the file has been unlinked or renamed and issues no message; even though the file may no longer be accessible via its original name, it may still be growing. The option values `descriptor' and `name' may be specified only with the long form of the option, not with `-f'. `--retry' This option is meaningful only when following by name. Without this option, when tail encounters a file that doesn't exist or is otherwise inaccessible, it reports that fact and never checks it again. `--sleep-interval=N' Change the number of seconds to wait between iterations (the default is 1). During one iteration, every specified file is checked to see if it has changed size. `--pid=PID' When following by name or by descriptor, you may specify the process ID, PID, of the sole writer of all FILE arguments. Then, shortly after that process terminates, tail will also terminate. This will work properly only if the writer and the tailing process are running on the same machine. For example, to save the output of a build in a file and to watch the file grow, if you invoke `make' and `tail' like this then the tail process will stop when your build completes. Without this option, you would have had to kill the `tail -f' process yourself. $ make >& makerr & tail --pid=$! -f makerr If you specify a PID that is not in use or that does not correspond to the process that is writing to the tailed files, then `tail' may terminate long before any FILEs stop growing or it may not terminate until long after the real writer has terminated. `--max-consecutive-size-changes=N' This option is meaningful only when following by name. Use it to control how long `tail' follows the descriptor of a file that continues growing at a rapid pace even after it is deleted or renamed. After detecting N consecutive size changes for a file, `open'/`fstat' the file to determine if that file name is still associated with the same device/inode-number pair as before. See the output of `tail --help' for the default value. `--max-unchanged-stats=N' When tailing a file by name, if there have been this many consecutive iterations for which the size has remained the same, then `open'/`fstat' the file to determine if that file name is still associated with the same device/inode-number pair as before. When following a log file that is rotated this is approximately the number of seconds between when tail prints the last pre-rotation lines and when it prints the lines that have accumulated in the new log file. See the output of `tail --help' for the default value. This option is meaningful only when following by name. `-n N' `--lines=N' Output the last N lines. `-q' `-quiet' `--silent' Never print file name headers. `-v' `--verbose' Always print file name headers. `split': Split a file into fixed-size pieces ============================================ `split' creates output files containing consecutive sections of INPUT (standard input if none is given or INPUT is `-'). Synopsis: split [OPTION] [INPUT [PREFIX]] By default, `split' puts 1000 lines of INPUT (or whatever is left over for the last section), into each output file. The output files' names consist of PREFIX (`x' by default) followed by a group of letters `aa', `ab', and so on, such that concatenating the output files in sorted order by file name produces the original input file. (If more than 676 output files are required, `split' uses `zaa', `zab', etc.) The program accepts the following options. Also see *Note Common options::. `-LINES' `-l LINES' `--lines=LINES' Put LINES lines of INPUT into each output file. `-b BYTES' `--bytes=BYTES' Put the first BYTES bytes of INPUT into each output file. Appending `b' multiplies BYTES by 512, `k' by 1024, and `m' by 1048576. `-C BYTES' `--line-bytes=BYTES' Put into each output file as many complete lines of INPUT as possible without exceeding BYTES bytes. For lines longer than BYTES bytes, put BYTES bytes into each output file until less than BYTES bytes of the line are left, then continue normally. BYTES has the same format as for the `--bytes' option. `--verbose' Write a diagnostic to standard error just before each output file is opened. `csplit': Split a file into context-determined pieces ===================================================== `csplit' creates zero or more output files containing sections of INPUT (standard input if INPUT is `-'). Synopsis: csplit [OPTION]... INPUT PATTERN... The contents of the output files are determined by the PATTERN arguments, as detailed below. An error occurs if a PATTERN argument refers to a nonexistent line of the input file (e.g., if no remaining line matches a given regular expression). After every PATTERN has been matched, any remaining input is copied into one last output file. By default, `csplit' prints the number of bytes written to each output file after it has been created. The types of pattern arguments are: `N' Create an output file containing the input up to but not including line N (a positive integer). If followed by a repeat count, also create an output file containing the next LINE lines of the input file once for each repeat. `/REGEXP/[OFFSET]' Create an output file containing the current line up to (but not including) the next line of the input file that contains a match for REGEXP. The optional OFFSET is a `+' or `-' followed by a positive integer. If it is given, the input up to the matching line plus or minus OFFSET is put into the output file, and the line after that begins the next section of input. `%REGEXP%[OFFSET]' Like the previous type, except that it does not create an output file, so that section of the input file is effectively ignored. `{REPEAT-COUNT}' Repeat the previous pattern REPEAT-COUNT additional times. REPEAT-COUNT can either be a positive integer or an asterisk, meaning repeat as many times as necessary until the input is exhausted. The output files' names consist of a prefix (`xx' by default) followed by a suffix. By default, the suffix is an ascending sequence of two-digit decimal numbers from `00' and up to `99'. In any case, concatenating the output files in sorted order by filename produces the original input file. By default, if `csplit' encounters an error or receives a hangup, interrupt, quit, or terminate signal, it removes any output files that it has created so far before it exits. The program accepts the following options. Also see *Note Common options::. `-f PREFIX' `--prefix=PREFIX' Use PREFIX as the output file name prefix. `-b SUFFIX' `--suffix=SUFFIX' Use SUFFIX as the output file name suffix. When this option is specified, the suffix string must include exactly one `printf(3)'-style conversion specification, possibly including format specification flags, a field width, a precision specifications, or all of these kinds of modifiers. The format letter must convert a binary integer argument to readable form; thus, only `d', `i', `u', `o', `x', and `X' conversions are allowed. The entire SUFFIX is given (with the current output file number) to `sprintf(3)' to form the file name suffixes for each of the individual output files in turn. If this option is used, the `--digits' option is ignored. `-n DIGITS' `--digits=DIGITS' Use output file names containing numbers that are DIGITS digits long instead of the default 2. `-k' `--keep-files' Do not remove output files when errors are encountered. `-z' `--elide-empty-files' Suppress the generation of zero-length output files. (In cases where the section delimiters of the input file are supposed to mark the first lines of each of the sections, the first output file will generally be a zero-length file unless you use this option.) The output file sequence numbers always run consecutively starting from 0, even when this option is specified. `-s' `-q' `--silent' `--quiet' Do not print counts of output file sizes. Summarizing files ***************** These commands generate just a few numbers representing entire contents of files. `wc': Print byte, word, and line counts ======================================= `wc' counts the number of bytes, whitespace-separated words, and newlines in each given FILE, or standard input if none are given or for a FILE of `-'. Synopsis: wc [OPTION]... [FILE]... `wc' prints one line of counts for each file, and if the file was given as an argument, it prints the file name following the counts. If more than one FILE is given, `wc' prints a final line containing the cumulative counts, with the file name `total'. The counts are printed in this order: newlines, words, bytes. By default, each count is output right-justified in a 7-byte field with one space between fields so that the numbers and file names line up nicely in columns. However, POSIX requires that there be exactly one space separating columns. You can make `wc' use the POSIX-mandated output format by setting the `POSIXLY_CORRECT' environment variable. By default, `wc' prints all three counts. Options can specify that only certain counts be printed. Options do not undo others previously given, so wc --bytes --words prints both the byte counts and the word counts. With the `--max-line-length' option, `wc' prints the length of the longest line per file, and if there is more than one file it prints the maximum (not the sum) of those lengths. The program accepts the following options. Also see *Note Common options::. `-c' `--bytes' `--chars' Print only the byte counts. `-w' `--words' Print only the word counts. `-l' `--lines' Print only the newline counts. `-L' `--max-line-length' Print only the maximum line lengths. `sum': Print checksum and block counts ====================================== `sum' computes a 16-bit checksum for each given FILE, or standard input if none are given or for a FILE of `-'. Synopsis: sum [OPTION]... [FILE]... `sum' prints the checksum for each FILE followed by the number of blocks in the file (rounded up). If more than one FILE is given, file names are also printed (by default). (With the `--sysv' option, corresponding file name are printed when there is at least one file argument.) By default, GNU `sum' computes checksums using an algorithm compatible with BSD `sum' and prints file sizes in units of 1024-byte blocks. The program accepts the following options. Also see *Note Common options::. `-r' Use the default (BSD compatible) algorithm. This option is included for compatibility with the System V `sum'. Unless `-s' was also given, it has no effect. `-s' `--sysv' Compute checksums using an algorithm compatible with System V `sum''s default, and print file sizes in units of 512-byte blocks. `sum' is provided for compatibility; the `cksum' program (see next section) is preferable in new applications. `cksum': Print CRC checksum and byte counts =========================================== `cksum' computes a cyclic redundancy check (CRC) checksum for each given FILE, or standard input if none are given or for a FILE of `-'. Synopsis: cksum [OPTION]... [FILE]... `cksum' prints the CRC checksum for each file along with the number of bytes in the file, and the filename unless no arguments were given. `cksum' is typically used to ensure that files transferred by unreliable means (e.g., netnews) have not been corrupted, by comparing the `cksum' output for the received files with the `cksum' output for the original files (typically given in the distribution). The CRC algorithm is specified by the POSIX.2 standard. It is not compatible with the BSD or System V `sum' algorithms (see the previous section); it is more robust. The only options are `--help' and `--version'. *Note Common options::. `md5sum': Print or check message-digests ======================================== `md5sum' computes a 128-bit checksum (or "fingerprint" or "message-digest") for each specified FILE. If a FILE is specified as `-' or if no files are given `md5sum' computes the checksum for the standard input. `md5sum' can also determine whether a file and checksum are consistent. Synopses: md5sum [OPTION]... [FILE]... md5sum [OPTION]... --check [FILE] For each FILE, `md5sum' outputs the MD5 checksum, a flag indicating a binary or text input file, and the filename. If FILE is omitted or specified as `-', standard input is read. The program accepts the following options. Also see *Note Common options::. `-b' `--binary' Treat all input files as binary. This option has no effect on Unix systems, since they don't distinguish between binary and text files. This option is useful on systems that have different internal and external character representations. On MS-DOS and MS-Windows, this is the default. `-c' `--check' Read filenames and checksum information from the single FILE (or from stdin if no FILE was specified) and report whether each named file and the corresponding checksum data are consistent. The input to this mode of `md5sum' is usually the output of a prior, checksum-generating run of `md5sum'. Each valid line of input consists of an MD5 checksum, a binary/text flag, and then a filename. Binary files are marked with `*', text with ` '. For each such line, `md5sum' reads the named file and computes its MD5 checksum. Then, if the computed message digest does not match the one on the line with the filename, the file is noted as having failed the test. Otherwise, the file passes the test. By default, for each valid line, one line is written to standard output indicating whether the named file passed the test. After all checks have been performed, if there were any failures, a warning is issued to standard error. Use the `--status' option to inhibit that output. If any listed file cannot be opened or read, if any valid line has an MD5 checksum inconsistent with the associated file, or if no valid line is found, `md5sum' exits with nonzero status. Otherwise, it exits successfully. `--status' This option is useful only when verifying checksums. When verifying checksums, don't generate the default one-line-per-file diagnostic and don't output the warning summarizing any failures. Failures to open or read a file still evoke individual diagnostics to standard error. If all listed files are readable and are consistent with the associated MD5 checksums, exit successfully. Otherwise exit with a status code indicating there was a failure. `-t' `--text' Treat all input files as text files. This is the reverse of `--binary'. `-w' `--warn' When verifying checksums, warn about improperly formatted MD5 checksum lines. This option is useful only if all but a few lines in the checked input are valid. Operating on sorted files ************************* These commands work with (or produce) sorted files. `sort': Sort text files ======================= `sort' sorts, merges, or compares all the lines from the given files, or standard input if none are given or for a FILE of `-'. By default, `sort' writes the results to standard output. Synopsis: sort [OPTION]... [FILE]... `sort' has three modes of operation: sort (the default), merge, and check for sortedness. The following options change the operation mode: `-c' Check whether the given files are already sorted: if they are not all sorted, print an error message and exit with a status of 1. Otherwise, exit successfully. `-m' Merge the given files by sorting them as a group. Each input file must always be individually sorted. It always works to sort instead of merge; merging is provided because it is faster, in the case where it works. A pair of lines is compared as follows: if any key fields have been specified, `sort' compares each pair of fields, in the order specified on the command line, according to the associated ordering options, until a difference is found or no fields are left. Unless otherwise specified, all comparisons use the character collating sequence specified by the `LC_COLLATE' locale. If any of the global options `Mbdfinr' are given but no key fields are specified, `sort' compares the entire lines according to the global options. Finally, as a last resort when all keys compare equal (or if no ordering options were specified at all), `sort' compares the entire lines. The last resort comparison honors the `-r' global option. The `-s' (stable) option disables this last-resort comparison so that lines in which all fields compare equal are left in their original relative order. If no fields or global options are specified, `-s' has no effect. GNU `sort' (as specified for all GNU utilities) has no limits on input line length or restrictions on bytes allowed within lines. In addition, if the final byte of an input file is not a newline, GNU `sort' silently supplies one. A line's trailing newline is part of the line for comparison purposes; for example, with no options in an ASCII locale, a line starting with a tab sorts before an empty line because tab precedes newline in the ASCII collating sequence. Upon any error, `sort' exits with a status of `2'. If the environment variable `TMPDIR' is set, `sort' uses its value as the directory for temporary files instead of `/tmp'. The `-T TEMPDIR' option in turn overrides the environment variable. The following options affect the ordering of output lines. They may be specified globally or as part of a specific key field. If no key fields are specified, global options apply to comparison of entire lines; otherwise the global options are inherited by key fields that do not specify any special options of their own. The `-b', `-d', `-f' and `-i' options classify characters according to the `LC_CTYPE' locale. `-b' Ignore leading blanks when finding sort keys in each line. `-d' Sort in "phone directory" order: ignore all characters except letters, digits and blanks when sorting. `-f' Fold lowercase characters into the equivalent uppercase characters when sorting so that, for example, `b' and `B' sort as equal. `-g' Sort numerically, using the standard C function `strtod' to convert a prefix of each line to a double-precision floating point number. This allows floating point numbers to be specified in scientific notation, like `1.0e-34' and `10e100'. Do not report overflow, underflow, or conversion errors. Use the following collating sequence: * Lines that do not start with numbers (all considered to be equal). * NaNs ("Not a Number" values, in IEEE floating point arithmetic) in a consistent but machine-dependent order. * Minus infinity. * Finite numbers in ascending numeric order (with -0 and +0 equal). * Plus infinity. Use this option only if there is no alternative; it is much slower than `-n' and it can lose information when converting to floating point. `-i' Ignore unprintable characters. `-M' An initial string, consisting of any amount of whitespace, followed by a month name abbreviation, is folded to UPPER case and compared in the order `JAN' < `FEB' < ... < `DEC'. Invalid names compare low to valid names. The `LC_TIME' locale determines the month spellings. `-n' Sort numerically: the number begins each line; specifically, it consists of optional whitespace, an optional `-' sign, and zero or more digits possibly separated by thousands separators, optionally followed by a radix character and zero or more digits. The `LC_NUMERIC' locale specifies the radix character and thousands separator. `sort -n' uses what might be considered an unconventional method to compare strings representing floating point numbers. Rather than first converting each string to the C `double' type and then comparing those values, sort aligns the radix characters in the two strings and compares the strings a character at a time. One benefit of using this approach is its speed. In practice this is much more efficient than performing the two corresponding string-to-double (or even string-to-integer) conversions and then comparing doubles. In addition, there is no corresponding loss of precision. Converting each string to `double' before comparison would limit precision to about 16 digits on most systems. Neither a leading `+' nor exponential notation is recognized. To compare such strings numerically, use the `-g' option. `-r' Reverse the result of comparison, so that lines with greater key values appear earlier in the output instead of later. Other options are: `-o OUTPUT-FILE' Write output to OUTPUT-FILE instead of standard output. If OUTPUT-FILE is one of the input files, `sort' copies it to a temporary file before sorting and writing the output to OUTPUT-FILE. `-t SEPARATOR' Use character SEPARATOR as the field separator when finding the sort keys in each line. By default, fields are separated by the empty string between a non-whitespace character and a whitespace character. That is, given the input line ` foo bar', `sort' breaks it into fields ` foo' and ` bar'. The field separator is not considered to be part of either the field preceding or the field following. `-u' For the default case or the `-m' option, only output the first of a sequence of lines that compare equal. For the `-c' option, check that no pair of consecutive lines compares equal. `-k POS1[,POS2]' The recommended, POSIX, option for specifying a sort field. The field consists of the part of the line between POS1 and POS2 (or the end of the line, if POS2 is omitted), _inclusive_. Fields and character positions are numbered starting with 1. So to sort on the second field, you'd use `-k 2,2' See below for more examples. `-z' Treat the input as a set of lines, each terminated by a zero byte (ASCII NUL (Null) character) instead of an ASCII LF (Line Feed). This option can be useful in conjunction with `perl -0' or `find -print0' and `xargs -0' which do the same in order to reliably handle arbitrary pathnames (even those which contain Line Feed characters.) `+POS1[-POS2]' The obsolete, traditional option for specifying a sort field. The field consists of the line between POS1 and up to but _not including_ POS2 (or the end of the line if POS2 is omitted). Fields and character positions are numbered starting with 0. See below. In addition, when GNU `sort' is invoked with exactly one argument, options `--help' and `--version' are recognized. *Note Common options::. Historical (BSD and System V) implementations of `sort' have differed in their interpretation of some options, particularly `-b', `-f', and `-n'. GNU sort follows the POSIX behavior, which is usually (but not always!) like the System V behavior. According to POSIX, `-n' no longer implies `-b'. For consistency, `-M' has been changed in the same way. This may affect the meaning of character positions in field specifications in obscure cases. The only fix is to add an explicit `-b'. A position in a sort field specified with the `-k' or `+' option has the form `F.C', where F is the number of the field to use and C is the number of the first character from the beginning of the field (for `+POS') or from the end of the previous field (for `-POS'). If the `.C' is omitted, it is taken to be the first character in the field. If the `-b' option was specified, the `.C' part of a field specification is counted from the first nonblank character of the field (for `+POS') or from the first nonblank character following the previous field (for `-POS'). A sort key option may also have any of the option letters `Mbdfinr' appended to it, in which case the global ordering options are not used for that particular field. The `-b' option may be independently attached to either or both of the `+POS' and `-POS' parts of a field specification, and if it is inherited from the global options it will be attached to both. Keys may span multiple fields. Here are some examples to illustrate various combinations of options. In them, the POSIX `-k' option is used to specify sort keys rather than the obsolete `+POS1-POS2' syntax. * Sort in descending (reverse) numeric order. sort -nr Sort alphabetically, omitting the first and second fields. This uses a single key composed of the characters beginning at the start of field three and extending to the end of each line. sort -k3 * Sort numerically on the second field and resolve ties by sorting alphabetically on the third and fourth characters of field five. Use `:' as the field delimiter. sort -t : -k 2,2n -k 5.3,5.4 Note that if you had written `-k 2' instead of `-k 2,2' `sort' would have used all characters beginning in the second field and extending to the end of the line as the primary _numeric_ key. For the large majority of applications, treating keys spanning more than one field as numeric will not do what you expect. Also note that the `n' modifier was applied to the field-end specifier for the first key. It would have been equivalent to specify `-k 2n,2' or `-k 2n,2n'. All modifiers except `b' apply to the associated _field_, regardless of whether the modifier character is attached to the field-start and/or the field-end part of the key specifier. * Sort the password file on the fifth field and ignore any leading white space. Sort lines with equal values in field five on the numeric user ID in field three. sort -t : -k 5b,5 -k 3,3n /etc/passwd An alternative is to use the global numeric modifier `-n'. sort -t : -n -k 5b,5 -k 3,3 /etc/passwd * Generate a tags file in case insensitive sorted order. find src -type f -print0 | sort -t / -z -f | xargs -0 etags --append The use of `-print0', `-z', and `-0' in this case mean that pathnames that contain Line Feed characters will not get broken up by the sort operation. Finally, to ignore both leading and trailing white space, you could have applied the `b' modifier to the field-end specifier for the first key, sort -t : -n -k 5b,5b -k 3,3 /etc/passwd or by using the global `-b' modifier instead of `-n' and an explicit `n' with the second key specifier. sort -t : -b -k 5,5 -k 3,3n /etc/passwd `uniq': Uniquify files ====================== `uniq' writes the unique lines in the given `input', or standard input if nothing is given or for an INPUT name of `-'. Synopsis: uniq [OPTION]... [INPUT [OUTPUT]] By default, `uniq' prints the unique lines in a sorted file, i.e., discards all but one of identical successive lines. Optionally, it can instead show only lines that appear exactly once, or lines that appear more than once. The input must be sorted. If your input is not sorted, perhaps you want to use `sort -u'. If no OUTPUT file is specified, `uniq' writes to standard output. The program accepts the following options. Also see *Note Common options::. `-N' `-f N' `--skip-fields=N' Skip N fields on each line before checking for uniqueness. Fields are sequences of non-space non-tab characters that are separated from each other by at least one spaces or tabs. `+N' `-s N' `--skip-chars=N' Skip N characters before checking for uniqueness. If you use both the field and character skipping options, fields are skipped over first. `-c' `--count' Print the number of times each line occurred along with the line. `-i' `--ignore-case' Ignore differences in case when comparing lines. `-d' `--repeated' Print only duplicate lines. `-D' `--all-repeated' Print all duplicate lines and only duplicate lines. This option is useful mainly in conjunction with other options e.g., to ignore case or to compare only selected fields. This is a GNU extension. `-u' `--unique' Print only unique lines. `-w N' `--check-chars=N' Compare N characters on each line (after skipping any specified fields and characters). By default the entire rest of the lines are compared. `comm': Compare two sorted files line by line ============================================= `comm' writes to standard output lines that are common, and lines that are unique, to two input files; a file name of `-' means standard input. Synopsis: comm [OPTION]... FILE1 FILE2 Before `comm' can be used, the input files must be sorted using the collating sequence specified by the `LC_COLLATE' locale, with trailing newlines significant. If an input file ends in a non-newline character, a newline is silently appended. The `sort' command with no options always outputs a file that is suitable input to `comm'. With no options, `comm' produces three column output. Column one contains lines unique to FILE1, column two contains lines unique to FILE2, and column three contains lines common to both files. Columns are separated by a single TAB character. The options `-1', `-2', and `-3' suppress printing of the corresponding columns. Also see *Note Common options::. Unlike some other comparison utilities, `comm' has an exit status that does not depend on the result of the comparison. Upon normal completion `comm' produces an exit code of zero. If there is an error it exits with nonzero status. `tsort': Topological sort ========================= `tsort' performs a topological sort on the given FILE, or standard input if no input file is given or for a FILE of `-'. Synopsis: tsort [OPTION] [FILE] `tsort' reads its input as pairs of strings, separated by blanks, indicating a partial ordering. The output is a total ordering that corresponds to the given partial ordering. For example tsort < final.pretty.data We start out by creating the raw data; each filter applies some successive transformation to the data, until by the time it comes out of the pipeline, it is in the desired form. This is fine and good for standard input and standard output. Where does the standard error come in to play? Well, think about `filter1' in the pipeline above. What happens if it encounters an error in the data it sees? If it writes an error message to standard output, it will just disappear down the pipeline into `filter2''s input, and the user will probably never see it. So programs need a place where they can send error messages so that the user will notice them. This is standard error, and it is usually connected to your console or window, even if you have redirected standard output of your program away from your screen. For filter programs to work together, the format of the data has to be agreed upon. The most straightforward and easiest format to use is simply lines of text. Unix data files are generally just streams of bytes, with lines delimited by the ASCII LF (Line Feed) character, conventionally called a "newline" in the Unix literature. (This is `'\n'' if you're a C programmer.) This is the format used by all the traditional filtering programs. (Many earlier operating systems had elaborate facilities and special purpose programs for managing binary data. Unix has always shied away from such things, under the philosophy that it's easiest to simply be able to view and edit your data with a text editor.) OK, enough introduction. Let's take a look at some of the tools, and then we'll see how to hook them together in interesting ways. In the following discussion, we will only present those command line options that interest us. As you should always do, double check your system documentation for the full story. The `who' command ================= The first program is the `who' command. By itself, it generates a list of the users who are currently logged in. Although I'm writing this on a single-user system, we'll pretend that several people are logged in: $ who arnold console Jan 22 19:57 miriam ttyp0 Jan 23 14:19(:0.0) bill ttyp1 Jan 21 09:32(:0.0) arnold ttyp2 Jan 23 20:48(:0.0) Here, the `$' is the usual shell prompt, at which I typed `who'. There are three people logged in, and I am logged in twice. On traditional Unix systems, user names are never more than eight characters long. This little bit of trivia will be useful later. The output of `who' is nice, but the data is not all that exciting. The `cut' command ================= The next program we'll look at is the `cut' command. This program cuts out columns or fields of input data. For example, we can tell it to print just the login name and full name from the `/etc/passwd file'. The `/etc/passwd' file has seven fields, separated by colons: arnold:xyzzy:2076:10:Arnold D. Robbins:/home/arnold:/bin/ksh To get the first and fifth fields, we would use cut like this: $ cut -d: -f1,5 /etc/passwd root:Operator ... arnold:Arnold D. Robbins miriam:Miriam A. Robbins ... With the `-c' option, `cut' will cut out specific characters (i.e., columns) in the input lines. This command looks like it might be useful for data filtering. The `sort' command ================== Next we'll look at the `sort' command. This is one of the most powerful commands on a Unix-style system; one that you will often find yourself using when setting up fancy data plumbing. The `sort' command reads and sorts each file named on the command line. It then merges the sorted data and writes it to standard output. It will read standard input if no files are given on the command line (thus making it into a filter). The sort is based on the character collating sequence or based on user-supplied ordering criteria. The `uniq' command ================== Finally (at least for now), we'll look at the `uniq' program. When sorting data, you will often end up with duplicate lines, lines that are identical. Usually, all you need is one instance of each line. This is where `uniq' comes in. The `uniq' program reads its standard input, which it expects to be sorted. It only prints out one copy of each duplicated line. It does have several options. Later on, we'll use the `-c' option, which prints each unique line, preceded by a count of the number of times that line occurred in the input. Putting the tools together ========================== Now, let's suppose this is a large BBS system with dozens of users logged in. The management wants the SysOp to write a program that will generate a sorted list of logged in users. Furthermore, even if a user is logged in multiple times, his or her name should only show up in the output once. The SysOp could sit down with the system documentation and write a C program that did this. It would take perhaps a couple of hundred lines of code and about two hours to write it, test it, and debug it. However, knowing the software toolbox, the SysOp can instead start out by generating just a list of logged on users: $ who | cut -c1-8 arnold miriam bill arnold Next, sort the list: $ who | cut -c1-8 | sort arnold arnold bill miriam Finally, run the sorted list through `uniq', to weed out duplicates: $ who | cut -c1-8 | sort | uniq arnold bill miriam The `sort' command actually has a `-u' option that does what `uniq' does. However, `uniq' has other uses for which one cannot substitute `sort -u'. The SysOp puts this pipeline into a shell script, and makes it available for all the users on the system: # cat > /usr/local/bin/listusers who | cut -c1-8 | sort | uniq ^D # chmod +x /usr/local/bin/listusers There are four major points to note here. First, with just four programs, on one command line, the SysOp was able to save about two hours worth of work. Furthermore, the shell pipeline is just about as efficient as the C program would be, and it is much more efficient in terms of programmer time. People time is much more expensive than computer time, and in our modern "there's never enough time to do everything" society, saving two hours of programmer time is no mean feat. Second, it is also important to emphasize that with the _combination_ of the tools, it is possible to do a special purpose job never imagined by the authors of the individual programs. Third, it is also valuable to build up your pipeline in stages, as we did here. This allows you to view the data at each stage in the pipeline, which helps you acquire the confidence that you are indeed using these tools correctly. Finally, by bundling the pipeline in a shell script, other users can use your command, without having to remember the fancy plumbing you set up for them. In terms of how you run them, shell scripts and compiled programs are indistinguishable. After the previous warm-up exercise, we'll look at two additional, more complicated pipelines. For them, we need to introduce two more tools. The first is the `tr' command, which stands for "transliterate." The `tr' command works on a character-by-character basis, changing characters. Normally it is used for things like mapping upper case to lower case: $ echo ThIs ExAmPlE HaS MIXED case! | tr '[A-Z]' '[a-z]' this example has mixed case! There are several options of interest: `-c' work on the complement of the listed characters, i.e., operations apply to characters not in the given set `-d' delete characters in the first set from the output `-s' squeeze repeated characters in the output into just one character. We will be using all three options in a moment. The other command we'll look at is `comm'. The `comm' command takes two sorted input files as input data, and prints out the files' lines in three columns. The output columns are the data lines unique to the first file, the data lines unique to the second file, and the data lines that are common to both. The `-1', `-2', and `-3' command line options omit the respective columns. (This is non-intuitive and takes a little getting used to.) For example: $ cat f1 11111 22222 33333 44444 $ cat f2 00000 22222 33333 55555 $ comm f1 f2 00000 11111 22222 33333 44444 55555 The single dash as a filename tells `comm' to read standard input instead of a regular file. Now we're ready to build a fancy pipeline. The first application is a word frequency counter. This helps an author determine if he or she is over-using certain words. The first step is to change the case of all the letters in our input file to one case. "The" and "the" are the same word when doing counting. $ tr '[A-Z]' '[a-z]' < whats.gnu | ... The next step is to get rid of punctuation. Quoted words and unquoted words should be treated identically; it's easiest to just get the punctuation out of the way. $ tr '[A-Z]' '[a-z]' < whats.gnu | tr -cd '[A-Za-z0-9_ \012]' | ... The second `tr' command operates on the complement of the listed characters, which are all the letters, the digits, the underscore, and the blank. The `\012' represents the newline character; it has to be left alone. (The ASCII tab character should also be included for good measure in a production script.) At this point, we have data consisting of words separated by blank space. The words only contain alphanumeric characters (and the underscore). The next step is break the data apart so that we have one word per line. This makes the counting operation much easier, as we will see shortly. $ tr '[A-Z]' '[a-z]' < whats.gnu | tr -cd '[A-Za-z0-9_ \012]' | > tr -s '[ ]' '\012' | ... This command turns blanks into newlines. The `-s' option squeezes multiple newline characters in the output into just one. This helps us avoid blank lines. (The `>' is the shell's "secondary prompt." This is what the shell prints when it notices you haven't finished typing in all of a command.) We now have data consisting of one word per line, no punctuation, all one case. We're ready to count each word: $ tr '[A-Z]' '[a-z]' < whats.gnu | tr -cd '[A-Za-z0-9_ \012]' | > tr -s '[ ]' '\012' | sort | uniq -c | ... At this point, the data might look something like this: 60 a 2 able 6 about 1 above 2 accomplish 1 acquire 1 actually 2 additional The output is sorted by word, not by count! What we want is the most frequently used words first. Fortunately, this is easy to accomplish, with the help of two more `sort' options: `-n' do a numeric sort, not a textual one `-r' reverse the order of the sort The final pipeline looks like this: $ tr '[A-Z]' '[a-z]' < whats.gnu | tr -cd '[A-Za-z0-9_ \012]' | > tr -s '[ ]' '\012' | sort | uniq -c | sort -nr 156 the 60 a 58 to 51 of 51 and ... Whew! That's a lot to digest. Yet, the same principles apply. With six commands, on two lines (really one long one split for convenience), we've created a program that does something interesting and useful, in much less time than we could have written a C program to do the same thing. A minor modification to the above pipeline can give us a simple spelling checker! To determine if you've spelled a word correctly, all you have to do is look it up in a dictionary. If it is not there, then chances are that your spelling is incorrect. So, we need a dictionary. If you have the Slackware Linux distribution, you have the file `/usr/lib/ispell/ispell.words', which is a sorted, 38,400 word dictionary. Now, how to compare our file with the dictionary? As before, we generate a sorted list of words, one per line: $ tr '[A-Z]' '[a-z]' < whats.gnu | tr -cd '[A-Za-z0-9_ \012]' | > tr -s '[ ]' '\012' | sort -u | ... Now, all we need is a list of words that are _not_ in the dictionary. Here is where the `comm' command comes in. $ tr '[A-Z]' '[a-z]' < whats.gnu | tr -cd '[A-Za-z0-9_ \012]' | > tr -s '[ ]' '\012' | sort -u | > comm -23 - /usr/lib/ispell/ispell.words The `-2' and `-3' options eliminate lines that are only in the dictionary (the second file), and lines that are in both files. Lines only in the first file (standard input, our stream of words), are words that are not in the dictionary. These are likely candidates for spelling errors. This pipeline was the first cut at a production spelling checker on Unix. There are some other tools that deserve brief mention. `grep' search files for text that matches a regular expression `egrep' like `grep', but with more powerful regular expressions `wc' count lines, words, characters `tee' a T-fitting for data pipes, copies data to files and to standard output `sed' the stream editor, an advanced tool `awk' a data manipulation language, another advanced tool The software tools philosophy also espoused the following bit of advice: "Let someone else do the hard part." This means, take something that gives you most of what you need, and then massage it the rest of the way until it's in the form that you want. To summarize: 1. Each program should do one thing well. No more, no less. 2. Combining programs with appropriate plumbing leads to results where the whole is greater than the sum of the parts. It also leads to novel uses of programs that the authors might never have imagined. 3. Programs should never print extraneous header or trailer data, since these could get sent on down a pipeline. (A point we didn't mention earlier.) 4. Let someone else do the hard part. 5. Know your toolbox! Use each program appropriately. If you don't have an appropriate tool, build one. As of this writing, all the programs we've discussed are available via anonymous `ftp' from `prep.ai.mit.edu' as `/pub/gnu/textutils-1.9.tar.gz'.(1) None of what I have presented in this column is new. The Software Tools philosophy was first introduced in the book `Software Tools', by Brian Kernighan and P.J. Plauger (Addison-Wesley, ISBN 0-201-03669-X). This book showed how to write and use software tools. It was written in 1976, using a preprocessor for FORTRAN named `ratfor' (RATional FORtran). At the time, C was not as ubiquitous as it is now; FORTRAN was. The last chapter presented a `ratfor' to FORTRAN processor, written in `ratfor'. `ratfor' looks an awful lot like C; if you know C, you won't have any problem following the code. In 1981, the book was updated and made available as `Software Tools in Pascal' (Addison-Wesley, ISBN 0-201-10342-7). Both books remain in print, and are well worth reading if you're a programmer. They certainly made a major change in how I view programming. Initially, the programs in both books were available (on 9-track tape) from Addison-Wesley. Unfortunately, this is no longer the case, although you might be able to find copies floating around the Internet. For a number of years, there was an active Software Tools Users Group, whose members had ported the original `ratfor' programs to essentially every computer system with a FORTRAN compiler. The popularity of the group waned in the middle '80s as Unix began to spread beyond universities. With the current proliferation of GNU code and other clones of Unix programs, these programs now receive little attention; modern C versions are much more efficient and do more than these programs do. Nevertheless, as exposition of good programming style, and evangelism for a still-valuable philosophy, these books are unparalleled, and I recommend them highly. Acknowledgment: I would like to express my gratitude to Brian Kernighan of Bell Labs, the original Software Toolsmith, for reviewing this column. ---------- Footnotes ---------- (1) Version 1.9 was current when this column was written. Check the nearest GNU archive for the current version. The main GNU FTP site is now `ftp.gnu.org'. Index ***** +COUNT: See ```tail': Output the last part of files''. +FIRST_PAGE[:LAST_PAGE]: See ```pr': Paginate or columnate files for printing''. +N: See ```uniq': Uniquify files''. --across: See ```pr': Paginate or columnate files for printing''. --address-radix: See ```od': Write files in octal or other formats''. --all: See ```unexpand': Convert spaces to tabs''. --all-repeated: See ```uniq': Uniquify files''. --before: See ```tac': Concatenate and write files in reverse''. --binary <1>: See ```md5sum': Print or check message-digests''. --binary: See ```cat': Concatenate and write files''. --body-numbering: See ```nl': Number lines and write files''. --bytes <1>: See ```cut': Print selected parts of lines''. --bytes <2>: See ```wc': Print byte, word, and line counts''. --bytes <3>: See ```split': Split a file into fixed-size pieces''. --bytes <4>: See ```tail': Output the last part of files''. --bytes <5>: See ```head': Output the first part of files''. --bytes: See ```fold': Wrap input lines to fit in specified width''. --characters: See ```cut': Print selected parts of lines''. --chars: See ```wc': Print byte, word, and line counts''. --check-chars: See ```uniq': Uniquify files''. --columns: See ```pr': Paginate or columnate files for printing''. --count: See ```uniq': Uniquify files''. --crown-margin: See ```fmt': Reformat paragraph text''. --delimiter: See ```cut': Print selected parts of lines''. --delimiters: See ```paste': Merge lines of files''. --digits: See ```csplit': Split a file into context-determined pieces''. --double-space: See ```pr': Paginate or columnate files for printing''. --elide-empty-files: See ```csplit': Split a file into context-determined pieces''. --expand-tabs: See ```pr': Paginate or columnate files for printing''. --fields: See ```cut': Print selected parts of lines''. --first-line-number: See ```pr': Paginate or columnate files for printing''. --follow: See ```tail': Output the last part of files''. --footer-numbering: See ```nl': Number lines and write files''. --form-feed: See ```pr': Paginate or columnate files for printing''. --format: See ```od': Write files in octal or other formats''. --header: See ```pr': Paginate or columnate files for printing''. --header-numbering: See ```nl': Number lines and write files''. --help: See ``Common options''. --ignore-case <1>: See ```join': Join lines on a common field''. --ignore-case: See ```uniq': Uniquify files''. --indent: See ```pr': Paginate or columnate files for printing''. --initial: See ```expand': Convert tabs to spaces''. --join-blank-lines: See ```nl': Number lines and write files''. --join-lines: See ```pr': Paginate or columnate files for printing''. --keep-files: See ```csplit': Split a file into context-determined pieces''. --length: See ```pr': Paginate or columnate files for printing''. --line-bytes: See ```split': Split a file into fixed-size pieces''. --lines <1>: See ```wc': Print byte, word, and line counts''. --lines <2>: See ```split': Split a file into fixed-size pieces''. --lines <3>: See ```tail': Output the last part of files''. --lines: See ```head': Output the first part of files''. --max-consecutive-size-changes: See ```tail': Output the last part of files''. --max-line-length: See ```wc': Print byte, word, and line counts''. --max-unchanged-stats: See ```tail': Output the last part of files''. --merge: See ```pr': Paginate or columnate files for printing''. --no-file-warnings: See ```pr': Paginate or columnate files for printing''. --no-renumber: See ```nl': Number lines and write files''. --number: See ```cat': Concatenate and write files''. --number-format: See ```nl': Number lines and write files''. --number-lines: See ```pr': Paginate or columnate files for printing''. --number-nonblank: See ```cat': Concatenate and write files''. --number-separator: See ```nl': Number lines and write files''. --number-width: See ```nl': Number lines and write files''. --omit-header: See ```pr': Paginate or columnate files for printing''. --omit-pagination: See ```pr': Paginate or columnate files for printing''. --only-delimited: See ```cut': Print selected parts of lines''. --output-delimiter: See ```cut': Print selected parts of lines''. --output-duplicates: See ```od': Write files in octal or other formats''. --output-tabs: See ```pr': Paginate or columnate files for printing''. --page-increment: See ```nl': Number lines and write files''. --page_width: See ```pr': Paginate or columnate files for printing''. --pages: See ```pr': Paginate or columnate files for printing''. --pid: See ```tail': Output the last part of files''. --prefix: See ```csplit': Split a file into context-determined pieces''. --quiet <1>: See ```csplit': Split a file into context-determined pieces''. --quiet <2>: See ```tail': Output the last part of files''. --quiet: See ```head': Output the first part of files''. --read-bytes: See ```od': Write files in octal or other formats''. --regex: See ```tac': Concatenate and write files in reverse''. --repeated: See ```uniq': Uniquify files''. --retry: See ```tail': Output the last part of files''. --section-delimiter: See ```nl': Number lines and write files''. --sep-string: See ```pr': Paginate or columnate files for printing''. --separator <1>: See ```pr': Paginate or columnate files for printing''. --separator: See ```tac': Concatenate and write files in reverse''. --serial: See ```paste': Merge lines of files''. --show-all: See ```cat': Concatenate and write files''. --show-control-chars: See ```pr': Paginate or columnate files for printing''. --show-ends: See ```cat': Concatenate and write files''. --show-nonprinting <1>: See ```pr': Paginate or columnate files for printing''. --show-nonprinting: See ```cat': Concatenate and write files''. --show-tabs: See ```cat': Concatenate and write files''. --silent <1>: See ```csplit': Split a file into context-determined pieces''. --silent <2>: See ```tail': Output the last part of files''. --silent: See ```head': Output the first part of files''. --skip-bytes: See ```od': Write files in octal or other formats''. --skip-chars: See ```uniq': Uniquify files''. --skip-fields: See ```uniq': Uniquify files''. --sleep-interval: See ```tail': Output the last part of files''. --spaces: See ```fold': Wrap input lines to fit in specified width''. --split-only: See ```fmt': Reformat paragraph text''. --squeeze-blank: See ```cat': Concatenate and write files''. --starting-line-number: See ```nl': Number lines and write files''. --status: See ```md5sum': Print or check message-digests''. --strings: See ```od': Write files in octal or other formats''. --suffix: See ```csplit': Split a file into context-determined pieces''. --sysv: See ```sum': Print checksum and block counts''. --tabs <1>: See ```unexpand': Convert spaces to tabs''. --tabs: See ```expand': Convert tabs to spaces''. --tagged-paragraph: See ```fmt': Reformat paragraph text''. --text: See ```md5sum': Print or check message-digests''. --traditional: See ```od': Write files in octal or other formats''. --uniform-spacing: See ```fmt': Reformat paragraph text''. --unique: See ```uniq': Uniquify files''. --verbose <1>: See ```split': Split a file into fixed-size pieces''. --verbose <2>: See ```tail': Output the last part of files''. --verbose: See ```head': Output the first part of files''. --version: See ``Common options''. --warn: See ```md5sum': Print or check message-digests''. --width <1>: See ```fold': Wrap input lines to fit in specified width''. --width <2>: See ```pr': Paginate or columnate files for printing''. --width <3>: See ```fmt': Reformat paragraph text''. --width: See ```od': Write files in octal or other formats''. --words: See ```wc': Print byte, word, and line counts''. -1 <1>: See ```join': Join lines on a common field''. -1: See ```comm': Compare two sorted files line by line''. -2 <1>: See ```join': Join lines on a common field''. -2: See ```comm': Compare two sorted files line by line''. -3: See ```comm': Compare two sorted files line by line''. -a <1>: See ```unexpand': Convert spaces to tabs''. -a <2>: See ```join': Join lines on a common field''. -a <3>: See ```pr': Paginate or columnate files for printing''. -a: See ```od': Write files in octal or other formats''. -A <1>: See ```od': Write files in octal or other formats''. -A: See ```cat': Concatenate and write files''. -b <1>: See ```cut': Print selected parts of lines''. -b <2>: See ```sort': Sort text files''. -b <3>: See ```md5sum': Print or check message-digests''. -b <4>: See ```csplit': Split a file into context-determined pieces''. -b <5>: See ```split': Split a file into fixed-size pieces''. -b <6>: See ```fold': Wrap input lines to fit in specified width''. -b <7>: See ```od': Write files in octal or other formats''. -b <8>: See ```nl': Number lines and write files''. -b <9>: See ```tac': Concatenate and write files in reverse''. -b: See ```cat': Concatenate and write files''. -B: See ```cat': Concatenate and write files''. -c <1>: See ```cut': Print selected parts of lines''. -c <2>: See ```uniq': Uniquify files''. -c <3>: See ```sort': Sort text files''. -c: See ```wc': Print byte, word, and line counts''. -C: See ```split': Split a file into fixed-size pieces''. -c <1>: See ```tail': Output the last part of files''. -c <2>: See ```head': Output the first part of files''. -c <3>: See ```pr': Paginate or columnate files for printing''. -c <4>: See ```fmt': Reformat paragraph text''. -c: See ```od': Write files in octal or other formats''. -COLUMN: See ```pr': Paginate or columnate files for printing''. -COUNT <1>: See ```tail': Output the last part of files''. -COUNT: See ```head': Output the first part of files''. -d <1>: See ```paste': Merge lines of files''. -d: See ```cut': Print selected parts of lines''. -D: See ```uniq': Uniquify files''. -d <1>: See ```uniq': Uniquify files''. -d <2>: See ```sort': Sort text files''. -d <3>: See ```pr': Paginate or columnate files for printing''. -d <4>: See ```od': Write files in octal or other formats''. -d: See ```nl': Number lines and write files''. -e <1>: See ```join': Join lines on a common field''. -e: See ```pr': Paginate or columnate files for printing''. -E: See ```cat': Concatenate and write files''. -e: See ```cat': Concatenate and write files''. -f <1>: See ```cut': Print selected parts of lines''. -f <2>: See ```uniq': Uniquify files''. -f <3>: See ```sort': Sort text files''. -f <4>: See ```csplit': Split a file into context-determined pieces''. -f <5>: See ```tail': Output the last part of files''. -f: See ```pr': Paginate or columnate files for printing''. -F: See ```pr': Paginate or columnate files for printing''. -f <1>: See ```od': Write files in octal or other formats''. -f: See ```nl': Number lines and write files''. -g: See ```sort': Sort text files''. -h <1>: See ```pr': Paginate or columnate files for printing''. -h <2>: See ```od': Write files in octal or other formats''. -h: See ```nl': Number lines and write files''. -i <1>: See ```expand': Convert tabs to spaces''. -i <2>: See ```join': Join lines on a common field''. -i <3>: See ```uniq': Uniquify files''. -i <4>: See ```sort': Sort text files''. -i <5>: See ```pr': Paginate or columnate files for printing''. -i <6>: See ```od': Write files in octal or other formats''. -i: See ```nl': Number lines and write files''. -J: See ```pr': Paginate or columnate files for printing''. -j: See ```od': Write files in octal or other formats''. -j1: See ```join': Join lines on a common field''. -j2: See ```join': Join lines on a common field''. -k <1>: See ```sort': Sort text files''. -k: See ```csplit': Split a file into context-determined pieces''. -L: See ```wc': Print byte, word, and line counts''. -l <1>: See ```wc': Print byte, word, and line counts''. -l <2>: See ```split': Split a file into fixed-size pieces''. -l <3>: See ```pr': Paginate or columnate files for printing''. -l <4>: See ```od': Write files in octal or other formats''. -l: See ```nl': Number lines and write files''. -M: See ```sort': Sort text files''. -m <1>: See ```sort': Sort text files''. -m: See ```pr': Paginate or columnate files for printing''. -n: See ```cut': Print selected parts of lines''. -N: See ```uniq': Uniquify files''. -n <1>: See ```sort': Sort text files''. -n <2>: See ```csplit': Split a file into context-determined pieces''. -n <3>: See ```tail': Output the last part of files''. -n: See ```head': Output the first part of files''. -N: See ```pr': Paginate or columnate files for printing''. -n: See ```pr': Paginate or columnate files for printing''. -N: See ```od': Write files in octal or other formats''. -n <1>: See ```nl': Number lines and write files''. -n: See ```cat': Concatenate and write files''. -o <1>: See ```sort': Sort text files''. -o <2>: See ```pr': Paginate or columnate files for printing''. -o: See ```od': Write files in octal or other formats''. -p: See ```nl': Number lines and write files''. -q <1>: See ```csplit': Split a file into context-determined pieces''. -q <2>: See ```tail': Output the last part of files''. -q: See ```head': Output the first part of files''. -r <1>: See ```sort': Sort text files''. -r <2>: See ```sum': Print checksum and block counts''. -r <3>: See ```pr': Paginate or columnate files for printing''. -r: See ```tac': Concatenate and write files in reverse''. -s <1>: See ```paste': Merge lines of files''. -s <2>: See ```cut': Print selected parts of lines''. -s <3>: See ```uniq': Uniquify files''. -s <4>: See ```sum': Print checksum and block counts''. -s <5>: See ```csplit': Split a file into context-determined pieces''. -s: See ```fold': Wrap input lines to fit in specified width''. -S: See ```pr': Paginate or columnate files for printing''. -s <1>: See ```pr': Paginate or columnate files for printing''. -s <2>: See ```fmt': Reformat paragraph text''. -s <3>: See ```od': Write files in octal or other formats''. -s <4>: See ```nl': Number lines and write files''. -s <5>: See ```tac': Concatenate and write files in reverse''. -s: See ```cat': Concatenate and write files''. -t <1>: See ```unexpand': Convert spaces to tabs''. -t <2>: See ```expand': Convert tabs to spaces''. -t <3>: See ```sort': Sort text files''. -t: See ```md5sum': Print or check message-digests''. -T: See ```pr': Paginate or columnate files for printing''. -t <1>: See ```pr': Paginate or columnate files for printing''. -t <2>: See ```fmt': Reformat paragraph text''. -t: See ```od': Write files in octal or other formats''. -T: See ```cat': Concatenate and write files''. -t: See ```cat': Concatenate and write files''. -TAB <1>: See ```unexpand': Convert spaces to tabs''. -TAB: See ```expand': Convert tabs to spaces''. -u <1>: See ```uniq': Uniquify files''. -u <2>: See ```sort': Sort text files''. -u <3>: See ```fmt': Reformat paragraph text''. -u: See ```cat': Concatenate and write files''. -v <1>: See ```tail': Output the last part of files''. -v <2>: See ```head': Output the first part of files''. -v <3>: See ```pr': Paginate or columnate files for printing''. -v <4>: See ```od': Write files in octal or other formats''. -v <5>: See ```nl': Number lines and write files''. -v: See ```cat': Concatenate and write files''. -w <1>: See ```uniq': Uniquify files''. -w <2>: See ```md5sum': Print or check message-digests''. -w <3>: See ```wc': Print byte, word, and line counts''. -w: See ```fold': Wrap input lines to fit in specified width''. -W: See ```pr': Paginate or columnate files for printing''. -w <1>: See ```pr': Paginate or columnate files for printing''. -w <2>: See ```fmt': Reformat paragraph text''. -w <3>: See ```od': Write files in octal or other formats''. -w: See ```nl': Number lines and write files''. -WIDTH: See ```fmt': Reformat paragraph text''. -x: See ```od': Write files in octal or other formats''. -z <1>: See ```sort': Sort text files''. -z: See ```csplit': Split a file into context-determined pieces''. 128-bit checksum: See ```md5sum': Print or check message-digests''. 16-bit checksum: See ```sum': Print checksum and block counts''. across columns: See ```pr': Paginate or columnate files for printing''. all duplicate lines, outputting: See ```uniq': Uniquify files''. alnum: See ``Specifying sets of characters''. alpha: See ``Specifying sets of characters''. ASCII dump of files: See ```od': Write files in octal or other formats''. backslash escapes: See ``Specifying sets of characters''. binary and text I/O in cat: See ```cat': Concatenate and write files''. binary input files: See ```md5sum': Print or check message-digests''. blank: See ``Specifying sets of characters''. blank lines, numbering: See ```nl': Number lines and write files''. blanks, ignoring leading: See ```sort': Sort text files''. body, numbering: See ```nl': Number lines and write files''. BSD sum: See ```sum': Print checksum and block counts''. BSD tail: See ```tail': Output the last part of files''. bugs, reporting: See ``Introduction''. byte count: See ```wc': Print byte, word, and line counts''. case folding: See ```sort': Sort text files''. cat: See ```cat': Concatenate and write files''. characters classes: See ``Specifying sets of characters''. checking for sortedness: See ```sort': Sort text files''. checksum, 128-bit: See ```md5sum': Print or check message-digests''. checksum, 16-bit: See ```sum': Print checksum and block counts''. cksum: See ```cksum': Print CRC checksum and byte counts''. cntrl: See ``Specifying sets of characters''. comm: See ```comm': Compare two sorted files line by line''. common field, joining on: See ```join': Join lines on a common field''. common lines: See ```comm': Compare two sorted files line by line''. common options: See ``Common options''. comparing sorted files: See ```comm': Compare two sorted files line by line''. concatenate and write files: See ```cat': Concatenate and write files''. context splitting: See ```csplit': Split a file into context-determined pieces''. converting tabs to spaces: See ```expand': Convert tabs to spaces''. copying files: See ```cat': Concatenate and write files''. CRC checksum: See ```cksum': Print CRC checksum and byte counts''. crown margin: See ```fmt': Reformat paragraph text''. csplit: See ```csplit': Split a file into context-determined pieces''. cut: See ```cut': Print selected parts of lines''. cyclic redundancy check: See ```cksum': Print CRC checksum and byte counts''. deleting characters: See ``Squeezing repeats and deleting''. descriptor follow option: See ```tail': Output the last part of files''. differing lines: See ```comm': Compare two sorted files line by line''. digit: See ``Specifying sets of characters''. double spacing: See ```pr': Paginate or columnate files for printing''. down columns: See ```pr': Paginate or columnate files for printing''. duplicate lines, outputting: See ```uniq': Uniquify files''. empty lines, numbering: See ```nl': Number lines and write files''. entire files, output of: See ``Output of entire files''. equivalence classes: See ``Specifying sets of characters''. expand: See ```expand': Convert tabs to spaces''. field separator character: See ```sort': Sort text files''. file contents, dumping unambiguously: See ```od': Write files in octal or other formats''. file offset radix: See ```od': Write files in octal or other formats''. fingerprint, 128-bit: See ```md5sum': Print or check message-digests''. first part of files, outputting: See ```head': Output the first part of files''. fmt: See ```fmt': Reformat paragraph text''. fold: See ```fold': Wrap input lines to fit in specified width''. folding long input lines: See ```fold': Wrap input lines to fit in specified width''. footers, numbering: See ```nl': Number lines and write files''. formatting file contents: See ``Formatting file contents''. general numeric sort: See ```sort': Sort text files''. graph: See ``Specifying sets of characters''. growing files: See ```tail': Output the last part of files''. head: See ```head': Output the first part of files''. headers, numbering: See ```nl': Number lines and write files''. help, online: See ``Common options''. hex dump of files: See ```od': Write files in octal or other formats''. indenting lines: See ```pr': Paginate or columnate files for printing''. initial part of files, outputting: See ```head': Output the first part of files''. initial tabs, converting: See ```expand': Convert tabs to spaces''. input tabs: See ```pr': Paginate or columnate files for printing''. introduction: See ``Introduction''. join: See ```join': Join lines on a common field''. Knuth, Donald E.: See ```fmt': Reformat paragraph text''. last part of files, outputting: See ```tail': Output the last part of files''. LC_COLLATE <1>: See ```join': Join lines on a common field''. LC_COLLATE <2>: See ```comm': Compare two sorted files line by line''. LC_COLLATE: See ```sort': Sort text files''. LC_CTYPE: See ```sort': Sort text files''. LC_NUMERIC: See ```sort': Sort text files''. LC_TIME: See ```sort': Sort text files''. left margin: See ```pr': Paginate or columnate files for printing''. line count: See ```wc': Print byte, word, and line counts''. line numbering: See ```nl': Number lines and write files''. line-breaking: See ```fmt': Reformat paragraph text''. line-by-line comparison: See ```comm': Compare two sorted files line by line''. ln format for nl: See ```nl': Number lines and write files''. logical pages, numbering on: See ```nl': Number lines and write files''. lower: See ``Specifying sets of characters''. md5sum: See ```md5sum': Print or check message-digests''. merging files: See ```paste': Merge lines of files''. merging files in parallel: See ```pr': Paginate or columnate files for printing''. merging sorted files: See ```sort': Sort text files''. message-digest, 128-bit: See ```md5sum': Print or check message-digests''. months, sorting by: See ```sort': Sort text files''. multicolumn output, generating: See ```pr': Paginate or columnate files for printing''. name follow option: See ```tail': Output the last part of files''. nl: See ```nl': Number lines and write files''. numbering lines: See ```nl': Number lines and write files''. numeric sort: See ```sort': Sort text files''. octal dump of files: See ```od': Write files in octal or other formats''. od: See ```od': Write files in octal or other formats''. operating on characters: See ``Operating on characters''. operating on sorted files: See ``Operating on sorted files''. output file name prefix <1>: See ```csplit': Split a file into context-determined pieces''. output file name prefix: See ```split': Split a file into fixed-size pieces''. output file name suffix: See ```csplit': Split a file into context-determined pieces''. output of entire files: See ``Output of entire files''. output of parts of files: See ``Output of parts of files''. output tabs: See ```pr': Paginate or columnate files for printing''. overwriting of input, allowed: See ```sort': Sort text files''. paragraphs, reformatting: See ```fmt': Reformat paragraph text''. parts of files, output of: See ``Output of parts of files''. paste: See ```paste': Merge lines of files''. phone directory order: See ```sort': Sort text files''. pieces, splitting a file into: See ```split': Split a file into fixed-size pieces''. Plass, Michael F.: See ```fmt': Reformat paragraph text''. POSIX.2: See ``Introduction''. POSIXLY_CORRECT: See ``Warning messages''. pr: See ```pr': Paginate or columnate files for printing''. print: See ``Specifying sets of characters''. printing, preparing files for: See ```pr': Paginate or columnate files for printing''. ptx: See ```ptx': Produce permuted indexes''. punct: See ``Specifying sets of characters''. radix for file offsets: See ```od': Write files in octal or other formats''. ranges: See ``Specifying sets of characters''. reformatting paragraph text: See ```fmt': Reformat paragraph text''. repeated characters: See ``Specifying sets of characters''. reverse sorting: See ```sort': Sort text files''. reversing files: See ```tac': Concatenate and write files in reverse''. rn format for nl: See ```nl': Number lines and write files''. rz format for nl: See ```nl': Number lines and write files''. screen columns: See ```fold': Wrap input lines to fit in specified width''. section delimiters of pages: See ```nl': Number lines and write files''. sentences and line-breaking: See ```fmt': Reformat paragraph text''. sort: See ```sort': Sort text files''. sort field: See ```sort': Sort text files''. sort zero-terminated lines: See ```sort': Sort text files''. sorted files, operations on: See ``Operating on sorted files''. sorting files: See ```sort': Sort text files''. space: See ``Specifying sets of characters''. specifying sets of characters: See ``Specifying sets of characters''. split: See ```split': Split a file into fixed-size pieces''. splitting a file into pieces: See ```split': Split a file into fixed-size pieces''. splitting a file into pieces by context: See ```csplit': Split a file into context-determined pieces''. squeezing blank lines: See ```cat': Concatenate and write files''. squeezing repeat characters: See ``Squeezing repeats and deleting''. string constants, outputting: See ```od': Write files in octal or other formats''. sum: See ```sum': Print checksum and block counts''. summarizing files: See ``Summarizing files''. System V sum: See ```sum': Print checksum and block counts''. tabs to spaces, converting: See ```expand': Convert tabs to spaces''. tabstops, setting: See ```expand': Convert tabs to spaces''. tac: See ```tac': Concatenate and write files in reverse''. tagged paragraphs: See ```fmt': Reformat paragraph text''. tail: See ```tail': Output the last part of files''. telephone directory order: See ```sort': Sort text files''. text input files: See ```md5sum': Print or check message-digests''. text utilities: See ``GNU text utilities''. text, reformatting: See ```fmt': Reformat paragraph text''. TMPDIR: See ```sort': Sort text files''. topological sort: See ```tsort': Topological sort''. total counts: See ```wc': Print byte, word, and line counts''. tr: See ```tr': Translate, squeeze, and/or delete characters''. translating characters: See ``Translating''. tsort: See ```tsort': Topological sort''. type size: See ```od': Write files in octal or other formats''. unexpand: See ```unexpand': Convert spaces to tabs''. uniq: See ```uniq': Uniquify files''. unique lines, outputting: See ```uniq': Uniquify files''. uniquify files: See ```uniq': Uniquify files''. uniquifying output: See ```sort': Sort text files''. unprintable characters, ignoring: See ```sort': Sort text files''. upper: See ``Specifying sets of characters''. utilities for text handling: See ``GNU text utilities''. verifying MD5 checksums: See ```md5sum': Print or check message-digests''. version number, finding: See ``Common options''. wc: See ```wc': Print byte, word, and line counts''. word count: See ```wc': Print byte, word, and line counts''. wrapping long input lines: See ```fold': Wrap input lines to fit in specified width''. xdigit: See ``Specifying sets of characters''. Table of Contents ***************** GNU text utilities Introduction Common options Output of entire files `cat': Concatenate and write files `tac': Concatenate and write files in reverse `nl': Number lines and write files `od': Write files in octal or other formats Formatting file contents `fmt': Reformat paragraph text `pr': Paginate or columnate files for printing `fold': Wrap input lines to fit in specified width Output of parts of files `head': Output the first part of files `tail': Output the last part of files `split': Split a file into fixed-size pieces `csplit': Split a file into context-determined pieces Summarizing files `wc': Print byte, word, and line counts `sum': Print checksum and block counts `cksum': Print CRC checksum and byte counts `md5sum': Print or check message-digests Operating on sorted files `sort': Sort text files `uniq': Uniquify files `comm': Compare two sorted files line by line `tsort': Topological sort `ptx': Produce permuted indexes General options Charset selection Word selection and input processing Output formatting The GNU extensions to `ptx' Operating on fields within a line `cut': Print selected parts of lines `paste': Merge lines of files `join': Join lines on a common field Operating on characters `tr': Translate, squeeze, and/or delete characters Specifying sets of characters Translating Squeezing repeats and deleting Warning messages `expand': Convert tabs to spaces `unexpand': Convert spaces to tabs Opening the software toolbox Toolbox introduction I/O redirection The `who' command The `cut' command The `sort' command The `uniq' command Putting the tools together Index