--- /dev/null
+.\" You may copy, distribute and modify under the terms of the LDP General
+.\" Public License as specified in the LICENSE file that comes with the
+.\" gnumaniak distribution
+.\"
+.\" The author kindly requests that no comments regarding the "better"
+.\" suitability or up-to-date notices of any info documentation alternative
+.\" is added without contacting him first.
+.\"
+.\" (C) 2002 Ragnar Hojland Espinosa <ragnar@ragnar-hojland.com>
+.\"
+.\" GNU sort man page
+.\" man pages are NOT obsolete!
+.\" <ragnar@ragnar-hojland.com>
+.TH SORT 1 "7 October 2002" "GNU textutils 2.1"
+.SH NAME
+\fBsort\fR \- sort text files
+.SH SYNOPSIS
+.B sort
+.RB [ \-cm ]
+.RB [ \-bdfginruzM ]
+.RB [ "\+\fIPOS1\fR[\fB\-\fIPOS2" ]
+.RB [ "\-o \fIOUTFILE" ]
+.RB [ "\-t \fISEPARATOR" ]
+.RB [ "\-k \fIPOS1\fR[\fB,\fIPOS2" ]
+.RB [ "\-K \fIPOS1\fR[\fB,\fIPOS2" ]
+.RB [ "\-S \fISIZE\fR" ]
+.RB [ "\-T \fITEMPDIR" ]
+.RB [ \-\-reverse ]
+.RI [ FILE... ]
+
+.BR sort " [" \-\-help "] [" \-\-version ]
+.SH DESCRIPTION
+.B sort
+sorts, merges, or compares all the lines from any given
+.IR FILE s.
+concatenating the result and writing it to standard output
+If
+.I FILE
+is omitted or if it is a
+.RB ` \- ',
+standard input is used for reading.
+
+GNU \fBsort\fR (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,
+\fBsort\fR silently supplies one.
+
+Upon any error, \fBsort\fR exits with a status of 2'.
+
+If the environment variable \fBTMPDIR\fR is set, \fBsort\fR uses its value
+as the directory for temporary files instead of `/tmp'. The `\fB\-T
+\fiTEMPDIR\fR' option in turn overrides the environment variable.
+
+A position in a sort field specified with the \fB\-k\fR or \fB+\fR option
+has the form \fIF\fB.\fIC\fR, where \fIF\fR is the number of the field to
+use and \fIC\fR is the number of the first character from the beginning of
+the field (for \fB+\fIPOS\fR) or from the end of the previous field (for
+\fB\-\fIPOS\fR). If the \fB.\fIC\fR is omitted, it is taken to be the first
+character in the field. If the \fB\-b\fR option was specified, the
+\fB.\fIC\fR part of a field specification is counted from the first nonblank
+character of the field (for \fB+\fIPOS\fR) or from the first nonblank
+character following the previous field (for \fB\-\fIPOS\fR).
+
+A sort key option may also have any of the output ordering options
+appended to it, in which case the global ordering options are not used
+for that particular field. The \fB\-b\fR option may be independently
+attached to either or both of the \fB+\fIPOS\fR and \fB\-\fIPOS\fR 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.
+.SH OPTIONS
+.SS Behaviour
+The default behaviour for \fBsort\fR is to sort. You may change this
+behaviour with:
+.TP
+.B \-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.
+.TP
+.B \-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.
+.PP
+A pair of lines is compared as follows: if any key fields have been
+specified, \fBsort\fR 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.
+
+If any of the global options `\fB\-bdfinrM\fR' are given but no key fields
+are specified, \fBsort\fR 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), \fNsort\fR compares the lines byte
+by byte in machine collating sequence instead of \fBLC_COLLATE\fR. The last
+resort comparison honors the \fB\-r\fR global option. The \fB\-s\fR
+(stable) option disables this last-resort comparison so that lines in which
+all fields compare equal are left in their original relative order.
+\fB\-s\fR has no effect if no fields or global options are specified.
+.SS Output Ordering Options
+The following options affect how \fBsort\fR orders 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.
+.TP
+.B \-b
+Ignore leading blanks when finding sort keys in each line.
+.TP
+.B \-d
+Sort in "phone directory" order: ignore all characters except
+letters, digits and blanks when sorting.
+.TP
+.B \-f
+Fold lowercase characters into the equivalent uppercase characters
+when sorting so that, for example, `b' and `B' sort as equal.
+.TP
+.B \-g
+Sort numerically using \fBstrtod\fR(3) to arrive at the numeric
+values. This allows floating point numbers to be specified in
+scientific notation, like `1.0e-34' and `10e100'. Use this option
+only if there is no alternative; it is much slower than \fB\-n\fR and
+numbers with too many significant digits will be compared as if
+they had been truncated. In addition, numbers outside the range
+of representable double precision floating point numbers are
+treated as if they were zeroes; overflows, underflows and conversion
+errors are not reported.
+.TP
+.B \-i
+Ignore unprintable characters.
+.TP
+.B \-n
+Sort numerically: the number begins each line; specifically, it
+consists of optional whitespace, an optional `-' sign, and zero or
+more digits, optionally followed by a decimal point and zero or
+more digits.
+.sp
+\fBsort \-n\fR uses what might be considered an unconventional method
+to compare strings representing floating point numbers. Rather than first
+converting each string to the C \fBdouble\fR type and then comparing those
+values, sort aligns the radix points 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 \fBdouble\fR 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 \fB\-g\fR.
+.TP
+.B \-r, \-\-reverse
+Reverse the result of comparison, so that lines with greater key
+values appear earlier in the output instead of later.
+.TP
+.B \-M
+An initial string, consisting of any amount of whitespace, followed
+by three letters abbreviating a month name, is folded to upper
+case and compared in the order `JAN' < `FEB' < ... < `DEC'.
+Invalid names compare low to valid names.
+.SS Other Options
+.TP
+.B +\fIPOS1\fR[\fB-\fIPOS2\fR]
+The obsolete, traditional option for specifying a sort field. The
+field consists of the line between \fIPOS1\fR and up to but \fBnot
+including\fR \fIPOS2\fR (or the end of the line if \fIPOS2\fR is omitted).
+Fields and character positions are numbered starting with 0.
+.TP
+.B \-k \fIPOS1\fR[\fB,\fIPOS2\fR]
+.B \-K \fIPOS1\fR[\fB,\fIPOS2\fR]
+The recommended, POSIX, option for specifying a sort field. The
+field consists of the line between \fIPOS1\fR and \fIPOS2\fR (or the end of
+the line, if \fIPOS2\fR is omitted), \fBinclusive\fR. Fields and character
+positions are numbered starting with 1.
+.TP
+.B \-o \fIOUTFILE
+Write output to OUTFILE instead of standard output. If \fIOUTFILE\fR is one
+of the input files, \fBsort\fR copies it to a temporary file before sorting
+and writing the output to \fIOUTFILE\fR
+.TP
+.B \-t \fISEPARATOR
+Use character \fISEPARATOR\fR 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', \fBsort\fR
+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.
+.TP
+.B \-u
+For the default case or the \fB\-m\fR option, only output the first of
+a sequence of lines that compare equal. For the \fB\-c\fR option,
+check that no pair of consecutive lines compares equal.
+.TP
+.B \-z
+Treat the input as a set of lines, each terminated by a <NUL>
+(zero byte character) instead of a <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)
+.TP
+.B -S \fISIZE\fB
+Use a buffer of \fISIZE\fB KB. Different units may be specified by
+specifying multiplier suffix (see below).
+.TP
+.B \-T \fITEMPDIR
+Use \fITEMPDIR\fR as the directory for temporary files. This option
+overrides the \fBTMPDIR\fR environment variable. If multiple \fB\-T\fR
+options are specified, each directory is used and may improve performance on
+huge sorts/merges.
+.TP
+.B \-\-help
+Print a usage message on standard output and exit successfully.
+.TP
+.B \-\-version
+Print version information on standard output then exit successfully.
+.SH EXAMPLES
+\fB\(bu\fR Sort in descending (reverse) numeric order.
+.sp
+.RS
+.nf
+sort \-nr
+.fi
+.RE
+.sp
+\fB\(bu\fR 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.
+.sp
+.RS
+.nf
+sort \-k3
+.fi
+.RE
+.sp
+\fB\(bu\fR 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.
+.sp
+.RS
+.nf
+sort \-t : -k 2,2n \-k 5.3,5.4
+.fi
+.RE
+.sp
+Note that if you had written `\-k 2' instead of `-k 2,2' \fBsort\fR
+would have used all characters beginning in the second field and extending
+to the end of the line as the primary \fBnumeric\fR 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 \fBfield\fR, regardless of whether the modifier
+character is attached to the field-start and/or the field-end part
+of the key specifier.
+
+\fB\(bu\fR 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.
+.sp
+.RS
+.nf
+sort \-t : \-k 5b,5 \-k 3,3n /etc/passwd
+.fi
+.RE
+.sp
+An alternative is to use the global numeric modifier \fB\-n\fR.
+.sp
+.RS
+.nf
+sort \-t : \-n \-k 5b,5 \-k 3,3 /etc/passwd
+.fi
+.RE
+.sp
+\fB\(bu\fR Generate a tags file in case insensitive sorted order.
+.sp
+.RS
+.nf
+find src \-type f \-print0 | sort \-t / \-z \-f |
+xargs \-0 etags \-\-append
+.fi
+.RE
+.sp
+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,
+.sp
+.RS
+.nf
+sort \-t : \-n \-k 5b,5b \-k 3,3 /etc/passwd
+.fi
+.RE
+.sp
+or by using the global \fB\-b\fR modifier instead of \fB\-n\fR and an
+explicit `n' with the second key specifier.
+.sp
+.RS
+.nf
+sort \-t : -b \-k 5,5 \-k 3,3n /etc/passwd
+.fi
+.RE
+.SH MULTIPLIERS
+Numbers may be followed by a size letter to specify a multiple of that
+size, and a \fBB\fR to select normal bytes or a \fBD\fR to select
+decimal "commercial" bytes. For example `1KB' is equal to `1024' and
+`1KD' is equal to `1000'. Exceptions are \fBb\fR (512 bytes), \fBc\fR (1
+byte), and \fBw\fR (which should never be used - it means 2 in System V and
+4 in 4.2BSD), which can't be followed by a \fBB\fR or \fBD\fR.
+.TP
+.B k
+kilo: 2^10 = 1024 for normal bytes, or 10^3 = 1000 for decimal bytes
+.TP
+.B M
+Mega: 2^20 = 1,048,576 or 10^6 = 1,000,000
+.TP
+.B G
+Giga: 2^30 = 1,073,741,824 or 10^9 = 1,000,000,000
+.TP
+.B T
+Tera: 2^40 = 1,099,511,627,776 or 10^12 = 1,000,000,000,000
+.TP
+.B P
+Peta: 2^50 = 1,125,899,906,842,624 or 10^15 = 1,000,000,000,000,000
+.TP
+.B E
+Exa: 2^60 = 1,152,921,504,606,846,976 or 10^18 = 1,000,000,000,000,000,000
+.TP
+.B Z
+Zetta: 2^70 = 1,180,591,620,717,411,303,424 or 10^21 =
+1,000,000,000,000,000,000,000
+.TP
+.B Y
+Yotta: 2^80 = 1,208,925,819,614,629,174,706,176 or 10^24 =
+1,000,000,000,000,000,000,000,000
+.SH COMPATIBILITY
+Historical (BSD and System V) implementations of \fBsort\fR have
+differed in their interpretation of some options, particularly
+.BR \-b ", " \-f ", and " \-n .
+GNU sort follows the POSIX behavior, which is usually (but not always!) like
+the System V behavior. According to POSIX, \fB\-n\fR no longer implies
+\fB-b\fR. For consistency, \fB\-M\fR 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 \fB\-b\fR.
+.SH LOCALES
+.TP
+.B LC_COLLATE
+Specifies the character collating sequence used to realize all
+comparisions, unless specified otherwise.
+.TP
+.B LC_CTYPE
+Modifies the behaviour of the
+.BR \-b ", " \-d ", " \-f " and "\-i
+output ordering options.
+.TP
+.B LC_NUMERIC
+Specifies the radix character as well as the thousands separator.
+.TP
+.B LC_TIME
+Determines the month spellings, affecting \fB\-M\fR.
+.SH NOTES
+Report bugs to bug-textutils@gnu.org.
+.br
+Man page by Ragnar Hojland Espinosa <ragnar@ragnar-hojland.com>
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