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SORT(1P)                   POSIX Programmer's Manual                  SORT(1P)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may dif-
       fer (consult the corresponding Linux manual page for details of Linux behavior), or the interface  may  not  be
       implemented on Linux.

NAME
       sort - sort, merge, or sequence check text files

SYNOPSIS
       sort [-m][-o output][-bdfinru][-t char][-k keydef]... [file...]

       sort -c [-bdfinru][-t char][-k keydef][file]


DESCRIPTION
       The sort utility shall perform one of the following functions:

        1. Sort lines of all the named files together and write the result to the specified output.


        2. Merge lines of all the named (presorted) files together and write the result to the specified output.


        3. Check that a single input file is correctly presorted.


       Comparisons  shall be based on one or more sort keys extracted from each line of input (or, if no sort keys are
       specified, the entire line up to, but not including, the terminating <newline>), and shall be  performed  using
       the collating sequence of the current locale.

OPTIONS
       The  sort  utility  shall conform to the Base Definitions volume of IEEE Std 1003.1-2001, Section 12.2, Utility
       Syntax Guidelines, and the -k keydef option should follow the -b, -d, -f, -i, -n, and -r options.

       The following options shall be supported:

       -c     Check that the single input file is ordered as specified by the arguments and the collating sequence  of
              the current locale. No output shall be produced; only the exit code shall be affected.

       -m     Merge only; the input file shall be assumed to be already sorted.

       -o  output
              Specify  the name of an output file to be used instead of the standard output. This file can be the same
              as one of the input files.

       -u     Unique: suppress all but one in each set of lines having equal keys.  If used with the -c option,  check
              that there are no lines with duplicate keys, in addition to checking that the input file is sorted.


       The  following  options  shall override the default ordering rules. When ordering options appear independent of
       any key field specifications, the requested field ordering rules shall be applied globally to  all  sort  keys.
       When  attached  to  a  specific key (see -k), the specified ordering options shall override all global ordering
       options for that key.

       -d     Specify that only <blank>s and alphanumeric characters, according to the current  setting  of  LC_CTYPE,
              shall  be  significant  in  comparisons. The behavior is undefined for a sort key to which -i or -n also
              applies.

       -f     Consider all lowercase characters that have uppercase equivalents, according to the current  setting  of
              LC_CTYPE,  to be the uppercase equivalent for the purposes of comparison.

       -i     Ignore all characters that are non-printable, according to the current setting of LC_CTYPE.

       -n     Restrict  the  sort  key  to  an initial numeric string, consisting of optional <blank>s, optional minus
              sign, and zero or more digits with an optional radix character and thousands separators (as  defined  in
              the  current  locale), which shall be sorted by arithmetic value. An empty digit string shall be treated
              as zero.  Leading zeros and signs on zeros shall not affect ordering.

       -r     Reverse the sense of comparisons.


       The treatment of field separators can be altered using the options:

       -b     Ignore leading <blank>s when determining the starting and ending positions of a restricted sort key.  If
              the -b option is specified before the first -k option, it shall be applied to all -k options. Otherwise,
              the -b option can be attached independently to each -k field_start  or  field_end  option-argument  (see
              below).

       -t  char
              Use  char as the field separator character; char shall not be considered to be part of a field (although
              it can be included in a  sort  key).  Each  occurrence  of  char  shall  be  significant  (for  example,
              <char><char>  delimits  an empty field). If -t is not specified, <blank>s shall be used as default field
              separators; each maximal non-empty sequence of <blank>s that follows a non- <blank>  shall  be  a  field
              separator.


       Sort keys can be specified using the options:

       -k  keydef
              The keydef argument is a restricted sort key field definition.  The format of this definition is:


              field_start[type][,field_end[type]]

       where  field_start  and  field_end  define  a  key  field restricted to a portion of the line (see the EXTENDED
       DESCRIPTION section), and type is a modifier from the list of characters 'b', 'd', 'f', 'i', 'n', 'r' . The 'b'
       modifier  shall  behave like the -b option, but shall apply only to the field_start or field_end to which it is
       attached.  The other modifiers shall behave like the corresponding options, but shall apply  only  to  the  key
       field  to  which  they  are  attached; they shall have this effect if specified with field_start, field_end, or
       both. If any modifier is attached to a field_start or to a field_end, no option shall apply to  either.  Imple-
       mentations shall support at least nine occurrences of the -k option, which shall be significant in command line
       order. If no -k option is specified, a default sort key of the entire line shall be used.

       When there are multiple key fields, later keys shall be compared only after all  earlier  keys  compare  equal.
       Except  when  the -u option is specified, lines that otherwise compare equal shall be ordered as if none of the
       options -d, -f, -i, -n, or -k were present (but with -r still in effect, if it  was  specified)  and  with  all
       bytes in the lines significant to the comparison. The order in which lines that still compare equal are written
       is unspecified.


OPERANDS
       The following operand shall be supported:

       file   A pathname of a file to be sorted, merged, or checked. If no file operands are specified, or if  a  file
              operand is '-', the standard input shall be used.


STDIN
       The standard input shall be used only if no file operands are specified, or if a file operand is '-' .  See the
       INPUT FILES section.

INPUT FILES
       The input files shall be text files, except that the sort utility shall add a <newline> to the end  of  a  file
       ending with an incomplete last line.

ENVIRONMENT VARIABLES
       The following environment variables shall affect the execution of sort:

       LANG   Provide  a  default  value  for the internationalization variables that are unset or null. (See the Base
              Definitions  volume  of  IEEE Std 1003.1-2001,  Section  8.2,  Internationalization  Variables  for  the
              precedence of internationalization variables used to determine the values of locale categories.)

       LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables.

       LC_COLLATE

              Determine the locale for ordering rules.

       LC_CTYPE
              Determine the locale for the interpretation of sequences of bytes of text data as characters (for  exam-
              ple,  single-byte  as opposed to multi-byte characters in arguments and input files) and the behavior of
              character classification for the -b, -d, -f, -i, and -n options.

       LC_MESSAGES
              Determine the locale that should be used to affect the format and contents of diagnostic messages  writ-
              ten to standard error.

       LC_NUMERIC

              Determine  the  locale  for  the  definition  of  the radix character and thousands separator for the -n
              option.

       NLSPATH
              Determine the location of message catalogs for the processing of LC_MESSAGES .


ASYNCHRONOUS EVENTS
       Default.

STDOUT
       Unless the -o or -c options are in effect, the standard output shall contain the sorted input.

STDERR
       The standard error shall be used for diagnostic messages. A warning message about correcting an incomplete last
       line of an input file may be generated, but need not affect the final exit status.

OUTPUT FILES
       If the -o option is in effect, the sorted input shall be written to the file output.

EXTENDED DESCRIPTION
       The notation:


              -k field_start[type][,field_end[type]]

       shall  define  a key field that begins at field_start and ends at field_end inclusive, unless field_start falls
       beyond the end of the line or after field_end, in which case the key field is empty. A missing field_end  shall
       mean the last character of the line.

       A field comprises a maximal sequence of non-separating characters and, in the absence of option -t, any preced-
       ing field separator.

       The field_start portion of the keydef option-argument shall have the form:


              field_number[.first_character]

       Fields and characters within fields shall be numbered starting with 1.  The  field_number  and  first_character
       pieces,  interpreted  as  positive  decimal integers, shall specify the first character to be used as part of a
       sort key. If .first_character is omitted, it shall refer to the first character of the field.

       The field_end portion of the keydef option-argument shall have the form:


              field_number[.last_character]

       The field_number shall be as described above for field_start.  The last_character piece, interpreted as a  non-
       negative  decimal integer, shall specify the last character to be used as part of the sort key. If last_charac-
       ter evaluates to zero or .last_character is omitted, it shall refer to the last character of the  field  speci-
       fied by field_number.

       If  the  -b  option  or b type modifier is in effect, characters within a field shall be counted from the first
       non- <blank> in the field. (This shall apply separately to first_character and last_character.)

EXIT STATUS
       The following exit values shall be returned:

        0     All input files were output successfully, or -c was specified and the input file was correctly sorted.

        1     Under the -c option, the file was not ordered as specified, or if the -c and -u options were both speci-
              fied, two input lines were found with equal keys.

       >1     An error occurred.


CONSEQUENCES OF ERRORS
       Default.

       The following sections are informative.

APPLICATION USAGE
       The  default  value  for  -t, <blank>, has different properties from, for example, -t "<space>". If a line con-
       tains:


              <space><space>foo

       the following treatment would occur with default separation as opposed to specifically selecting a <space>:

                                          Field   Default             -t "<space>"
                                          1       <space><space>foo   empty
                                          2       empty               empty
                                          3       empty               foo

       The leading field separator itself is included in a field when -t  is  not  used.  For  example,  this  command
       returns an exit status of zero, meaning the input was already sorted:


              sort -c -k 2 <<eof
              y<tab>b
              x<space>a
              eof

       (assuming  that  a  <tab>  precedes  the <space> in the current collating sequence). The field separator is not
       included in a field when it is explicitly set via -t. This is historical practice and allows usage such as:


              sort -t "|" -k 2n <<eof
              Atlanta|425022|Georgia
              Birmingham|284413|Alabama
              Columbia|100385|South Carolina
              eof

       where the second field can be correctly sorted numerically without regard to the non-numeric field separator.

       The wording in the OPTIONS section clarifies that the -b, -d, -f, -i, -n, and -r options have  to  come  before
       the  first  sort  key specified if they are intended to apply to all specified keys. The way it is described in
       this volume of IEEE Std 1003.1-2001 matches historical practice, not historical documentation. The results  are
       unspecified if these options are specified after a -k option.

       The  -f  option might not work as expected in locales where there is not a one-to-one mapping between an upper-
       case and a lowercase letter.

EXAMPLES
        1. The following command sorts the contents of infile with the second field as the sort key:


           sort -k 2,2 infile


        2. The following command sorts, in reverse order, the contents of infile1 and infile2, placing the  output  in
           outfile and using the second character of the second field as the sort key (assuming that the first charac-
           ter of the second field is the field separator):


           sort -r -o outfile -k 2.2,2.2 infile1 infile2


        3. The following command sorts the contents of infile1 and infile2 using the second non- <blank> of the second
           field as the sort key:


           sort -k 2.2b,2.2b infile1 infile2


        4. The  following command prints the System V password file (user database) sorted by the numeric user ID (the
           third colon-separated field):


           sort -t : -k 3,3n /etc/passwd


        5. The following command prints the lines of the already sorted file infile, suppressing all  but  one  occur-
           rence of lines having the same third field:


           sort -um -k 3.1,3.0 infile


RATIONALE
       Examples in some historical documentation state that options -um with one input file keep the first in each set
       of lines with equal keys. This behavior was deemed to be an implementation artifact and was not standardized.

       The -z option was omitted; it is not standard practice on most systems and is inconsistent with using  sort  to
       sort  several  files individually and then merge them together. The text concerning -z in historical documenta-
       tion appeared to require implementations to determine the proper buffer length during the sort phase of  opera-
       tion, but not during the merge.

       The  -y  option was omitted because of non-portability. The -M option, present in System V, was omitted because
       of non-portability in international usage.

       An undocumented -T option exists in some implementations. It is used to specify a  directory  for  intermediate
       files.   Implementations are encouraged to support the use of the TMPDIR environment variable instead of adding
       an option to support this functionality.

       The -k option was added to satisfy two objections. First, the zero-based counting used by sort is  not  consis-
       tent with other utility conventions. Second, it did not meet syntax guideline requirements.

       Historical  documentation  indicates  that  "setting  -n implies -b". The description of -n already states that
       optional leading <blank>s are tolerated in doing the comparison.  If -b is enabled, rather than implied, by -n,
       this  has  unusual  side  effects. When a character offset is used in a column of numbers (for example, to sort
       modulo 100), that offset is measured relative to the most significant digit, not to the column.  Based  upon  a
       recommendation from the author of the original sort utility, the -b implication has been omitted from this vol-
       ume of IEEE Std 1003.1-2001, and an application wishing to achieve the previously mentioned side effects has to
       code the -b flag explicitly.

FUTURE DIRECTIONS
       None.

SEE ALSO
       comm, join, uniq, the System Interfaces volume of IEEE Std 1003.1-2001, toupper()

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Stan-
       dard for  Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group  Base
       Specifications  Issue  6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc
       and The Open Group. In the event of any discrepancy between this version and the original  IEEE  and  The  Open
       Group  Standard,  the  original IEEE and The Open Group Standard is the referee document. The original Standard
       can be obtained online at http://www.opengroup.org/unix/online.html .



IEEE/The Open Group                  2003                             SORT(1P)