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

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
NAME
       tsort - topological sort
SYNOPSIS
       tsort [file]
DESCRIPTION
       The tsort utility shall write to standard output a totally ordered list
       of  items  consistent with a partial ordering of items contained in the
       input.
       The application shall ensure that the input consists of pairs of  items
       (non-empty  strings)  separated  by  <blank>s. Pairs of different items
       indicate ordering. Pairs of identical items indicate presence, but  not
       ordering.
OPTIONS
       None.
OPERANDS
       The following operand shall be supported:
       file   A pathname of a text file to order. If no file operand is given,
              the standard input shall be used.

STDIN
       The standard input shall be a text file that is used if no file operand
       is given.
INPUT FILES
       The input file named by the file operand is a text file.
ENVIRONMENT VARIABLES
       The  following  environment  variables  shall  affect  the execution of
       tsort:
       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  Vari-
              ables  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_CTYPE
              Determine  the  locale  for  the  interpretation of sequences of
              bytes of text data as characters (for  example,  single-byte  as
              opposed to multi-byte characters in arguments and input files).
       LC_MESSAGES
              Determine  the  locale  that should be used to affect the format
              and contents of diagnostic messages written to standard error.
       NLSPATH
              Determine the location of message catalogs for the processing of
              LC_MESSAGES .

ASYNCHRONOUS EVENTS
       Default.
STDOUT
       The  standard  output shall be a text file consisting of the order list
       produced from the partially ordered input.
STDERR
       The standard error shall be used only for diagnostic messages.
OUTPUT FILES
       None.
EXTENDED DESCRIPTION
       None.
EXIT STATUS
       The following exit values shall be returned:
        0     Successful completion.
       >0     An error occurred.

CONSEQUENCES OF ERRORS
       Default.
       The following sections are informative.
APPLICATION USAGE
       The LC_COLLATE variable need not affect the actions of tsort.  The out-
       put  ordering  is  not lexicographic, but depends on the pairs of items
       given as input.
EXAMPLES
       The command:

              tsort <<EOF
              a b c c d e
              g g
              f g e f
              h h
              EOF
       produces the output:

              a
              b
              c
              d
              e
              f
              g
              h
RATIONALE
       None.
FUTURE DIRECTIONS
       None.
SEE ALSO
       None.
COPYRIGHT
       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2003 Edition, Standard 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                            TSORT(1P)