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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> characters. 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 used if no file operand is  specified,  and
       shall  be used if the file operand is '-' and the implementation treats
       the '-' as meaning standard input.  Otherwise, the standard input shall
       not be used.  See the INPUT FILES section.
INPUT FILES
       The input file shall be a text file.
ENVIRONMENT VARIABLES
       The  following  environment  variables  shall  affect  the execution of
       tsort:
       LANG      Provide a default value for  the  internationalization  vari-
                 ables  that are unset or null. (See the Base Definitions vol-
                 ume of POSIX.1-2008, 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
       The Base Definitions volume of  POSIX.1-2008,  Chapter  8,  Environment
       Variables
COPYRIGHT
       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
       cal  and  Electronics  Engineers,  Inc  and  The  Open Group.  (This is
       POSIX.1-2008 with the 2013 Technical Corrigendum  1  applied.)  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.unix.org/online.html .
       Any typographical or formatting errors that appear  in  this  page  are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors,  see  https://www.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                            TSORT(1P)