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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 dif-
       fer (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 Variables for the prece-
              dence 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 exam-
              ple, 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  writ-
              ten 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 output 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, Stan-
       dard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base  Specifica-
       tions  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 Stan-
       dard,  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)