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 (con-
       sult 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 precedence  of  international-
              ization 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 stan-
              dard 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,  Standard  for
       Information  Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                     TSORT(1P)