tsort(P)                                               tsort(P)





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 internationaliza-
              tion  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 cate-
              gories.)

       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 mes-
              sages 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 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 Operat-
       ing System Interface (POSIX), The Open Group Base Speci-
       fications Issue 6, Copyright (C) 2001-2003 by the Insti-
       tute 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 .



POSIX                         2003                     tsort(P)
