This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

       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.

       Default.

       Default.

       Thefollowingsectionsareinformative.

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for  Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       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.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2017                                         TSORT(1POSIX)

       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.

       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 POSIX.1‐2017, Section8.2, InternationalizationVariables 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.

       The command:

           tsort <<EOF
           a b c c d e
           g g
           f g e f
           h h
           EOF

       produces the output:

           abcdefgh

       The following exit values shall be returned:

        0    Successful completion.

       >0    An error occurred.

       None.

       None.

       The input file shall be a text file.

       tsort — topological sort

       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.

       None.

       None.

       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.

       None.

       The Base Definitions volume of POSIX.1‐2017, Chapter8, EnvironmentVariables

       The standard error shall be used only for diagnostic messages.

       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.

       The standard output shall be a text file consisting of the order list produced from the partially ordered
       input.

       tsort [file]