tsort(1p) — Linux manual page
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
variables that are unset or null. (See the Base
Definitions volume of POSIX.1‐2017, Section 8.2,
Internationalization Variables 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 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
The Base Definitions volume of POSIX.1‐2017, Chapter 8,
Environment Variables
COPYRIGHT
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 .