Table of Contents
tsort - topological sort
tsort [file]
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.
None.
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.
The standard input shall be a text file that is used if no
file operand is given.
The input file named by the file operand
is a text file.
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 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 .
Default.
The standard
output shall be a text file consisting of the order list produced from
the partially ordered input.
The standard error shall be used only
for diagnostic messages.
None.
None.
The following exit values shall be returned:
- 0
- Successful completion.
- >0
- An error occurred.
Default.
The following sections
are informative.
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.
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
None.
None.
None.
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, 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 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
.
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