TSORT(1) General Commands Manual TSORT(1)

tsort — topological sort

tsort [file]

The tsort utility writes to standard output a totally ordered list of items consistent with a partial ordering of items contained in the input.

The input consists of pairs of items (non-empty strings) separated by blanks. Pairs of different items indicate ordering. Pairs of identical items indicate presence, but not ordering.

None.

The following operand is supported:

file
A pathname of a text file to order. If no file operand is given, the standard input is used.

The standard input is 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 affect the execution of tsort :

Provide a default value for the internationalisation variables that are unset or null. If LANG is unset or null, the corresponding value from the implementation-dependent default locale will be used. If any of the internationalisation variables contains an invalid setting, the utility will behave as if none of the variables had been defined.
If set to a non-empty string value, override the values of all the other internationalisation variables.
Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single- as opposed to multi-byte characters in arguments and input files).
Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error.
Determine the location of message catalogues for the processing of LC_MESSAGES .

Default.

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

Used only for diagnostic messages.

None.

None.

The following exit values are returned:

Successful completion.
An error occurred.

Default.

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.

February 1997 posix.fail