`tsort': Topological sort
=========================
`tsort' performs a topological sort on the given FILE, or standard
input if no input file is given or for a FILE of `-'. Synopsis:
tsort [OPTION] [FILE]
`tsort' reads its input as pairs of strings, separated by blanks,
indicating a partial ordering. The output is a total ordering that
corresponds to the given partial ordering.
For example
tsort <<EOF
a b c
d
e f
b c d e
EOF
will produce the output
a
b
c
d
e
f
`tsort' will detect cycles in the input and writes the first cycle
encountered to standard error.
Note that for a given partial ordering, generally there is no unique
total ordering.
The only options are `--help' and `--version'. Note:Common
options.