tsort

Sort dependencies

$ tsort [dependencies.txt]

$ echo -e "a b\nb c" | tsort

$ tsort [makefile_deps]

tsort [file]

tsort performs topological sorting. It orders items respecting dependencies.
Input is pairs of items. First depends on second.
Output lists items in order. Dependencies come before dependents.
Cycles are reported as errors. Circular dependencies can't be sorted.
Common for build systems. Determine compilation order.

Items in dependency order: d, c, b, a

Detects cycles but can't resolve. Single dependency per line pair. Whitespace separated.

tsort is part of POSIX and has been in Unix since early versions. It was originally used for ordering object files in linker commands.

sort(1), make(1)