5. External Commands
cabal-install
provides a system for external commands, akin to the ones used by tools like git
or cargo
.
If you execute cabal <cmd>
, cabal-install
will search the path for an executable named cabal-<cmd>
and execute it. The name of the command is passed as the first argument and
the remaining arguments are passed afterwards. An error will be thrown in case the custom command is not found. The exit code of cabal when calling an external command is the same as the exit code
of the command.
The $CABAL
environment variable is set to the path of the cabal-install
executable
which invoked the subcommand.
It is strongly recommended that you implement your custom commands by calling the
CLI via the $CABAL
variable rather than linking against the Cabal
library.
There is no guarantee that the subcommand will link against the same version of the
Cabal
library as cabal-install
so it would lead to unexpected results and
incompatibilities.
cabal-install
can also display the help message of the external command.
When cabal help <cmd>
is invoked, then cabal-<cmd> <cmd> --help
will be called so
your external command can display a help message.
For ideas or existing external commands, visit this Discourse thread.