I make it a point of principle not to litter my entire codebase with hacks to accommodate stupid broken systems. If I must deal with them, I refactor the code so that their fix-ups are isolated.
If your shell is so old or broken that it doesn’t have command -v, firstly consider upgrading it.
Secondly, consider using shell functions to hide the brokenness.
if command -v sh >/dev/null 2>&1 ; then
# We're in a proper POSIX shell
i_need() {
command -v "$1" >/dev/null 2>&1 || {
echo "Can't find required subprogram $1 - aborting"
exit 1
}
}
else
# We're in busybox or some other broken shell
i_need() {
__can_do=$( which -- "$1" 2>&1 ) &&
case $__can_do in
*/"$1") : ;;
*) echo "Can't find required subprogram $1 - aborting"
exit 1
esac
}
fi
i_need cat
i_need id
i_need tar
i_need test
Not only does this avoid cluttering the whole program with variables, but the function name helps document the purpose of the checks.
Ok, sometimes you really do want the external program rather than the built-in.
Again, shell functions come to the rescue:
if (put your test here, to see if the built-in fubar is broken) ; then
fubar() {
command fubar "$@"
}
fi