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> There's no good way of telling if a builtin exists programatically (for, let's say, feature detection). Doesn’t the `type` command (technically a builtin) me
by supriyo-biswas 2y ago
> There's no good way of telling if a builtin exists programatically (for, let's say, feature detection).
Doesn’t the `type` command (technically a builtin) meet your requirements?
- alganet 2y agoIt kinda does, and it is portable enough (modern bash zsh ksh dash busybox), thanks! Of the mainstream packaged shells, it fails only on `posh`, but that's fine, posh is super austere, it also lacks `command`. However, I will probably still use `command -v` for sporadic uses. That's because I don't need a subshell to capture the output: OLDPATH=$PATH;PATH= if command -v echo then echo is builtin fi PATH=$OLDPATH if test "$(type echo)" = "echo is a shell builtin" then echo is a builtin fi `type` however seems to be able to pick up more stuff, so I might use it some cases like this: case $(type echo) in 'echo is a shell builtin') do_something;; 'echo is aliased'*) do_something_else;; 'echo is /'*) do_something_else_entirely;; esac It kinda fits an early feature detection that I could put in a more sensible place (my lib init) and pay the subshell cost only once.