3 ms·

Type `help` in your shell to see a list of all the builtins.

by kesor 2y ago

alganet 2y ago
In _some_ shells! (most user shells anyway). `dash` for example does not have help. Some form of builtin list is always on the man pages though. There's no good way of telling if a builtin exists programatically (for, let's say, feature detection). There's an almost good way with `{ PATH=; command -v isthisreallife; }` and some shells will provide a `builtin isthisreallife` that you can use without having to nuke the PATH variable.
- 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 ago
    It 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.
- flaminHotSpeedo 2y ago
  I appreciate pedantry as much as the next person, but I think it's safe to say that if you're using a shell without support for `help` you can make your way without it. As a more practical suggestion, I find functionality detection is much less important since I learned to disavow all knowledge of a script when sharing it

Type `help` in your shell to see a list of all the builtins.

by kesor 2y ago

Type `help` in your shell to see a list of all the builtins.

In _some_ shells! (most user shells anyway). `dash` for example does not have help. Some form of builtin list is always on the man pages though. There's no good way of telling if a builtin exists programatically (for, let's say, feature detection). There's an almost good way with `{ PATH=; command -v isthisreallife; }` and some shells will provide a `builtin isthisreallife` that you can use without having to nuke the PATH variable.

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 ago
  It 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.
flaminHotSpeedo 2y ago
I appreciate pedantry as much as the next person, but I think it's safe to say that if you're using a shell without support for `help` you can make your way without it. As a more practical suggestion, I find functionality detection is much less important since I learned to disavow all knowledge of a script when sharing it