Hacker News Reader

Comment by reacweb | Hacker News Reader

In bash, there is the build-in command named "command". I have used it for the same purpose, like in:

    command -v brew >/dev/null && brew install jq

View on HN

If you don't care for maximum POSIX compatibility, i.e. your script is bash-specific, it's better to use "hash", which is going to ignore aliases (but not functions) and also has the benefit of caching the command for further use.

  hash foo &>/dev/null || { echo "foo command not found blabla..." >&2; exit 1; }

more info: https://stackoverflow.com/questions/592620/how-to-check-if-a...

Wow. It's impossible to google, and on MacOS, `man command` is useless.

$ help command

command: command [-pVv] command [arg ...] Execute a simple command or display information about commands.

    Runs COMMAND with ARGS suppressing  shell function lookup, or display
    information about the specified COMMANDs.  Can be used to invoke commands
    on disk when a function with the same name exists.
    
    Options:
      -p    use a default value for PATH that is guaranteed to find all of
            the standard utilities
      -v    print a description of COMMAND similar to the `type' builtin
      -V    print a more verbose description of each COMMAND
    
    Exit Status:
    Returns exit status of COMMAND, or failure if COMMAND is not found.

Thank you.

I never knew about help to describe a builtin shell command. normally searching for something like "command" in the bash man page would be very tedious.

also: help echo

i do think 'man command' should bring up the specific man page for this, so there is no need to search into the bash man. this works with most builtin shell commands. e.g. 'man ls' is a thing

On (at least) Debian systems (, and probably many more) `ls` is not a built-in, but an external binary (`/usr/bin/ls`) is used.

`which ls` and `help ls` will show you, if it is similar on your system.

It does't need to be a built-in to have a man page (many first party and third party libraries come with their own man pages).

"man command" on linux says "no manual entry for command"

"man echo" on linux describes /usr/bin/echo "help echo" describes the builtin.

on the othe hand, "man command" on mac os x gives a huge manpage of builtins (still hard to search for the common word "command")

How little we expect from our computers. "help <command>" should be the first thing you expect to work.

`command` is a bash builtin, not an external program. The information is in the bash man page (which is hard to find in there because the word "command" is in the man page 7 bajillion times. Look in the major section "SHELL BUILTIN COMMANDS" where you find `cd` and others like it).

You can determine if something is a bash built-in by using 'which command'. If it's built-in, man won't work.

In config.fish I use type for this purpose, together with the exit code

  test (type brew 2>/dev/null); and brew # blahblah

type -p also works in bash/zsh

Fish as well, but the redirection of both stdout and stderr is different:

  type -p brew >/dev/null ^&1; and brew

in Bash it would be:

  type -p brew &>/dev/null && brew

Using test avoids caring about stdout/stderr.

Reply on news.ycombinator.com