bashfunctiontestingscripting

Determine if a function exists in bash


Currently I'm doing some unit tests which are executed from bash. Unit tests are initialized, executed and cleaned up in a bash script. This script usualy contains an init(), execute() and cleanup() functions. But they are not mandatory. I'd like to test if they are or are not defined.

I did this previously by greping and seding the source, but it seemed wrong. Is there a more elegant way to do this?

Edit: The following sniplet works like a charm:

fn_exists()
{
    LC_ALL=C type $1 | grep -q 'shell function'
}

Solution

  • Like this: [[ $(type -t foo) == function ]] && echo "Foo exists"

    The built-in type command will tell you whether something is a function, built-in function, external command, or just not defined.

    Additional examples:

    $ LC_ALL=C type foo
    bash: type: foo: not found
    
    $ LC_ALL=C type ls
    ls is aliased to `ls --color=auto'
    
    $ which type
    
    $ LC_ALL=C type type
    type is a shell builtin
    
    $ LC_ALL=C type -t rvm
    function
    
    $ if [ -n "$(LC_ALL=C type -t rvm)" ] && [ "$(LC_ALL=C type -t rvm)" = function ]; then echo rvm is a function; else echo rvm is NOT a function; fi
    rvm is a function