Listing defined functions in Bash

Question

I'm trying to write some code in bash which uses introspection to select the appropriate function to call.

Determining the candidates requires knowing which functions are defined. It's easy to list defined variables in bash using only parameter expansion:

$ prefix_foo="one"
$ prefix_bar="two"
$ echo "${!prefix_*}"
prefix_bar prefix_foo

However, doing this for functions appears to require filtering the output of set -- a much more haphazard approach.

Is there a Right Way?

Answer 1

How about compgen:

compgen -A function   # compgen is a shell builtin

Answer 2

$ declare -F
declare -f ::
declare -f _get_longopts
declare -f _longopts_func
declare -f _onexit
...

So, Jed Daniel's alias,

declare -F | cut -d" " -f3

cuts on a space and echos the 3rd field:

$ declare -F | cut -d" " -f3
::
_get_longopts
_longopts_func
_onexit

Answer 3

I have an entry in my .bashrc that says:

alias list='declare -F |cut -d" " -f3'

Which allows me to type list and get a list of functions. When I added it, I probably understood what was happening, but I can't remember to save my life at the moment.

Good luck,

--jed

Answer 4

Use the declare builtin to list currently defined functions:

declare -F

Answer 5

zsh only (not what was asked for, but all the more generic questions have been closed as a duplicate of this):

typeset -f +

From man zshbuiltins:

-f     The  names  refer  to functions rather than parameters.
 +     If `+' appears by itself in a separate word as the last
       option, then the names of all parameters (functions with -f)
       are printed, but  the values  (function  bodies)  are not.

Example:

martin@martin ~ % cat test.zsh 
#!/bin/zsh

foobar()
{
  echo foobar
}

barfoo()
{
  echo barfoo
}

typeset -f +

Output:

martin@martin ~ % ./test.zsh
barfoo
foobar

Answer 6

This has no issues with IFS nor globbing:

readarray -t funcs < <(declare -F)

printf '%s\n' "${funcs[@]##* }"

Of course, that needs bash 4.0.

For bash since 2.04 use (a little trickier but equivalent):

IFS=$'\n' read -d '' -a funcs < <(declare -F)

If you need that the exit code of this option is zero, use this:

IFS=$'\n' read -d '' -a funcs < <( declare -F && printf '\0' )

It will exit unsuccesful (not 0) if either declare or read fail. (Thanks to @CharlesDuffy)

Answer 7

This collects a list of function names matching any of a list of patterns:

functions=$(for c in $patterns; do compgen -A function | grep "^$c\$")

The grep limits the output to only exact matches for the patterns.

Check out the bash command type as a better alternative to the following. Thanks to Charles Duffy for the clue.

The following uses that to answer the title question for humans rather than shell scripts: it adds a list of function names matching the given patterns, to the regular which list of shell scripts, to answer, "What code runs when I type a command?"

which() {
  for c in "$@"; do
    compgen -A function |grep "^$c\$" | while read line; do
      echo "shell function $line" 1>&2
     done
    /usr/bin/which "$c"
   done
 }

So,

(xkcd)Sandy$ which deactivate
shell function deactivate
(xkcd)Sandy$ which ls
/bin/ls
(xkcd)Sandy$ which .\*run_hook
shell function virtualenvwrapper_run_hook

This is arguably a violation of the Unix "do one thing" philosophy, but I've more than once been desperate because which wasn't finding a command that some package was supposed to contain, me forgetting about shell functions, so I've put this in my .profile.

Answer 8

#!/bin/bash
# list-defined-functions.sh
# Lists functions defined in this script.
# 
# Using `compgen -A function`,
# We can save the list of functions defined before running out script,
# the compare that to a new list at the end,
# resulting in the list of newly added functions.
# 
# Usage:
#   bash list-defined-functions.sh      # Run in new shell with no predefined functions
#   list-defined-functions.sh           # Run in current shell with plenty of predefined functions
#

# Example predefined function
foo() { echo 'y'; }

# Retain original function list
# If this script is run a second time, keep the list from last time
[[ $original_function_list ]] || original_function_list=$(compgen -A function)

# Create some new functions...
myfunc() { echo "myfunc is the best func"; }
function another_func() { echo "another_func is better"; }
function superfunction { echo "hey another way to define functions"; }
# ...

# function goo() { echo ok; }

[[ $new_function_list ]] || new_function_list=$(comm -13 \
    <(echo $original_function_list) \
    <(compgen -A function))

echo "Original functions were:"
echo "$original_function_list"
echo 
echo "New Functions defined in this script:"
echo "$new_function_list"

Answer 9

One (ugly) approach is to grep through the output of set:

set \
  | egrep '^[^[:space:]]+ [(][)][[:space:]]*$' \
  | sed -r -e 's/ [(][)][[:space:]]*$//'

Better approaches would be welcome.

Answer 10

Pure Bash:

saveIFS="$IFS"
IFS=$'\n'
funcs=($(declare -F))      # create an array
IFS="$saveIFS"
funcs=(${funcs[@]##* })    # keep only what's after the last space

Then, run at the Bash prompt as an example displaying bash-completion functions:

$ for i in ${funcs[@]}; do echo "$i"; done
__ack_filedir
__gvfs_multiple_uris
_a2dismod
. . .
$ echo ${funcs[42]}
_command