compgen: An Awesome Command To List All Linux Commands

last updated in Categories Command Line Hacks

Ever want to list all the Linux commands (including bash shell aliases and functions) you could run on the server / workstation? Look now further. Try compgen command.

compgen is bash built-in command and it will show all available commands, aliases, and functions for you. The syntax is:

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compgen option

compgen command examples

To list all the commands available to you, enter:

compgen -c

Sample outputs:

ls
if
then
else
elif
fi
....
mahjongg
sol
gtali
sl-h
gnobots2
gnotravex
iagno
fortune
gnect
gnome-sudoku
LS
glchess
gnuchess
gnuchessx

You can search or count the commands:

compgen -c | grep find
compgen -c | wc -l
echo "$USER user can run $(compgen -c | wc -l) commands on $HOSTNAME."

Sample outputs:

vivek user can run 3436 commands on wks01.

To list all the bash shell aliases available to you, enter:

compgen -a

Sample outputs:

..
...
....
.....
.4
.5
bc
cd..
chgrp
chmod
chown
cp
dnstop
egrep
ethtool
fastping
fgrep
grep
iftop
l.
ll
ln
ls
mcdflush
mcdshow
mcdstats
mount
mv
pscpu
pscpu10
psmem
psmem10
rm
tcpdump
update
updatey
vnstat
wget
which

See 30 awesome handy bash aliases for more information. Other options are as follows:

########################################
# Task: show all the bash built-ins
########################################
compgen -b
########################################
# Task: show all the bash keywords
########################################
compgen -k
########################################
# Task: show all the bash functions
########################################
compgen -A function

Putting it all together:

compgen  -abckA function
 
##  It doesnt get much better than this
compgen  -abckA function | less
compgen  -abckA function | grep -i --color searchStringHere

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Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin, DevOps engineer, and a trainer for the Linux operating system/Unix shell scripting. Get the latest tutorials on SysAdmin, Linux/Unix and open source topics via RSS/XML feed or weekly email newsletter.


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10 comment

  9. Here’s a pointless script! If you have `whatis` enabled, you can run this script to tell you what each command is (when that info is available, of course):

    #!/bin/bash

commands=`compgen -c`
let count=1

for i in ${commands[@]}
do

        what=`whatis $i`

        echo -e "n33[38;5;148m$count. $i: 33[39m"
        echo -e "$what"

        ((count++))


done

    Last edited by Admin: pre tags added.

    Reply

    1. Curtis, FYI when you used commands=`compgen -c`, it loaded commands with a string (albeit a very long one). So in this instance, you could have used:

      for i in $commands

      The ${commands[@]} format is generally reserved for use with arrays. It worked in this instance but is not a good habit. If the output contained spaces the aforementioned would fail. You’d probably want to do this:

      Load output of compgen into an array named commands (the -t options strips trailing newline)

      readarray -t commands < <(compgen -c)

      Note the quotes to prevent word splitting. The for loop will then run through ${commands[0]}, ${commands[1]}, ${commands[2]}, etc…

      for i in "${commands[@]}"

      In my endless quest for Bash excellence, here is your script cleaned up a bit. It will ignore commands without any whatis output. For commands with multiple whatis entries, it will only display the first. Using $((++count)) allows for increment and output at the same time.

      while IFS= read command; do
    what=$(whatis $command 2>/dev/null | head -n1 | awk -F'- ' '{print $2}')
    [[ -n $what ]] && echo "[$((++count))] $command - $what"
done < <(compgen -c | sort)
      Reply

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