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How to define/undefine an alias/function in bash

in «tip» by Michael Beard
Tags: , , , , , ,

So many interesting things to learn here.

I knew about aliases and use them all the time. I had forgotten how to undefine them though, so ...

alias

Here is how to define one:

alias someaction="some sort of action or something here"

You use it like you'd expect. At the command-line, just enter someaction and it will do it's thing! Very nice.

Once you've defined it and you don't want or need it anymore, remove it by:

unalias someaction

It's as easy as that. If you want to know all of the aliases you've got defined, what you need to do is type

  • alias
  • declare -f alias
  • declare -a

at the command-line and it will list all of the currently defined aliases.

shell functions

Now, one thing I hadn't ever really thought about is that you can define functions (called shell functions) in the terminal! Here is an example:

export MY_BIN_DIR="/Users/$(whoami)/.mike/my_setup/bin"

#### by arunkumar AND Evan Langlois (2 entries)
#### from: https://stackoverflow.com/questions/7131670/make-a-bash-alias-that-takes-a-parameter
#### -------------------
#### will execute the first parameter and pass any other parameters beyond
#### that into the function (or, at least, that is the hope)
mybin() {
    ${MY_BIN_DIR}/$@
}

You can find out all of the different shell functions you have in a couple of different ways:

  • use the declare command
    • use the -F option (i.e. -- declare -F) to list all of the names of the shell functions that are defined
    • use the -f option (i.e. -- declare -f) to list the source and names of all of the shell functions that are defined
  • for searching for (I suppose - didn't see this listed, but tried it and it works) a specific name to see if a shell function of that names exists, then, use
    • declare -F func_name and if it exists, it will return it and if not, it will return nothing
    • compgen -A function - will display the name of the functions
    • set | grep " ()"
  • for listing the source of a shell function there are (again) several ways
    • declare -f func_name* - will display the source of the function, if** it exists
    • type func_name

Here is an interesting shell function that will list all of the defined shell functions and aliases. Very neat:

function functionaliaslist() {
    echo
    echo -e "\033[1;4;32m""Functions:""\033[0;34m"
    compgen -A function
    echo
    echo -e "\033[1;4;32m""Aliases:""\033[0;34m"
    compgen -A alias
    echo
    echo -e "\033[0m"
}

awesome links