functions.md

Functions

User defined functions allow you to take snippets of code and reuse them. This is similar to any programming language and has the following benefits over aliases.

Functions can:

• accept parameters (e.g. $1, $2...)
• have control logic (e.g. case and if)
• spawn subshells
• have error codes and traps

Functions are a building block for a lot of zsh. Two major aspects of zsh are widgets and hooks which are both uses of functions.

We'll only show some basics and examples here because it's assumed you know how create shell functions.

Basics

Hopefully you know the dozen different ways to declare a function.

# declare ffoo function
function ffoo() { echo foo; }

# declare fbar function
fbar() { echo bar; }

# Anonymous function
() { echo baz; }

Nothing goes between the () and nothing is returned in traditional function definitions. You can set a global variable from within the function or echo a value in the function and use a subshell to store its value.

function to-lower() {
    echo ${1:l}
}

var=$(to-lower FOO)

echo $var
foo

Print a Function

Sometimes you can't remember what's in a function or where it's sourced from. To print a shell function to stdout you can use type -f or whence -f. Both are zsh builtin commands.

echo 'do-ls() { emulate -L zsh; \ls; }' > do-ls

source ./do-ls

whence -f do-ls
do-ls () {
    emulate -L zsh
    \ls
}

It's also handy to know where a function comes from. Sometimes you can't remember what file it was sourced in if you need to edit it.

To print the file it came from use whence -v

whence -v do-ls
do-ls is a shell function from ./do-ls

# if you declare the function directly you won't
# see the path with -v
do-ls() { emulate -L zsh; \ls; }

whence -v do-ls
do-ls is a shell function

Examples

Here are some examples of functions I have found fun or handy.

Many of these functions require external programs like fzf. Make sure you have them installed in your $PATH if you want to use them.

Show website certificate from hostname

function curl-cert() {
  openssl s_client -showcerts -connect "${1}":443 -servername ${1}
}

Interactively export AWS_PROFILE

function awsp() {
    export AWS_PROFILE=$(grep profile ${HOME}/.aws/config \
        | awk '{print $2}' | sed 's,],,g' \
        | fzf --layout reverse --height=10% --border)
}

Interactive man search

function  mans(){
    man -k . \
    | fzf -n1,2 --preview "echo {} \
    | cut -d' ' -f1 \
    | sed 's# (#.#' \
    | sed 's#)##' \
    | xargs -I% man %" --bind "enter:execute: \
      (echo {} \
      | cut -d' ' -f1 \
      | sed 's# (#.#' \
      | sed 's#)##' \
      | xargs -I% man % \
      | less -R)"
}

Interactive git diff

function fshow() {
  git log --graph --color=always \
      --format="%C(auto)%h%d %s %C(black)%C(bold)%cr" "$@" \
  | fzf --ansi --preview "echo {} \
    | grep -o '[a-f0-9]\{7\}' \
    | head -1 \
    | xargs -I % sh -c 'git show --color=always %'" \
        --bind "enter:execute:
            (grep -o '[a-f0-9]\{7\}' \
                | head -1 \
                | xargs -I % sh -c 'git show --color=always % \
                | less -R') << 'FZF-EOF'
            {}
FZF-EOF"
}

The most important functions

disappointed() { echo -n " ಠ_ಠ " |tee /dev/tty| xclip -selection clipboard; }

flip() { echo -n "（╯°□°）╯ ┻━┻" |tee /dev/tty| xclip -selection clipboard; }

shrug() { echo -n "¯\_(ツ)_/¯" |tee /dev/tty| xclip -selection clipboard; }

matrix() { echo -e "\e[1;40m" ; clear ; while :; do echo $LINES $COLUMNS $(( $RANDOM % $COLUMNS)) $(( $RANDOM % 72 )) ;sleep 0.05; done|awk '{ letters="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789@#$%^&*()"; c=$4;        letter=substr(letters,c,1);a[$3]=0;for (x in a) {o=a[x];a[x]=a[x]+1; printf "\033[%s;%sH\033[2;32m%s",o,x,letter; printf "\033[%s;%sH\033[1;37m%s\033[0;0H",a[x],x,letter;if (a[x] >= $1) { a[x]=0; } }}' }

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