Zsh Tips 1: Aliases and Functions

Esperanto · English
October 18, 2017
Last updated: Septembro 26, 2018

A common man marvels at uncommon things; a wise man marvels at the commonplace.
―Confucius

One of the joys of working exclusively on the terminal is makes it so easy to work with commands, files, and directories. Being able to go from idea to results happens in a very short span of time. For interactive shell use, I use Zsh almost exclusively. In this article, I’ll talk about some things to improve your interactive interaction with the shell.

Table of contents

Overview

There are at least three kinds of commands in Zsh: binaries, aliases, and functions. Binaries are the ones that are found in your $PATH; they are the programs that you installed using your package manager. Aliases and functions, or other other hand do not live as files on the filesystem. They are defined as part of your configuration file, or inlined in your session.

Aliases

Aliases are those cute stupid things that you put in your config files that usually do trivial one liners. Some of them look like the following:

alias ls="ls -F"

Other are more aggressive like the global aliases, which can perform expansion anywhere on the command line:

alias -g G="|& egrep --color"
alias -g NF='*(.om[1])'

The first global alias filters the stdout and stderr to egrep with colored output. The second global alias matches the newest regular file in the current directory.

To display all your aliases, run:

alias

Functions

Functions on the other hand are the bigger relatives of aliases. They can do more than what their lesser ilk, can. One of the most important differences to note is that functions perform more that substitution. For example, an alias like the following:

alias meh="echo foo"

simply performs text substitution. That is, when Zsh encounters the text foo as the first token of the command line, it replaces it with echo foo. Nothing more. So, running:

meh foo

substitutes to

echo foo

Compare the following lines:

alias foo0="for x in foo bar baz; do echo $x; done"
function foo1 () { for x in foo bar baz; do echo $x; done }

The keyword function is redundant and may be omitted. Run them and see what happens:

% foo0
% foo1

Aliases have a higher priority than functions. Consider the following lines:

alias foo="echo foo"
function foo () { echo foo, too }

Both use the name foo, but each uses a different namespace. When you execute foo:

% foo
foo

It displays just foo because, instead of foo, too even if the latter came from a more recent definition. To remove the foo alias definition, run:

% unalias foo
% foo
foo, too

As much as possible, use functions.

To display all your functions, run:

% functions

Putting them all together

Littering your config file with complete function definitions for every little command that you want is dumb. Instead, we’ll use a better way to define global aliases and small functions. Open your ~/.zshenv file using your favorite editor.

First let’s define the functions that will define the others.

function def_real_alias () {
  while [[ $# -ge 2 ]]; do
    alias "$1=$2"
    shift 2
  done
}

function def_real_aliases () {
  def_real_alias $real_aliases
  unset real_aliases
}

function def_global_alias () {
  while [[ $# -ge 2 ]]; do
    alias -g "$1=$2"
    shift 2
  done
}

function def_global_aliases () {
  def_global_alias $global_aliases
  unset global_aliases
}

function def_fun () {
  while [[ $# -ge 2 ]]; do
    eval "function $1 () { $2 \[email protected] }"
    shift 2
  done
}

function def_funs () {
  def_fun $funs
  unset funs
}

Next we’ll define the arrays:

real_aliases=(
  meh "echo meh"
); def_real_aliases

global_aliases=(
  :: ':>!'

  B '`git rev-parse --abbrev-ref HEAD`'

  V "|& less"
  G "|& egrep --color"
  S "|& sort"
  R "|& sort -rn"
  L "|& wc -l | sed 's/^\ *//'"

  H  "|& head"
  T  "|& tail"
  H1 "H -n 1"
  T1 "T -n 1"

  ZF '*(.L0)'     # zero-length regular files
  ZD '*(/L0)'     # zero-length directories

  AE '{,.}*'      # all files, including dot files
  AF '**/*(.)'    # all regular files
  AD '**/*(/)'    # all directories
  AS '**/*(@)'    # all symlinks

  OF '*(.om[-1])' # oldest regular file
  OD '*(/om[-1])' # oldest directory
  OS '*(@om[-1])' # oldest symlink

  NF '*(.om[1])'  # newest regular file
  ND '*(/om[1])'  # newest directory
  NS '*(@om[1])'  # newest symlink

); def_global_aliases

funs=(
  z "exec zsh"
  s "sudo"

  d "pushd"
  \- "popd"
  ds "dirs -l"

  cp "command cp -i"
  mv "command mv -i"

  l "ls -GFAtr --color"
  la "ls -AF --color"
  ll "l -l
  l1 "l -1"
  lh "l -H"
  lr "l -R"
  lk "la -l"

  sl "ln -sf"
  md "mkdir -p"

  f "fd"
  g "ripgrep --color auto"
  gi "g -i"
  tf "tail -F"
  rh "rehash"

  mount "s mount"
  umount "s umount"
  reboot "s reboot"
  poweroff "s poweroff"
  halt "s halt -p"
); def_funs

Closing remarks

Grouping commands this way makes it significantly easier to add and remove items. Bring them all in one consolidated place also makes your config file arguably cleaner. For the rest of the definitions, visit the repo here.