What is /etc/shells ?

I use a shell called zsh. A coworker recommended it to me over 5 years ago and claimed it greatly improved his productivity. But how can a shell improve your productivity? And why would one shell with the obscure name of zsh be better than the other obscure shells bash, zsh, ksh or tcsh?

What is a shell?

A shell is an interpretor that gives a user an interface into the operating system so that the user can run commands and input data. It also supports programming and interactive use.

How do you configure a shell?

Run Control Files like .zshrc, .bash_profile, .zlogin
Environment variables like $EDITOR, $HOME, $PAGER
Aliases
Options

What is $PS1?

$PS1 stands for Prompt String 1 and it is the environment variable that defines the format of the prompt string.

For example, mine is:

$ echo $PS1
%(!.%{$fg_bold[red]%}.%{$fg_bold[green]%}%n@)%m %{$fg_bold[blue]%}%(!.%1~.%~) $(git_prompt_info)
%_$(prompt_char)%{$reset_color%}

This renders a prompt string that looks like looks like:

jasonloo@CodeMachine ~/projects/Nosajool.github.io (master*)
$

/etc/shells

/etc/shells is a file which contains the path of valid login shells.

jasonloo@CodeMachine /etc
$ cat shells
# List of acceptable shells for chpass(1).
# Ftpd will not allow users to connect who are not using
# one of these shells.

/bin/bash
/bin/csh
/bin/dash
/bin/ksh
/bin/sh
/bin/tcsh
/bin/zsh

Here are the shells my operating system supports out of the box.

shell	full name	description
bash	Bourne Again Shell	The revision of the Bourne Shell. Command line editing.
csh	C Shell	Based on the C programming language.
dash	Debian Almquist Shell	Lightweight shell written by Kenneth Almquist in late 1980s.The default shell for Ubuntu in 2006.
ksh	Korn Shell	Merged features from C Shell, TC Shell, Bourne shell. Developed before BASH.
sh	Bourne Shell	Bourne Shell. Default shell for 1979 Version 7 Unix.
tcsh	TC Shell	Enhanced C Shell.
zsh	Z Shell	Extended Bourne shell with features from Bash, ksh, tcsh. Command-line completion, shared command history, file globbing

zsh

I use zsh, the Z Shell. Some of the features of this shell are:

Autocomplete

I can type

$ cd /bi

and use completion to auto complete to `cd /bin`.

Up History

I often use <CTRL>+R for recursive search history but you can also use <UP> and <DOWN> arrows.

Arguments without using –help

ps -<TAB> gives you a quick look at the arguments for a command.

$ ps -
C     -- ignore resident time for CPU percentage
E     -- show environment after command
L     -- display all format specifiers
M     -- show threads corresponding to each process
S     -- include child process data with the parent
T     -- select processes attached to current terminal
X     -- skip processes with no controlling terminal
a     -- include processes belonging to other users
c     -- show just executable name for command
d     -- select all processes except session leaders
e  A  -- select every process
f     -- full listing
h     -- repeat header lines, one per page of output
j     -- output in job control format
l     -- output in long format
m     -- sort by memory usage
r     -- sort by CPU usage
v     -- output in virtual memory format
w     -- wide output
x     -- include processes with no controlling terminal
G  -- select processes by real group
O  -- specify additional output fields
U  -- select processes by real user
g  -- select processes by process group leader
o  -- specify output format
p  -- select processes by ID
t  -- select processes by attached terminal
u  -- select processes by user id

Using editor for long commands

You can use <CTRL>X<CTRL>E to edit the current command in your default text editor. Whenever I start chaining commands with && or start writing a loop, I use this.

Oh My Zsh

Oh My Zsh is not a feature but a community driven framework for managing Zsh configuration. I use it for themes and plugins. There are are also helper functions that can be used to improve your workflows.