Setting shell options

• Task: Make changes to your bash shell environment using set and shopt commands.


• The set and shopt command controls several values of variables controlling shell behavior.

Contents

• List currently configured shell options
  
  • 1.1 How do I set and unset shell variable options?
    
    • 1.1.1 Examples


• 2 shopt command
  
  • 2.1 How do I enable (set) and disable (unset) each option?
    
    • 2.1.1 Examples


• 3 Customizing Bash environment with shopt and set
  
  • 3.1 How do I setup environment variables?

List currently configured shell options

Type the following command:

set -o

Sample outputs:

allexport      	off

braceexpand    	on

emacs          	on

errexit        	off

errtrace       	off

functrace      	off

hashall        	on

histexpand     	on

history        	on

ignoreeof      	off

interactive-comments	on

keyword        	off

monitor        	on

noclobber      	off

noexec         	off

noglob         	off

nolog          	off

notify         	off

nounset        	off

onecmd         	off

physical       	off

pipefail       	off

posix          	off

privileged     	off

verbose        	off

vi             	off

xtrace         	off

• See set command for detailed explanation of each variable.

How do I set and unset shell variable options?

To set shell variable option use the following syntax:

set -o variableName

To unset shell variable option use the following syntax:

set +o variableName

Examples

Disable <CTRL-d> which is used to logout of a login shell (local or remote login session over ssh).

set -o ignoreeof

Now, try pressing [CTRL-d]
Sample outputs:

Use "exit" to leave the shell.

Turn it off, enter:

set +o ignoreeof

shopt command

You can turn on or off the values of variables controlling optional behavior using the shopt command. To view a list of some of the currently configured option via shopt, enter:

shopt

shopt -p

Sample outputs:

cdable_vars    	off

cdspell        	off

checkhash      	off

checkwinsize   	on

cmdhist        	on

compat31       	off

dotglob        	off

execfail       	off

expand_aliases 	on

extdebug       	off

extglob        	off

extquote       	on

failglob       	off

force_fignore  	on

gnu_errfmt     	off

histappend     	off

histreedit     	off

histverify     	off

hostcomplete   	on

huponexit      	off

interactive_comments	on

lithist        	off

login_shell    	off

mailwarn       	off

no_empty_cmd_completion	off

nocaseglob     	off

nocasematch    	off

nullglob       	off

progcomp       	on

promptvars     	on

restricted_shell	off

shift_verbose  	off

sourcepath     	on

xpg_echo       	off

How do I enable (set) and disable (unset) each option?

To enable (set) each option, enter:

shopt -s optionName

To disable (unset) each option, enter:

shopt -u optionName

Examples

If cdspell option set, minor errors in the spelling of a directory name in a cd command will be corrected. The errors checked for are transposed characters, a missing character, and one character too many. If a correction is found, the corrected file name is printed, and the command proceeds. For example, type the command (note /etc directory spelling):

cd /etcc

Sample outputs:

bash: cd: /etcc: No such file or directory

Now, turn on cdspell option and try again the same cd command, enter:

shopt -s cdspell

cd /etcc

Sample outputs:

/etc

[vivek@vivek-desktop /etc]$

Customizing Bash environment with shopt and set

Edit your ~/.bashrc, enter:

vi ~/.bashrc

Add the following commands:

# Correct dir spellings

shopt -q -s cdspell



# Make sure display get updated when terminal window get resized

shopt -q -s checkwinsize



# Turn on the extended pattern matching features 

shopt -q -s extglob



# Append rather than overwrite history on exit

shopt -s histappend



# Make multi-line commandsline in history

shopt -q -s cmdhist 



# Get immediate notification of background job termination

set -o notify 



# Disable [CTRL-D] which is used to exit the shell

set -o ignoreeof



# Disable core files

ulimit -S -c 0 > /dev/null 2>&1

How do I setup environment variables?

Simply add the settings to ~/.bashrc:

 # Store 5000 commands in history buffer

export HISTSIZE=5000



# Store 5000 commands in history FILE 

export HISTFILESIZE=5000      



# Avoid duplicates in hisotry 

export HISTIGNORE='&:[ ]*'



# Use less command as a pager

export PAGER=less



# Set vim as default text editor

export EDITOR=vim

export VISUAL=vim

export SVN_EDITOR="$VISUAL"



# Oracle database specific 

export ORACLE_HOME=/usr/lib/oracle/xe/app/oracle/product/10.2.0/server

export ORACLE_SID=XE

export NLS_LANG=$($ORACLE_HOME/bin/nls_lang.sh)



# Set JAVA_HOME 

export JAVA_HOME=/usr/lib/jvm/java-6-sun/jre



# Add ORACLE, JAVA and ~/bin bin to PATH

export PATH=$PATH:$ORACLE_HOME/bin:$HOME/bin:$JAVA_HOME/bin



# Secure SSH login stuff using keychain

# No need to input password again ever

/usr/bin/keychain $HOME/.ssh/id_dsa

source $HOME/.keychain/$HOSTNAME-sh



# Turn on Bash command completion

source /etc/bash_completion



# MS-DOS / XP cmd like stuff

alias edit=$VISUAL

alias copy='cp'

alias cls='clear'

alias del='rm'

alias dir='ls'

alias md='mkdir'

alias move='mv'

alias rd='rmdir'

alias ren='mv'

alias ipconfig='ifconfig'



# Other Linux stuff

alias bc='bc -l'

alias diff='diff -u'



# get updates from RHN

alias update='yum -y update'



# set eth1 as default

alias dnstop='dnstop -l 5  eth1'

alias vnstat='vnstat -i eth1'



# force colorful grep output

alias grep='grep --color'



# ls stuff

alias l.='ls -d .* --color=tty'

alias ll='ls -l --color=tty'

alias ls='ls --color=tty'

Auteur : Harlok

2019-05-10 16:43:07