You can use shell variables to store data, set configuration options and customize the shell environment under Linux. The default shell is Bash under Linux and can be used for the following purposes:
- Configure look and feel of shell.
- Setup terminal settings depending on which terminal you're using.
- Set the search path such as JAVA_HOME, and ORACLE_HOME.
- Set environment variables as needed by programs.
- Run commands that you want to run whenever you log in or log out.
- Setup aliases and/or shell function to automate tasks to save typing and time.
- Changing bash prompt.
- Setting shell options.
Display Current Environment
Type the following command:$ set
Sample outputs:
BASH=/bin/bashThe $PATH defined the search path for commands. It is a colon-separated list of directories in which the shell looks for commands. The $PS1 defines your prompt settings. See the list of all commonly used shell variables for more information. You can display the value of a variable using printf or echo command:
BASH_ARGC=()
BASH_ARGV=()
BASH_LINENO=()
BASH_SOURCE=()
BASH_VERSINFO=([0]="3" [1]="2" [2]="25" [3]="1" [4]="release" [5]="x86_64-redhat-linux-gnu")
BASH_VERSION='3.2.25(1)-release'
COLORS=/etc/DIR_COLORS.xterm
COLUMNS=237
CVS_RSH=ssh
DIRSTACK=()
EUID=0
GROUPS=()
G_BROKEN_FILENAMES=1
HISTFILE=/root/.bash_history
HISTFILESIZE=1000
HISTSIZE=1000
HOME=/root
HOSTNAME=server3.www.p.cyberciti.biz
HOSTTYPE=x86_64
IFS=$' \t\n'
INPUTRC=/etc/inputrc
LANG=en_US.UTF-8
LESSOPEN='|/usr/bin/lesspipe.sh %s'
LINES=64
LOGNAME=root
LS_COLORS='no=00:fi=00:di=00;34:ln=00;36:pi=40;33:so=00;35:bd=40;33;01:cd=40;33;01:or=01;05;37;41:mi=01;05;37;41:ex=00;32:*.cmd=00;32:*.exe=00;32:*.com=00;32:*.btm=00;32:*.bat=00;32:*.sh=00;32:*.csh=00;32:*.tar=00;31:*.tgz=00;31:*.arj=00;31:*.taz=00;31:*.lzh=00;31:*.zip=00;31:*.z=00;31:*.Z=00;31:*.gz=00;31:*.bz2=00;31:*.bz=00;31:*.tz=00;31:*.rpm=00;31:*.cpio=00;31:*.jpg=00;35:*.gif=00;35:*.bmp=00;35:*.xbm=00;35:*.xpm=00;35:*.png=00;35:*.tif=00;35:'
MACHTYPE=x86_64-redhat-linux-gnu
MAIL=/var/spool/mail/root
MAILCHECK=60
OPTERR=1
OPTIND=1
OSTYPE=linux-gnu
PATH=/usr/kerberos/sbin:/usr/kerberos/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin
PIPESTATUS=([0]="0")
PPID=35469
PROMPT_COMMAND='echo -ne "\033]0;${USER}@${HOSTNAME%%.*}:${PWD/#$HOME/~}"; echo -ne "\007"'
PS1='[\u@\h \W]\$ '
PS2='> '
PS4='+ '
PWD=/root
SHELL=/bin/bash
SHELLOPTS=braceexpand:emacs:hashall:histexpand:history:interactive-comments:monitor
SHLVL=1
SSH_CLIENT='10.1.3.116 44212 22'
SSH_CONNECTION='10.1.3.116 44212 10.10.29.68 22'
SSH_TTY=/dev/pts/0
TERM=xterm
UID=0
USER=root
_=set
consoletype=pty
tmpid=0
genpasswd ()
{
local l=$1;
[ "$l" == "" ] && l=16;
tr -dc A-Za-z0-9_ < /dev/urandom | head -c ${l} | xargs
}
xrpm ()
{
[ "$1" != "" ] && ( rpm2cpio "$1" | cpio -idmv )
}
$ echo "$HOME"
OR
$ printf "%s\n" $HOME
Sample outputs:
/home/vivek
Task: Set Environment Variables on Linux
You can modify each environmental or system variable using the export command. Set the PATH environment variable to include the directory where you installed the bin directory with perl and shell scripts:OR
export PATH=${PATH}:/home/vivek/bin
To set the JAVA_HOME environment variable to the directory where you installed the J2SE SDK application, enter:
export PATH=${PATH}:${HOME}/bin
You can set multiple paths as follows:
export PATH=${PATH}:/usr/java/jdk1.5.0_07/bin
export ANT_HOME=/path/to/ant/dir
export PATH=${PATH}:${ANT_HOME}/bin:${JAVA_HOME}/bin
How Do I Make All Settings permanent?
The ~/.bash_profile ($HOME/.bash_profile) or ~/.prfile file is executed when you login using console or remotely using ssh. Type the following command to edit ~/.bash_profile file, enter:$ vi ~/.bash_proflle
Append the $PATH settings, enter:
export PATH=${PATH}:${HOME}/bin
Save and close the file.
Set IBM DB2 Instance Name
Type the following command:
export DB2INSTANCE=prod_sales
No comments:
Post a Comment