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The bash Shell
 

Why bash?
  • most like sh (the Bourne shell - named for its inventor Steven Bourne) - and sh is available on every Linux/Unix system
  • command history and editing (vi or emacs style)
  • job control
  • superset of sh, ksh and csh functionality
  • tab expansion
  • key bindings
 Startup Files  

/etc/profile System Profile
~/.bash_profile Primary User Profile
~/.bash_login Alternate User Profile
~/profile Second Alternate User Profile
~/.bashrc Subshell Profile
~/.bash_logout Shell Exit Commands
. ~/.bash_profile
source ~/.bash_profile		 Re-read configuration files


Environment Variables  
[user@host user]$ env
HISTSIZE=1000
HOSTNAME=host
LOGNAME=user
HISTFILESIZE=1000
MAIL=/var/spool/mail/user
TERM=xterm
HOSTTYPE=i386
PATH=/bin:/usr/bin:/usr/local/bin:/usr/bin/X11:/usr/X11R6/bin
HOME=/home/user
INPUTRC=/etc/inputrc
SHELL=/bin/bash
PS1=[\u@\h \W]\$ 
USER=user
LC_ALL=en_US
LANG=en_US
OSTYPE=Linux
LINGUAS=en_US
SHLVL=1
_=/usr/bin/env
[user@host user]$ export MYVAR='hello world'
[user@host user]$ echo $MYVAR
hello world
[user@host user]$ unset MYVAR
[user@host user]$ echo $MYVAR

[user@host user]$ MYVAR='hello world' printenv MYVAR
hello world
[user@host user]$ export CDPATH=:/usr/web
[user@host user]$ ls
[user@host user]$ cd htdocs
/usr/web/htdocs
[user@host htdocs]$
Aliases  
[user@host user]$ alias ls='ls --color'
[user@host user]$ alias l='ls -alF'
[user@host user]$ alias cc='/usr/bin/gcc -Wall -ansi -pedantic'
[user@host user]$ alias
alias cc='/usr/bin/gcc -Wall -ansi -pedantic'
alias l='ls -alF'
alias ls='ls --color'
[user@host user]$ unalias cc
[user@host user]$ alias cc
alias: `cc' not found
Options  
[user@host user]$ set -o
[user@host user]$ help set
Functions  

[user@host user]$ declare -f mc
mc () 
{ 
    mkdir -p ~/.mc/tmp 2>/dev/null;
    chmod 700 ~/.mc/tmp;
    MC=~/.mc/tmp/mc$$-"$RANDOM";
    /usr/bin/mc -P "$@" >"$MC";
    cd "`cat $MC`";
    rm "$MC";
    unset MC
}
[user@host user]$ unset -f mc
[user@host user]$ declare -f mc
[user@host user]$ function demofunc
> {
> echo demofunc got ${#} positional parameters
> while [ ${#} -gt 0 ]
> do
> echo "${1}"
> shift
> done
> }
[user@host user]$ declare -f demofunc 
demofunc () 
{ 
    echo demofunc got ${#} positional parameters;
    while [ ${#} -gt 0 ]; do
        echo "${1}";
        shift;
    done
}
[user@host user]$ demofunc a b c
demofunc got 3 positional parameters
a
b
c
Misc - Prompting  

\tthe current time in HH:MM:SS format
\dthe date in "Weekday Month Date" format (e.g., "Tue May 26")
\nnewline
\sthe name of the shell, the basename of $0 (the portion following the final slash)
\wthe current working directory
\Wthe basename of the current working directory
\uthe username of the current user
\hthe hostname
\#the command number of this command
\!the history number of this command
\$if the effective UID is 0, a #, otherwise a $
\nnnthe character corresponding to the octal number nnn
\\a backslash
\[begin a sequence of non-printing characters, which could be used to embed a terminal control sequence into the prompt
\]end a sequence of non-printing characters

My favorite: 
[user@host user]$ export PS1="\! \t\w> "
Misc - Redirection  

Redirect Standard Input
[user@host user]$ sort < /etc/passwd

Redirect Standard Output
[user@host user]$ ls > dirlist

Append to a File
[user@host user]$ ls /etc >> dirlist

Redirect Standard Error
[user@host user]$ ls /no_such_directory 2> /dev/null

Redirect Standard Output and Standard Error
[user@host user]$ ls / /no_such_directory > dirlist 2> /dev/null

Redirect Standard Output and Standard Error to the same place
[user@host user]$ ls / /no_such_directory > dirlist 2>&1
- or -
[user@host user]$ ls / /no_such_directory &> dirlist

Pipeline
[user@host user]$ du -sk * | sort -rn | head -5

Redirect Standard Input and Pipeline
[user@host user]$ awk -F: '{print $7}' < /etc/passwd | sort | uniq


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