Quick start bash script

Quick Start - Bash Script
Simon Su

● Not a linux/unix guide ...
● Talk something basic about programming
shell script ...
○ Basic concepts
○ Basic commands
○ Vi
Outline

Shell Scripts
● sh
● bash
● ksh
● csh
● zsh
sh csh ksh bash tcsh zsh rc es
Job control N Y Y Y Y Y N N
Aliases N Y Y Y Y Y N N
Shell functions Y(1) N Y Y N Y Y Y
"Sensible" Input/Output redirection Y N Y Y N Y Y Y
Directory stack N Y Y Y Y Y F F
Command history N Y Y Y Y Y L L
Command line editing N N Y Y Y Y L L
Vi Command line editing N N Y Y Y(3) Y L L
Emacs Command line editing N N Y Y Y Y L L
Rebindable Command line editing N N N Y Y Y L L
User name look up N Y Y Y Y Y L L
Login/Logout watching N N N N Y Y F F
Filename completion N Y(1) Y Y Y Y L L
Username completion N Y(2) Y Y Y Y L L
Hostname completion N Y(2) Y Y Y Y L L
History completion N N N Y Y Y L L
Fully programmable Completion N N N N Y Y N N
Mh Mailbox completion N N N N(4) N(6) N(6) N N
Co Processes N N Y N N Y N N
Builtin artithmetic evaluation N Y Y Y Y Y N N
Can follow symbolic links invisibly N N Y Y Y Y N N
Periodic command execution N N N N Y Y N N
Custom Prompt (easily) N N Y Y Y Y Y Y
Sun Keyboard Hack N N N N N Y N N
Spelling Correction N N N N Y Y N N
Process Substitution N N N Y(2) N Y Y Y
Underlying Syntax sh csh sh sh csh sh rc r
Freely Available N N N(5) Y Y Y Y Y
Checks Mailbox N Y Y Y Y Y F F
Tty Sanity Checking N N N N Y Y N N
Can cope with large argument lists Y N Y Y Y Y Y Y
Has non-interactive startup file N Y Y(7) Y(7) Y Y N N
Has non-login startup file N Y Y(7) Y Y Y N N
Can avoid user startup files N Y N Y N Y Y Y
Can specify startup file N N Y Y N N N N
Low level command redefinition N N N N N N N Y
Has anonymous functions N N N N N N Y Y
List Variables N Y Y N Y Y Y Y
Full signal trap handling Y N Y Y N Y Y Y
File no clobber ability N Y Y Y Y Y N F
Local variables N N Y Y N Y Y Y
Lexically scoped variables N N N N N N N Y
Exceptions N N N N N N N Y

Basic Concept -
.bashrc / .bash_profile / .bash_history
● .bashrc
● .bash_profile
● .bash_history

Basic Concept - man page
● man [commands]
ex: man bash

Basic Concept - Declare & Comment
● #!/bin/bash
● #comments...

Basic Concept - Environment
● export KEY=VALUE

Basic Concept - source
● . [script file]
● source [script file]

Basic Concept - “|”
● ps -ef | grep root
● ps -ef | cat > /tmp/ps.log
● ps -ef | grep httpd | awk '{print $2}'

Basic Concept - “<” & “>” & “>>”
● mysql -uroot -p < test.sql
● ps -ef > ps.log
● bash [file] > /dev/null 2>&1
● ps -ef >> ps.log

Basic Concept - `[commands]`
● kill -9 `ps -ef | grep httpd | awk ‘{print $2}’`
● tail -f `svcs -L apache`

Basic Concept - ‘’ & “”

Basic Concept - & and &&
● bash [file] &
● bash [file1] && bash [file2]

Basic Concept - bash execution
● #!/bin/bash
● ./[file]
● bash [file]
● bash -x [file]

Basic Concept - Parameter input
● Input:
bash [file] [parameter 1] [parameter 2] …
● Receive:
$1, $2....

Basic Concept - Parameters of Bash
● $#
● $@
● $*
● $?

● alias ll=”ls -l”
Basic Commands - alias

Basic Commands - bg / fg
Process lock
screen..
ctrl + z
(process stop and
screen return)
bg
(process keep
running)
fg
(screen back to
process)

Basic Commands - background proc
● bash [script file] &
● nohup bash [script file] &
● nohup bash [script file] > /dev/null 2>&1 &

if …. then … elseif … fi
export i=5;
if [ $i -gt 5 ] ; then echo $i; fi
if [ $i -eq 5 ] ; then echo $i; fi
if Expression
then
Commands
elif Expression
then
Commands
else
Commands
fi
if (Expression)
then
Commands
elif (Expression)
then
Commands
else
Commands
fi
if [ Expression ]; then
Commands
elif [ Expression ]; then
Commands
else
Commands
fi

for / while / until loop
for name in { 1..10 }
do
….
done
for VariableName in List
do
Commands
done
while [Expression]
do
Commands
done
until [ Expression ]
do
Commands
done

function
helloworld(){
echo hello $1
}
helloworld simon

Basic Commands - find
● find [from] -name [pattern] -print
● find [from] -name [pattern] -type f
● find [from] -ctime 3 -print
● find [from] -atime +1 -print -exec ls -l {} ;

Basic Commands - awk
● awk -F "t" '{print $1,$2}' /etc/hosts
● cat /etc/hosts | awk -F "t" '{print $1,$2}'

Basic Commands - sed
● sed 's/old_text/new_text/g' [file]
● sed -i 's/old_text/new_text/g' [file]

Basic Commands - xargs
● ps -ef | grep node | awk '{print $2}' | xargs kill -9

Nice tool - bash_it
● https://github.com/revans/bash-it
● Install:
○ Check a clone of this repo:
git clone http://github.com/revans/bash-it.git ~/.bash_it
○ Run ~/.bash_it/install.sh
○ Edit your ~/.bash_profile file in order to customize bash-it.

Vi - Goto line & Search & Replace
● Goto line:
:[line number]
● Search:
/[key]
● Replace first:
%s/[old]/[new]
● Replace all:
%s/[old]/[new]/g

Vi - split, vsplit
● :vsp
● :vsp [file]
● :sp
● :s[ [file]
● ctrl+w

Vi - tabedit
● :tabe [file]
● gt
● n gt

Vi - set
● :set nu / :set nonu
● :set paste

Vi - execute command
● :![command]

Quick start bash script

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