A shell script is a series of bash commands that can be executed by shell. A nice tutorial for shell scripting is available at the shell tutorial and Bash scripting cheatsheet.

The first shell script “Hello World” using echo.

#!/bin/sh
echo "Hello World"

Read input from screen

#!/bin/sh
echo "What is your name?"
read NAME
echo "Hello, $NAME"

Read parameters from command lines: ./script.sh 3 alpha

#!/bin/sh
echo $1 $2
echo $@

Array variables. All shell variables should be capitalized

#!/bin/sh
NAME[0]="Zara"
NAME[1]="Qadir"
NAME[2]="Mahnaz"
NAME[3]="Ayan"
NAME[4]="Daisy"
echo "names: ${NAME[*]}"
for I in ${NAME[*]}
do
        echo $I
done

Math expression using `expr`

#!/bin/sh
val=`expr 2 + 2`
echo "Total value : $val"

Flow: make a decision if, elif, else

#!/bin/sh
NAME[0]="Zara"
NAME[1]="Qadir"
NAME[2]="Mahnaz"
NAME[3]="Ayan"
NAME[4]="Daisy"
echo "names: ${NAME[*]}"

for I in ${NAME[*]}
do
        echo $I
        if [ $I == "Ayan" ] 
        then
            break
        fi
done

Loop: for, until, while

#!/bin/sh
a=0
while [ $a -lt 10 ]
do
   echo $a
   if [ $a -eq 5 ]
   then
      break
   fi
   a=`expr $a + 1`
done

Define a function

#!/bin/sh
Hello () {
   echo "Hello World $1 $2"
}
Hello Zara Ali