Shell Scripting

FOSS / LAMP

Session 4

Shell Scripting

Scripting Basics • Shell scripts are text files that contain a series of commands or statements to be executed. • It is useful for – To automate – Creating applications – Perform system administration

Creating shell scripts • Text editor vi is used to create a text file containing commands • Executing script $ bash filename

• Make the script executable $ chmod a+x filename

Examples $ vi file1 echo "enter the source file" read f1 echo "enter the destination file" read f2 cp $f1 $f2 echo "file is copied"

$ vi file2 read -p "enter source file" f1 read -p "enter destination file" f2 mv $f1 /opt/$f2 echo "file is moved"

If statements $ vi file3 read a read b if [ $a -gt $b ] ; then echo "a is greater $a"; else echo "b is greater $b"; fi

Nested If • $ vi file4 read a b c if [ $a -gt $b ] && [ $a -gt $c ]; then echo “ a is greater $a”; elif [ $b -gt $a ] && [ $b -gt $c ]; then echo “b is greater $b”; else echo “c is greater $c”; fi

For loop $ vi file5 for i in {0..5}

for i in $(seq 1 2 10)

do

do

echo "$i";

echo "$i";

done

done

• $ vi file6 read n for ((i=1; i<=$n; i++)) do echo "$i"; done

While loop $ vi file6

while [ $i -le $n ]

echo "how many users you want to add"

do

read n

useradd $name$i

echo "enter the stating name of the user"

i=`expr $i + 1`

read name i=1

echo " creatibng user $name$i"

done

Case Statement • $ vi file8 read choice echo "enter the num1 num2" read n1 n2 case $choice in 1)echo "ADD : ` expr $n1 + $n2 `";; 2)echo “MUL : ` expr $n1 \* $n2 `”;; esac

Thanks a lot for your attention !!