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Shell Script Examples

Bourne Again Shell (bash) is the common shell used in Unix/Linux based Operating Systems. Also these days, even Windows OS also comes with an option called Power Shell.  This post will list out some basic exercises that a shell can do. Do follow this blog with more number of exercises.
To run a bash file, you can use either of these following commands
  • bash file.sh
  • sh file.sh
  • ./file.sh (in this case the file.sh should be made executable)
For making executable file, use this command chmod 755 file.sh
1. A Shell to Handle a File, rename a given file, compress it and move it to a newfolder and decompress it in the newfolder
   1: #!/bin/bash
   2: touch pri.txt
   3: ls >; pri.txt
   4: mv pri.txt file.doc
   5: tar zcvf compress.tar.gz file.doc
   6: mkdir newfolder/
   7: cp compress.tar.gz newfolder/
   8: cd newfolder/
   9: tar zxvf compress.tar.gz

2. A shell to find a particular string from a file and redirect it to another file.
 
#!/bin/bash
echo "Enter a string to be searched in the file : "
read search
echo "Enter a file name  : "
read name_file
grep $search $name_file > found.txt
cat found.txt

3. A shell to read a variable and process it mathematically (use of add operation).
#!/bin/bash
echo -n "Enter 1st number : "
read a
echo -n "Enter 2nd number : "
read b
c=`expr $a + $b`
echo "The value is $c"

4. A shell to Greet the user based on the system time.

#!/bin/bash
dat=`date +%H`
if [ "$dat" -lt 12 ]; 
then
echo "Good Morning"
elif [ "$dat" -lt 17 ] ;
then
echo "Good Afternoon"
else
echo "Good Evening"
fi
5. A shell to create a menu based system to control multiple commands using case esac block
#!/bin/bash
echo "What do you want to know ?"
echo "1. Today's Date"
echo "2. Today's Day"
echo "3. Time"
echo "4. Current Month"
echo "5. Current Year"
echo "6. Current Week"
echo "Enter a number to choose from the menu"
read ch
case "$ch" in
1)
dat=`date +%d`
echo "Today's date is $dat"
;;
2)
day=`date +%a`
echo "Today is $day"
;;
3)
time=`date +%T`
echo "The time now is $time"
;;
4)
mon=`date +%b`
echo "The month is $mon"
;;
5)
year=`date +%Y`
echo "The year is $year"
;;
6)
week=`date +%W`
echo "This is the $week th of the year"
;;
*)
echo "Try again"
esac
6. A shell to find the number of document files in a given directory using for loop.
#!/bin/bash
count=0;
for i in *.doc
do
count=`expr $count + 1`
done
echo "There are $count documents"
Try running these examples and get the use of SHELL.
Pradeep Kumar TS

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