Shell Scripting

Basics of Shell Scripting

Create file using below commands

touch myfirstscript.sh

open and edit it in vi editor (Insert mode- I)

#!/bin/sh # This is a comment! echo Hello World    # This is a comment, too!

Try to execute it

# ./myfirstscript.sh

-bash: ./t1.sh: Permission denied

Give execute permission

chmod +x myfirstscript.sh 

Sometime we may encounter with below error while executing shell script.
-bash: ./t2.sh: /bin/sh^M: bad interpreter: No such file or directory

Solution:

Open vi in command mode (ESC)
:set fileformat=unix

Save:x! or :wq!

Example 1:Script( t1.sh) 

Command 'ls' and 'pwd' is executed when we execute the scrip t1.sh file

#!/bin/sh echo list directory ls echo Current Directory pwd echo Thanks

Output:

# ./t1.sh list directory myfirstscript.sh  t1.sh  t2.sh Current Directory / Backup/test Thanks

Example 2:

Script( t2.sh) (use of variable)

#!/bin/sh echo what is your name? read name echo Great, $name echo Welcome to our community!!

Execute : ./t2.sh

Output:

what is your name? Devyan Great, Devyan Welcome to our community!!

Example 3:

Search any file by the name in the directory:

The syntax to store the command output into a variable is var=$(command).

Files must be present in the location:

A1_test1_abc.txt will move to A1 folder

A2_test2_abc.txt will move to A2 folder

(example3.sh)

#!/bin/sh # This is a comment! echo "Provide filename to be search" read name echo "Searching your file, $name" find . -type f -name "$name*"

Output:

[root@ test]# ./example3.sh Provide filename to be search A1 Searching your file, A1 ./A1_test1_abc.txt

Example 4:

Move file to some other folder by reading their prefix name

#!/bin/sh
find /TEST/incoming/finished -name "*" -mtime +7 -exec mv {} /TEST/incoming/finished_backup/  \;

Script to fetch http reponse code 


#!/bin/sh
url=$1
curl -sL $url -w "%{http_code} %{url_effective}\\n" "URL" -o /dev/null


./testurl https://unix.stackexchange.com