Following steps are required to write shell script:
(1) Use any editor like vi or mcedit to write shell script.
(2) After writing shell script set execute permission for your script as follows
syntax:
chmod permission your-script-name
syntax:
chmod permission your-script-name
Examples:
$ chmod +x your-script-name
$ chmod 755 your-script-name
Note: This will set read write execute(7) permission for owner, for group and other permission is read and execute only(5).
(3) Execute your script as
syntax:
bash your-script-name
sh your-script-name
./your-script-name
syntax:
bash your-script-name
sh your-script-name
./your-script-name
Examples:
$ bash bar
$ sh bar
$ ./bar
NOTE In the last syntax ./ means current directory, But only . (dot) means execute given command file in current shell without starting the new copy of shell, The syntax for . (dot) command is as follows
Syntax:
. command-name
Syntax:
. command-name
Example:
$ . foo
Now you are ready to write first shell script that will print "Knowledge is Power" on screen.
$ vi first
#
# My first shell script
#
clear
echo "Knowledge is Power"
After saving the above script, you can run the script as follows:
$ ./first
This will not run script since we have not set execute permission for our script first; to do this type command
$ chmod 755 first
$ ./first
First screen will be clear, then Knowledge is Power is printed on screen.
Script Command(s)
|
Meaning
|
| $ vi first | Start vi editor |
| # # My first shell script # | # followed by any text is considered as comment. Comment gives more information about script, logical explanation about shell script. Syntax: # comment-text |
| clear | clear the screen |
| echo "Knowledge is Power" | To print message or value of variables on screen, we use echo command, general form of echo command is as follows syntax: echo "Message" |
Tip: For shell script file try to give file extension such as .sh, which can be easily identified by you as shell script.
