Sunday, December 6, 2009

Create and Run a Linux Script to Run Linux Commands

Creating and running a Linux script to automatically run a series of Linux commands that you commonly run is easy! With a Linux script, you put a series of routinely run commands in a text file, and then run all of them by simply typing in the name of the file and pressing Enter.
1. Run a Linux text editor.
2. Put the following text at the top left of the text file (indented below for emphasis):
This indicates that the text file is a Linux script file.
Press Enter twice to have a blank line below the line above.
3. Put the Linux command(s) in the script file.
The Linux commands below are used to provide an example. You can put any commands in a script.
The Linux commands below will: clear the screen, change into the /etc directory path, and then show the current path with the Linux pwd (path to working directory) command.
Then provide a long list of the fstab file (to show you that it’s there) and then change into your home directory (represented by the ~ symbol) and then show the path of the current directory.
The Linux echo command is not required, but has been put in the file to show the progress of the execution of the script. Also, you don’t need to indent the commands below in the Linux script – they are just indented here for emphasis.
echo The screen has been cleared
cd /etc
echo This is the etc directory
ls -l fstab
echo This is a long listing of the fstab file
cd ~
pwd echo Now in my home directory
Linux Commands Training Tips: A Linux script can contain hundreds of lines of text if necessary – and also include complex programming logic, such as if . . . then statements.
4. Save the text / script file with a meaningful name to create it and by give it a name.
For example, if you want to list files in a few directories, call the file: listdirs
5. Run the Linux chmod command to change the permissions of the file and make the Linux text file “executable”.
In our example, the file is named: listdirs
Below is a Linux chmod command example for running the chmod command to change the permissions of the Linux script file – and to make the listdirs text / script file “executable”, so that you can run the script file in the same way as you run a command.
The $ (dollar sign) below is the Linux command line prompt. Don’t type in the $ (dolar sign), type in the command that appears at the right of the $ prompt.
$ chmod u+x listdirs
The Linux command above is chmod and it is being used to assign the x (executable) permission to the u (user) of the file with: u+x and the script file name is listdirs.
Running a Linux Script to Run System Administration Commands
To run a Linux script (that is in the “current” directory), such as the listdirs script, simply type in a period (dot) and a space and then the name of the file and press Enter.
$ . listdirs
The concepts and Linux command examples shown above work in Red Hat, Ubuntu, Fedora, Slackware, and Debian Linux – and also ALL Linux distributions. Source: