Basic Shell Scripting

This is a basic shell scripting tutorial i got off the Net. Credit goes to the writer. By the way, the site i ripped this off was at
http://more-shell.blogspot.com/2007/03/easy-shell-scripting.html


Easy Shell Scripting

By Blessen Cherian

Shell scripting can be defined as a group of commands executed in sequence. Let's start by describing the steps needed to write and execute a shell script:

Step 1: Open the file using an editor (e.g., "vi" or "pico".) vi Firstshellscript.sh

Step 2: All shell scripts should begin with "#!/bin/bash" or whatever other shell you prefer. This line is called the shebang, and although it looks like a comment, it's not: it notifies the shell of the interpreter to be used for the script. The provided path must be an absolute one (you can't just use "bash", for example), and the shebang must be located on the first line of the script without any preceding space.

Step 3: Write the code that you want to develop. Our first shell script will be the usual "Hello World" routine, which we'll place in a file called 'Firstshellscript.sh'.

#!/bin/sh
echo "Hello World"

Step 4:The next step is to make the script executable by using the "chmod" command.

chmod 744 Firstshellscript.sh
or chmod +x Firstshellscript.sh

Step 5: Execute the script. This can be done by entering the name of the script on the command line, preceded by its path. If it's in the current directory, this is very simple:

bash$ ./Firstshellscript.sh
Hello World

If you want to see the execution step-by-step - which is very useful for troubleshooting - then execute it with the '-x' ('expand arguments') option:

sh -x Firstshellscript.sh
+ echo 'Hello World'
Hello World

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