# NSCI 580A4 fall 2017

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NSCI 580A4

Instructors
Tai Montgomery
Erin Nishimura

wiki:2016chaining

# CHAINING AND SCRIPTING

## Chaining with ;

So far, we've typically executed one command per line. However, we learned to pipe commands together, which is a way of combining two commands into one.

We can also tell the shell to execute two commands in succession. This is called chaining and it uses the ;, semi-colon.

chaining usage:
command1; command2

Exercise: Try it:

$mkdir testdir; touch testfile.txt The shell waits for the first command to finish before the second command completes. You can command multiple commands together. ## Basic scripting We can also write very basic scripts by adding lists of commands into a script. Exercise: Copy and paste the following text into a script and name it testscript.sh: #!/bin/bash #make a directory mkdir scriptdir #make a readmefile touch readmefile.txt Execute the command by returning to the command prompt and executing:$ bash testscript.sh

Alternatively, you can make your script executable with the chmod command (change mode). Once it is executable, you can execute it with ./testscript.sh

$chmod 744 testscript.sh$ ./testscript.sh

Learn more on your own: We'll cover more about permissions later in the class. You can learn more about permissions and chmod on your own here Permissions

Common pitfall: Comment your code!!! This makes your code readable to other users. Remember other user is you, 2 months from now.

Common pitfall: Test your scripts frequently for proper behavior. Even the best programmers test their code every few lines.

wiki/2016chaining.txt · Last modified: 2017/08/29 09:00 by erin