Linux2

Leveraging the power of the Linux command line

Getting the content for this practical

The necessary files for this practical are hosted in a version control system. To obtain them, just type the following command:

$ svn export http://source.ggy.bris.ac.uk/subversion-open/linux2/trunk linux2

This will fetch all necessary files and put them in a folder called linux2/. Ignore the cryptic syntax so far, an introduction to version control using subversion (svn) will be given later on.

Output redirection

In the Linux1 practical, we have discovered a few Linux commands. Some of these commands use input from the keyboard (standard input) and output data to the screen (standard output). It is possible to (a) redirect input and output and (b) link commands together to perform complex actions.

Redirecting standard input and output

The diff command outputs to the screen.

$ diff file1 file2

$ diff file1 file2 > diff12.txt
$ diff file2 file3 > diff23.txt

$ cat diff12.txt diff23.txt > diff.txt

$ diff file1 file2 > diff.txt
$ diff file2 file3 >> diff.txt

It is also possible to redirect the input. For instance consider the following

Pipelines

pipes between simple commands

ls -l | more

diff file1 file2 | tail

grep -i scene | wc

Automating things

"batch files"

Launching, monitoring and controlling jobs

Background, bg, jobs, fg, nohup, top, kill

Environment Variables

SHELL PWD PATH (LD_LIBRARY_PATH)

Uploaded example scripts for:

• Environment Variables
• Conditionals
• For loops
• Functions
• Arithmetic

Text Processing

sed, awk.