Quick Start Guide

18.7.1 The if Control Command
The if command is used to check expressions. For example, the following code tests
whether the current user is Tux:
if test $USER = "tux"; then
echo "Hello Tux."
else
echo "You are not Tux."
fi
The test expression can be as complex or simple as possible. The following expression
checks if the le foo.txt exists:
if test -e /tmp/foo.txt ; then
echo "Found foo.txt"
fi
The test expression can also be abbreviated in angled brackets:
if [ -e /tmp/foo.txt ] ; then
echo "Found foo.txt"
fi
Find more useful expressions at http://www.cyberciti.biz/nixcraft/linux/docs/
uniqlinuxfeatures/lsst/ch03sec02.html.
18.7.2 Creating Loops With the For Command
The for loop allows you to execute commands to a list of entries. For example, the
following code prints some information about PNG les in the current directory:
for i in *.png; do
ls -l $i
done
18.8 For More Information
Important information about Bash is provided in the man pages man bash. More about
this topic can be found in the following list:
•
http://tldp.org/LDP/Bash-Beginners-Guide/html/index.html—Bash Guide for
Beginners
•
http://tldp.org/HOWTO/Bash-Prog-Intro-HOWTO.html—BASH Programming - In-
troduction HOW-TO
•
http://tldp.org/LDP/abs/html/index.html—Advanced Bash-Scripting Guide
•
http://www.grymoire.com/Unix/Sh.html—Sh - the Bourne Shell
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