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→INVESTIGATION 4: CONTROL FLOW STATEMENTS
# Save your editing session and exit the text editor (eg. with vi: press '''ESC''', then type ''':wx''' followed by '''ENTER''').<br><br>[[Image:if-3.png|thumb|right|330px|Output of a shell script using the '''if-else''' control-flow statement.]]
# Issue the following Linux command to add execute permissions for your shell script:<br><span style="color:blue;font-weight:bold;font-family:courier;">chmod u+x if-3.bash</span><br><br>
# Run your shell script by issuing:<br><span style="color:blue;font-weight:bold;font-family:courier;">./if-3.bash</span><br><br>Try running the script several times with numbers '''different''' and '''equal''' to each other to confirm that the shell script works correctly.<br><br>Let's learn how to use a '''loop''' with shell scripting. In this tutorial, we will only focus on one simple use with the '''for''' loop.<br><br>'''LOOP STATEMENTS'''<br><br>''A <b>loop statement</b> is a series of steps or sequence of statements executed repeatedly<br>zero or more times satisfying the given condition is satisfied.''<br>Reference: https://www.chegg.com/homework-help/definitions/loop-statement-3<br><br>There are several loops, but we will look at a '''for''' loop using a '''list'''.<br><br>
# Use a text editor like vi or nano to create the text file called '''for-1.bash''' (eg. <span style="color:blue;font-weight:bold;font-family:courier;">vi for-1.bash</span>)<br><br>
# Enter the following lines in your shell script:<br><span style="font-family:courier;font-weight:bold;">#!/bin/bash<br>echo<br>for x in 5 4 3 2 1<br>do<br> echo $x<br>done<br>echo "blast-off!"<br>echo</span><br><br>