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→INVESTIGATION 3: USING CONTROL FLOW STATEMENTS IN SHELL SCRIPTS
# Issue the following linux command to test a condition involving numbers:<br><span style="color:blue;font-weight:bold;font-family:courier;">test $number1 > $number2</span><br><br>
# Issue a linux command to display the value of '''$?'''. '''NOTE:''' You will notice that something is '''wrong'''.<br>The exit status '''$?''' shows a zero (TRUE) value, but the number 5 is definitely NOT greater than 10.<br>The problem is that the symbols '''<''' and '''>''' are interpreted as REDIRECTION symbols!<br><br>
# To prove this, issue the following linux command :<br><span style="color:blue;font-weight:bold;font-family:courier;">ls 510</span><br><br>You should notice a file called "'''510'''". The incorrectly issued '''test''' command used redirect to create an empty file instead,<br> which indeed succeeded just giving a TRUE value!<br><br>To prevent these incorrectly issued testing for number comparison, you can use the following options instead:<br>'''-lt''' (<), '''-le''' (<=), '''-gt''' (>), '''-ge''' (>=;), '''-eq''' (=), '''-ne''' (!=)<br><br>
# Issue the correct linux command to properly test both values:<br><span style="color:blue;font-weight:bold;font-family:courier;">test $number1 -gt $number2</span><br><br>
# Issue a linux command to display the value of '''$?'''. You should notice that the exit status value is now FALSE which is the correct result.<br><br>