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Tutorial10: Shell Scripting - Part 1

374 bytes removed, 17:39, 17 February 2021
INVESTIGATION 2: USING VARIABLES IN SHELL SCRIPTS
# Add the following line to the bottom of the file:<br><span style="font-family:courier;">ps -o cmd= -p $$|cut -d" " -f1</span><br><br>'''NOTE:''' This command displays the '''name''' of the ''shell'' that the shell script<br>is running within.<br><br>
# '''Save''' your editing changes and '''exit''' your text editor.<br><br>
# Issue the following linux command to run this shell script with the Bourne Shell (i.e. '''sh'''):<br><span style="color:blue;font-weight:bold;font-family:courier;">sh hello</span><br><br>You should see the output of the command that you are located in shows '''sh''' (i.e. the '''Bourne Shell''').<br><br>'''NOTE:''' Due to the fact that shells (and their features) have '''evolved''' over a period of time,<br>an error may occur if you include a ''NEWER'' shell feature (e.g. ''Bash Shell'') in your shell script,<br>but run it in an ''OLDER'' shell (e.g. ''Bourne Shell'').<br><br># While in the You can add a '''special comment'Bourne Shell'', run your shell script: <span style="color:blue;font-weight:bold;font-family:courier;">./hello</span><br><br>What shell does to the shell script indicate is running?<br>You should notice that this script is being run in BEGINNING of the Bourne shell.<br><br>Although FIRST line of your shell script should work, it is recommended to force your shell script it to run in a '''specific''' shell.<br>This helps prevent your shell script encountering errors when run in the incorrect shell<br>you want (i.e. syntax not recognized in a specific for example: the Bash shell).<br><br>
# Edit your '''hello''' shell script using a text editor.<br><br>
# Insert the following line at the '''beginning''' of the '''first''' line of your hello file:<br><span style="font-family:courier;">#!/bin/bash</span><br><br>This is referred to as a '''she-bang line'''. It forces the script to be run in the '''Bash Shell'''.<br>When your Bash Shell script finishes execution, you are returned to your current shell that you are using<br>(which in our case in Matrix, is still the Bash shell).<br><br>
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