You may work in pairs, if space demands.                 
The purpose of this assignment is to get more experience writing Linux
scripts using bash
and other commands. You will create and edit a
bash script called pwval
that uses many of the features of shell
scripts described in the lecture.
                
The following commands might be useful for this lab:
Also, remember what $#
means in a shell script.
                
Lines in /etc/passwd
looks like this:
                
root:x:0:0:root:/root:/bin/bash applin:$6$30CrCh90r7Dl5Q4o$uwOkdKHjNkdBLIpreE090Cxt5z0WB765SLXry1QFE8n9fuwYrikKjY37kkPasFwf5My/w2HKgD6kdPsLT0hYV.:2464:1555:Jack Applin:/s/parsons/d/fac/applin:/bin/bash
The fields, separated by colons, are:                 
You will write a bash
script called pwval
that ensures
that /etc/passwd
is good. It will:
                
/etc/passwd
/etc/group
If an argument is given, then it is a file to be used instead
of /etc/passwd
. This is useful for testing.
                
Think of this program as something to be executed every day, from cron
.
Therefore, it should be relatively quiet. It shouldn’t say anything,
unless bad things are detected.
                
However, when the script does emit an error message, it must contain sufficient information to track down the problem. For example, an error message that simply says “duplicate user name” is insufficient—the message must specify, at least, what the duplicate user name is. Line numbers would be even better.                 
All error messages must:
/etc/passwd
)
that is being processed
$0
, so that it’s clear where the messages are coming from
echo "this is going to standard error" >&2
To get a temporary file, use mktemp to generate a unique name:
#! /bin/bash tmpfile=$(mktemp) echo "My temp file is $tmpfile" date >$tmpfile cat $tmpfile rm $tmpfile
My temp file is /tmp/tmp.NBjWd36TGi Fri Sep 6 07:19:44 MDT 2024
When you have tested your script, and it works, show your work to the TA.                 
User: Guest