ps

ps $($process status$)$ is a tool that lists running processes. By default, it lists only your own

processes. Since we want to look at other users we will want to use at least the flag a $($ps

doesn$$t use $-$ for its options, so this would just be ps a$).$ We$$ll also want to know about

hidden processes, so need the x flag, and we need to get extra information so need the u

flag. The command you have will now give you a list of all processes and a lot of information

about them.

grep

grep allows us to search for a specific pattern. We can take the output of ps and pipe it to

grep to search for a pattern and return only lines with that pattern.

cut and tr

If we want to extract specific information from our ps output we can use cut which allows

you to specify a delimiter with $-$d we can then say which field we want with $-$f$.($you can

also use character ranges with $-$c$).$ For fields sometimes it$$s helpful to use tr to $-$s squash

delimiters together.

sort

We can sort a file or input using the sort command. You might need the $-$r flag to get the

order you want. You might also need the $-$h flag to sort numerically.

head

We can get just the first few items in a file or input using the head command. The $-$n flag

changes the number of lines.

Making MiniMon $[80$ Points$]$

Get RSS usage for a user

Using the above create a BASH script called minimon.sh$.$ In your script write a function

that takes a username as an argument, and then uses ps$,$ grep, tr$,$ and cut with pipes to

return the RSS $($resident memory$)$ that the user is consuming.

Combine RSS usage for a user

Write a second function that can take the output of the above and sum all the values.

$3$

Find largest RSS usage for a user

Write a third function that takes the output from the first and finds the largest single RSS

usage $($peak$).$

Combine RSS usage for a user

Finally, write the main body of your loop to use the above functions to compute the total

RSS and peak RSS for a user given as a parameter. The output must be printed as:

:

Where $,,$ and are replaced by the correct respective

values. Your log should follow exactly this format

Alerting $[20$ Points$]$

Extend your script to allow a third parameter which is the alerting threshold. This should

be compared to the total and peak RSS$.$ If either exceeds this value then a message should

be output on stderr. This message should have the following format:

ALERT: : exceeded RSS threshold $(<$##$>[$peak $|$ total$])$

Where $,$ is replaced by its correct respective value, $<$##$>$ is the peak or total

value that exceeded the threshold, and $[$peak $|$ total$]$ is replaced by either $$peak$$ or

$$total$$ depending on which caused the alert condition. Your alerts should follow exactly

this format To print to stderr we$$ll need to use a redirecting trick: $1>$&$21$

$1$This tells bash to redirect stdout $(1)$ to stderr $(2).$ It can also be used the otherway if you need errors

in output for your scripts i$.$e$.2>$&$1$