Question

Exercise.

Practice redirection to change the above commands so that:

(i) error messages are sent to /dev/null, but

(ii) we still detect errors and halt execution of the sequence appropriately.

For i, recall from prior labs that standard error stream (stderr) is #2, and you will need redirection to route an error normally to stderr to /dev/null.

Hint: Recall that redirection happens per process executed. So, what do you need to add to each process to make the redirection successful?

Below are 4 commands to rewrite:

#1) ls . && ls -! && ls -al || echo "We Failed" #2) ls -! && ls . && ls -al || echo “We Failed” #3) ls . && ls -al && ls -! || echo "We Failed" #4) ls . && ls -al || echo “We Failed”

Write a new version of each by copying the list below, and add your revisions to the four above commands:

1.

2.

3.

4.

Answer 1

## Hey bud, here are your commands and explaination. Feel free to ask any doubt. Consider giving a thumbs up. ThankYou :)

# The standard error descriptor is 2.

# To pipe any error to /dev/null we use 2>/dev/null

# If there are multiple statements, then 2>/dev/null has to be used for each one of them

# Or better way to do it is listed below.

# Edited Commands ( Normal Way)

ls . 2>/dev/null && ls -! 2>/dev/null && ls -al 2>/dev/null || echo "We Failed"

ls -! 2>/dev/null && ls . 2>/dev/null  && ls -al 2>/dev/null || echo “We Failed”

ls . 2>/dev/null && ls -al 2>/dev/null && ls -! 2>/dev/null || echo "We Failed"

ls . 2>/dev/null && ls -al  2>/dev/null || echo “We Failed”

# Edited Commands (More Efficient Way)

{ ls . && ls -! && ls -al } 2>/dev/null || echo "We Failed"

{ ls -! && ls . && ls -al } 2>/dev/null || echo “We Failed”

{ ls . && ls -al && ls -! } 2>/dev/null || echo "We Failed"

{ ls . && ls -al } 2>/dev/null || echo “We Failed”