Command Line Tools

Question 1

The echo command is an internal command in bash (true or False)

Answer 1

True

Question 2

You type “echo $PROC” and the computer replies “go away”. What does this mean?

Answer 2

The $PROC environment variable is set “Go away”.

Question 3

What does the pwd command accomplish?

Answer 3

It prints the name of the working directory

Question 4

In an xterm window launched from your window manager, you type exec gedit. What will happen when you exit from the gedit program?

Answer 4

The xterm window will close.

Question 5

What is the surest way to run a program (say, myprog) that’s located in the current working directory?

Answer 5

Type ./ followed by the program name: ./myprog

Question 6

How does man display information by default on most Linux?

Answer 6

Using the less pager

Question 7

You want to store the standard output of the ifconfig command in a text file (file.txt) for future reference, and you want to wipe out any existing data in the file. You do not want to store standard error in this file. How can you accomplish these goals?

Answer 7

Type: ifconfig > file.txt

Question 8

What is the effect of the following command?

$ myprog &> input.txt

Answer 8

Standard output and standard error from myprog are written to input.txt

Question 9

How many commands can you pipe together at once?

Answer 9

An arbitrary number (in most cases, 16 may be a reasonable number.

Question 10

You want to run an interactive script, gabby, which produces a lot of output in response to the user’s inputs. To facilitate future study of this script, you want to copy its output to a file. How might you do this?

Answer 10

Type: gabby | tee gabby-out.txt

Question 11

A text-mode program, verbose, prints a lot of spurious “error” messages to standard error. How might you get rid of those messages while still interacting with the program?

Answer 11

Type: verbose 2> /dev/null

Question 12

How do the > and&raquo_space; redirection operator differ?

Answer 12

The > operator creates a new file or overwrites an existing on; the&raquo_space; operator creates a new file or appends to an existing one.

Question 13

What program would you use to display the end of a configuration file?

Answer 13

The tail command displays the last 10 line of a file.

Question 14

What is the effect of the following command?

$ pr report.txt | lpr

Answer 14

The file report.txt is formatted for printing and sent to the lpr program.

Question 15

What commands will number the lines in aleph.txt?

Answer 15

1) nl aleph.txt
2) cat -b aleph.txt
3) cat -n aleph.txt

Question 16

What command will change all occurrences of dog in the file animals.txt to mutt in the screen display?

Answer 16

Type: sed ‘s/dog/mutt/g’ animals.txt

Question 17

You type a command into bash and pass a long filename to it, but after you enter the command, you receive a File not found error message because of a typo in the filename. What is the best course of action?

Answer 17

Press the Up arrow key, and use bash’s editing features to correct the typo.