103.4 Use streams, pipes and redirects

Question 1

What does the command xargs do?

Answer 1

It will take the stdout of one command and use it as stdin in another command as options, just like -exec but it is more efficient.

Question 2

What does the command xargs do?

Answer 2

It will take the stdout of one command and use it as stdin in another command as options, just like -exec but it is more efficient.

Question 3

What does the tee command do?

Answer 3

It redirects stdout from one command to a file while at the same time printing the stdout to the screen to be seen.

Question 4

What does this command do?
#ls -d /usr/share/doc/lib[Xx]* | tee lib.docs.txt

Answer 4

• It lists only directories within /usr/share/doc/lib
• The directories to be listed start with a capital or lowercase X
• The stdout gets written to the file lib.docs.txt while being printed on the screen.

Question 5

What symbol do you use to redirect stdout as stdin to a command?

Answer 5

pipe |

Question 6

How do you redirect stdin towards a command?

Question 7

What symbols do you use to append stdout to a file?

Answer 7

> >

Question 8

What does the tee command do?

Answer 8

It redirects stdout from one command to a file while at the same time printing the stdout to the screen to be seen.

Question 9

What does this command do?
#ls -d /usr/share/doc/lib[Xx]* | tee lib.docs.txt

Answer 9

• It lists only directories within /usr/share/doc/lib
• The directories to be listed start with a capital or lowercase X
• The stdout gets written to the file lib.docs.txt while being printed on the screen.

Question 10

What symbol do you use to redirect stdout as stdin to a command?

Answer 10

pipe |

Question 11

Give an example of standard output and standard input.

Answer 11

#wc test.sh   
# wc < test.sh
cat /etc/passwd | less

Question 12

What symbols do you use to append stdout to a file?

Answer 12

> >

Question 13

How do you redirect stdout and stdin of a script to the less command?

Answer 13

test.script 2>&1 | less

Question 14

Which are the file handles for stdout, stdin and stderr?

Answer 14

stdin < 0
stdout > 1
stderr : 2

Question 15

Where is stderr printed?

Answer 15

It is printed to the screen just like stdout

Question 16

How is standard error abbreviated?

Answer 16

Stderr

Question 17

Give an example of standard output and standard input.

Answer 17

#wc test.sh   
# wc < test.sh

Question 18

How is standard input abbreviated as?

stdin

Answer 18

What are the symbols used for stdin?

< and pipe ( | )

Question 19

Where does standard input come from?

Answer 19

It comes from the user’s input on the keyboard.

Also sodut of a command can be the stdin or another.

Question 20

What are the symbols used to redirect stdout?

Answer 20

> and&raquo_space;

Question 21

What is stdout?

Answer 21

It is whatever you see printed on the screen when you run a command.

Question 22

How is standard output abbreviated?

Answer 22

stdout

Question 23

How can you retrieve the process IDs that are related to a particular user?

Answer 23

psgrep -u