Command Line: Pipes and Redirection

Question 1

Send output of a command to a file named myoutput and keep the myoutput contents

Answer 1

ls&raquo_space; myoutput

will append the output of ls command to the file named myoutput

Question 2

Send output of a command to a file named myoutput and overwrite contents

Answer 2

ls > myoutput

will overwrite the contents of the myoutput file and replace it with the current directory list

Question 3

Read contents of a file to the terminal

Answer 3

cat filename.txt

Question 4

Count words of a file

Answer 4

wc

Question 5

Count lines of a file

Answer 5

wc -l

Question 6

Output errors of a command to a file

Answer 6

… 2> errorfileName.txt

For example if fakeFile.txt does not exist the following command will send the error the errors.txt
ls realFile.txt fakeFile.txt 2> errors.txt

Question 7

limit the output of a command to the first 4 items

Answer 7

command | head -4
for example: ls | head -4
will only show the first for filesystem items
pipes can be chained so we could: ls | head -4 | head -2 which will only show the 3rd and 4th items

Question 8

Command line operator uses the same file for input and output

Answer 8

<>