Which of the following will take output from a command and append it to the end of a file?

Cat(concatenate) command is very frequently used in Linux. It reads data from the file and gives their content as output. It helps us to create, view, concatenate files. So let us see some frequently used cat commands. 

1) To view a single file 
Command: 
 

$cat filename

Output 
 

It will show content of given filename

2) To view multiple files 
Command: 
 

$cat file1 file2

Output 
 

This will show the content of file1 and file2.

3) To view contents of a file preceding with line numbers. 
Command: 
 

$cat -n filename

Output 
 

It will show content with line number
example:-cat-n  geeks.txt
1)This is geeks
2)A unique array

4) Create a file 
Command: 
 

$ cat > newfile

Output 
 

Will create a file named newfile

5) Copy the contents of one file to another file. 
Command: 
 

$cat [filename-whose-contents-is-to-be-copied] > [destination-filename]

Output 
 

The content will be copied in destination file

6) Cat command can suppress repeated empty lines in output 
Command: 
 

$cat -s geeks.txt

Output 
 

Will suppress repeated empty lines in output

7) Cat command can append the contents of one file to the end of another file. 
Command: 
 

$cat file1 >> file2

Output 
 

Will append the contents of one file to the end of another file

8) Cat command can display content in reverse order using tac command. 
Command: 
 

 $tac filename

Output 
 

Will display content in reverse order 

9) Cat command can highlight the end of line. 
Command: 
 

$cat -E "filename"

Output 
 

Will highlight the end of line

10) If you want to use the -v, -E and -T option together, then instead of writing -vET in the command, you can just use the -A command line option. 
Command 
 

$cat -A  "filename"

11) Cat command to open dashed files. 
Command: 
 

$cat -- "-dashfile"

Output 
 

Will display the content of -dashfile

12) Cat command if the file has a lot of content and can’t fit in the terminal. 
Command: 
 

$cat "filename" | more

Output 
 

Will show that much content, which could fit in terminal and will ask to show more.

13) Cat command to merge the contents of multiple files. 
Command: 
 

$cat "filename1" "filename2" "filename3" > "merged_filename"

Output 
 

Will merge the contents of file in respective order and will insert that content in "merged_filename".

14) Cat command to display the content of all text files in the folder. 
Command: 
 

$cat *.txt

Output 
 

Will show the content of all text files present in the folder.

15) Cat command to write in an already existing file. 

Command :

$cat >> geeks.txt
The newly added text.

Output

Will append the text "The newly added text." to the end of the file.

?list=PLqM7alHXFySFc4KtwEZTANgmyJm3NqS_L 

This article is contributed by Pranav. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to . See your article appearing on the GeeksforGeeks main page and help other Geeks. 

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

Introduction

When the user executes a command in a Linux interactive shell, the output displays in the text terminal. However, there are ways to change this behavior using additional shell commands connected in a pipeline.

In this tutorial, you will learn how to use the tee command in Linux to manage the output of a command.

Prerequisites

• A system running Linux
• Access to the command line or terminal
• Sudo privileges

What Does tee Command Do in Linux?

The tee command reads standard input (stdin) and writes it to both standard output (stdout) and one or more files. tee is usually part of a pipeline, and any number of commands can precede or follow it.

Note: To process standard inputs in Linux, you can use the xargs command which can be used in combination with other commands.

tee Commands in Linux With Examples

The tee command is used alone or with additional options. The following sections list the available options and provide command usage examples.

Basic Use

The basic syntax for the tee command is:

[command] | tee [options] [filename]

The example below demonstrates the use of tee to create a file that stores information about a network interface while providing the same output in the terminal:

The cat command confirms that tee successfully wrote the output of ifconfig to the file example.txt:

If the file used for the command already exists, tee overwrites the previous contents of the file.

Append to the Given File

Overwriting the file’s content is the default behavior of the tee command. Use argument -a (or --append) to add the command output to the end of the file.

[command] | tee -a [filename]

For example, use the echo command to append a line of text to a file:

Confirm the successful addition with the cat command:

Write to Multiple Files

Use tee followed by any number of files to write the same output to each of them:

[command] | tee [options] [filename1] [filename2]...

The example below shows writing the output of the echo command to two files:

The ls command shows that tee successfully created files example1.txt and example2.txt.

Hide the Output

To tell tee to store the command output in a file and skip the terminal output, use the following syntax:

[command] | tee [options] [filename] >/dev/null

In the example bellow, tee creates a file containing the network interface data, skipping the standard output:

Redirect Output of One Command to Another

tee does not have to be the last command in the pipeline. Use it to forward the output to another command:

[command] | tee [options] [filename] | [command]

In the following example, tee stores the output of the ls command to example.txt and passes the content of that file to the grep command, which finds and displays all instances of the word “example”:

Ignore Interrupts

To enable tee to exit properly even after the previous command has been interrupted, add the argument -i (or --ignore-interrupts):

[command] | tee -i [filename]

The next example shows tee writing output from the ping command and completing the action successfully even after ping is interrupted with Ctrl+C:

Using tee with Sudo

To enable tee to write to a root-owned file or file belonging to another user, place the sudo command right before tee.

[command] | sudo tee [options] [filename]

The example below shows an unsuccessful attempt to write to the root-owned sudoex.txt. When the sudo command is added, the operation completes:

Using tee in Vim Editor

If you open and edit a root-owned file in Vim without using the sudo command, trying to save changes produces an error:

To override this error, type the following into Vim:

:w !sudo tee %

After you enter the sudo password, Vim displays a warning but writes the changes to the file.

Diagnose Errors Writing to Non-Pipes

To instruct tee to print an error message when the process fails, use the -p argument:

[command] | tee -p [filename]

The default action of tee -p is to exit and print the error message immediately upon detecting the error writing to a pipe. To change the command’s behavior on write error, use the --output-error argument, followed by the mode specifying the behavior:

[command] | tee --output-error=[mode] [filename]

There are four possible modes:

• warn – diagnoses errors writing to any output.
• warn-nopipe – diagnoses errors writing to any non-pipe output.
• exit – exits on errors writing to any output.
• exit-nopipe – exits on errors writing to any non-pipe output.

Use tee Command with Bash Script

The tee command is often found in bash scripts. Consider the following example:

The script above prints the “Hello World” message and stores the output in a log file. Executing the script creates a log file in the tmp folder. The log contains the output of the script:

Watch Log Files

Writing script output to a log file is usually performed with the >operator:

./testbash.sh > testbash.log

The command above creates a log file but does not write anything to standard output.

Use tee to create a log file and see the output in the terminal:

./testbash.sh | tee testbash.log

See Help and Version Information

See the current version of the tee command by typing:

tee --version

For the instructions regarding the tee command syntax and the available arguments, use the command’s help argument:

tee --help

Conclusion

By reading this tutorial, you learned how to use the tee command in a pipeline to manage the command output. The article also talked about the use of tee in bash scripts.

Read more about shell commands in this Linux commands cheat sheet.

Which of the following commands will display the exit status of the last command used in the bash shell a echo $status B echo $Exit C echo $? D echo $!?

Which of the following will the Split command do on a file?

Which of the following commands will count the number of lines in a file named?

Which of the following is a type of software that allows a piece of hardware to host multiple operating systems?