10 tee command examples in Linux [Cheat Sheet]

Introduction to tee command in Linux

tee command reads from standard input (stdin) and writes to standard output (stdout) and files. tee is mainly used with other commands through piping.

 

Syntax to use tee command

The syntax of the tee command is:

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$ tee [option] [file]

The available options are:

  • -a: append to the given FILEs, do not overwrite
  • -i: ignore interrupt signals
  • --help: display help menu

Now, let's have a look at some practical examples in a Linux system.

 

Different examples to use tee command

1. tee command to append to the file

-a or --append option appends to the file but does not overwrite the file. It adds the content to the end of a file.

$ tee -a file

OR

$ tee --append file

Sample Output:

tee command to append to the given files

 

2. Use tee command to append content to multiple files

You can also append to the multiple files using -a or --append option.

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$ tee -a file1 file2 file3

OR

$ tee --append file1 file2 file3

Sample Output:

tee command to append to the multiple files

 

3. Combine tee command with other commands

You can combine tee command with other commands through pipe (|). For example, we can combine grep and tee command as follows.

$ grep nu system.txt | tee -a file1.txt

Sample Output:

Here, tee command reads input from grep and writes to the output file. When -a is not used, tee overwrites the file.

combine tee command with other commands

 

4. tee command to ignore interrupts

You can use -i or --ignore-interrupts to ignore interrupts signal, which is done by pressing Ctrl+C.

$ tee -i file

OR

$ tee --ignote-interrupts file 

Sample Output:

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tee command to ignore interrupts signal

 

5. Supress the output from tee command

You can use >/dev/null to hide the standard output. tee stores the content but skips the output.

$ command | tee file >/dev/null 

Sample Output:

As you can see, it does not display the standard output but the content is stored in the file.

tee command to hide the output

 

6. Redirect output of one command to another

tee can redirect the output of one command to another command when it is used between two commands like below.

$ command | tee [option] file | command

Sample Output:

Here, the output of ipcs -c command is stored by tee in file and passes to the grep command to complete the action.

tee command to redirect output of one command to another

 

7. Using tee command with sudo

You need to use sudo before tee command to enable write access to root-owned files and files owned by another user. Or, you can also log in as a root user.

[command] | sudo tee file  

Sample Output:

Without root permission, tee cannot write to root-owned files and files owned by other users.

using tee command with sudo

 

8. Diagnose errors by writing to non pipes

-p option tells tee to diagnose errors writing to non-pipes.

$ [command] | tee -p file

The default action of -p command is to exit and print an error message after diagnosing the error writing to a pipe. You can change this behavior using --output-error[=MODE] option.

[command] | tee --output-error[=MODE] file

MODE determines behavior with write errors on the outputs:
warn: diagnose errors writing to any output
warn-nopipe: diagnose errors writing to any output not a pipe
exit: exit on error writing to any output
exit-nopipe: exit on error writing to any output not a pipe

The default MODE for the -p option is warn-nopipe.

 

9. Display the version

You can use --version option to print the version of tee installed in the system.

$ tee --version

Sample Output:

tee command to display the version

 

10. Display help menu

You can view the syntax and available options of tee command using --help option.

$ tee --help

Sample Output:

ubuntu@golinux:~$ tee --help
Usage: tee [OPTION]... [FILE]...
Copy standard input to each FILE, and also to standard output.

  -a, --append              append to the given FILEs, do not overwrite
  -i, --ignore-interrupts   ignore interrupt signals
  -p                        diagnose errors writing to non pipes
      --output-error[=MODE]   set behavior on write error.  See MODE below
      --help     display this help and exit
      --version  output version information and exit

MODE determines behavior with write errors on the outputs:
  'warn'         diagnose errors writing to any output
  'warn-nopipe'  diagnose errors writing to any output not a pipe
  'exit'         exit on error writing to any output
  'exit-nopipe'  exit on error writing to any output not a pipe
The default MODE for the -p option is 'warn-nopipe'.
The default operation when --output-error is not specified, is to
exit immediately on error writing to a pipe, and diagnose errors
writing to non pipe outputs.

GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
Full documentation at: <https://www.gnu.org/software/coreutils/tee>
or available locally via: info '(coreutils) tee invocation'

 

Conclusion

tee is a helpful command that copies standard input to files and standard output. We hope you have learned tee command and its usage from this article. If you still have any confusion, feel free to ask us in the comment section.

 

What's Next

20 grep command examples in Linux [Cheat Sheet]

 

Further Reading

man page for tee command

 

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