Cheatsheet & Examples: tee

Basic Usage: Output to a File

Example Usage:
tee filename

What it does:
Writes the standard output to the specified file. If the file doesn’t exist, it creates it. If it does, it appends to it.

Command-line Arguments Explained:

• filename: The name of the file to write to. It must be specified.

Redirecting Output While Running a Command

Example Usage:
command | tee filename

What it does:
Redirects the output of the command to the specified file. The command continues to run, and its output is written to the file.

Command-line Arguments Explained:

• filename: The name of the file to write to. This is the same as in the first example.

Redirecting Both stdout and stderr

Example Usage:
command 2>&1 | tee filename

What it does:
Redirects both standard error and standard output of the command to the specified file. The command continues to run, and its output is written to the file.

Command-line Arguments Explained:

• filename: The name of the file to write to. This is the same as in the first example.

Appending to a File

Example Usage:
tee -a filename

What it does:
Appends the standard output to the specified file. If the file doesn’t exist, it creates it. If it does, it adds the output to the end of the file.

Command-line Arguments Explained:

• -a: Appends to the file instead of overwriting it. This option is used to avoid overwriting existing content.

Using with Other Commands

Example Usage:
cat | tee filename

What it does:
Redirects the output of cat to the specified file. The cat command outputs the file's contents to stdout, which is then written to the file.

Command-line Arguments Explained:

• filename: The name of the file to write to. This is the same as in the first example.

Other Options

Example Usage:
tee -n filename

What it does:
Prevents tee from overwriting the file if it already exists. This is useful when you want to append to the file without overwriting.

Command-line Arguments Explained:

• -n: Prevents tee from overwriting the file if it already exists.

Using with Multiple Outputs

Example Usage:
tee -a log.txt | grep "error" | tee error.log

What it does:
Redirects output from tee to log.txt and then filters it with grep before writing to error.log.

Command-line Arguments Explained:

• log.txt: The file to write to initially.
• error.log: The file to write to after filtering.
• -a: Appends to log.txt instead of overwriting it.

Using with &>

Example Usage:
command &> tee filename

What it does:
Redirects both standard output and standard error to the specified file.

Command-line Arguments Explained:

• filename: The name of the file to write to. This is the same as in the first example.