Tee (command)

tee is a Unix command that displays the output of a program and copies it into a file.

Syntax

tee [ -a ] [ -i ] [ File ... ]

Description

The tee command reads standard input, writes its content to standard output and simultaneously copies it into the specified file or files.

Flags

• -a Adds the output to the end of File instead of writing over it.
• -i Ignores interrupts.

Exit Status

This command returns the following exit values:

• 0 The standard input was successfully copied to all output files.
• >0 An error occurred.

Note: If a write to any successfully opened File operand is not successful, writes to other successfully opened File operands and standard output will continue, but the exit value will be >0.

Examples

• To view and save the output from a command at the same time:

    lint program.c | tee program.lint

This displays the standard output of the command lint program.c at the workstation, and at the same time saves a copy of it in the file program.lint. If a file named program.lint already exists, it is deleted and replaced.

• To view and save the output from a command to an existing file:

    lint program.c | tee -a program.lint

This displays the standard output of the lint program.c command at the workstation and at the same time appends a copy of it to the end of the program.lint file. If the program.lint file does not exist, it is created.

• To allow escalation of permissions:

    echo "Body of file..." | sudo tee root_owned_file > /dev/null

This example shows tee being used to bypass an inherent limitation in the sudo command. sudo is unable to pipe the standard output to a file. By dumping its stdout stream into /dev/null, we also suppress the mirrored output in the console.

See also

• The script command
• List of Unix programs
• A good faq on Linux I/O Redirection "Linux I/O Redirection" with tee