tee Tee Command

Overview

The tee command copies standard input to standard output and to each specified file. It is useful in scripts or command pipelines when output needs to be displayed and saved at the same time.

When no files are specified, tee copies standard input to standard output only.

Configuration

Enable the application with CONFIG_SYSTEM_TEE.

The task priority and stack size are controlled by:

• CONFIG_SYSTEM_TEE_PRIORITY

• CONFIG_SYSTEM_TEE_STACKSIZE

Usage

tee [-a] [file ...]
tee -h

Options

Option	Description
-a	Append to each output file instead of truncating it.
-h	Show command usage and exit.

Arguments

file

Optional output file. Any number of files may be specified. Output is written to standard output in addition to each named file.

Examples

Copy input to standard output and save it in output.txt:

nsh> echo "hello" | tee output.txt
hello

Append input to an existing log file while also displaying it:

nsh> echo "next line" | tee -a log.txt
next line

Copy input to more than one file:

nsh> echo "sample" | tee first.txt second.txt
sample

Notes

The command opens each named file for writing. Without -a, existing files are truncated; with -a, output is appended. Files that do not already exist are created with mode 0644.

If opening an output file, reading from standard input, or writing to an output destination fails, the command exits with failure status.