Shell command: tee

Options

`-a`	`--append`	append to the given FILEs (i. e. do not overwrite)
`-i`	`--ignore-interrupts`	ignore interrupt signals
`-p`		diagnose errors writing to non pipes
	`--output-error[=MODE]`	set behavior on write error. If `--output-error` is not specified, `tee` will exit immediately on error writing to a pipe, and diagnose errors writing to non pipe outputs.
	`--help`
	`--version`	output version information and exit

MODE

The value of MODE determines the behavior with write errors on the output:

`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.

Using tee in combination with sudo

tee can be used in combination with sudo to create text-files owned by root in a variation of the following pipeline.

$ echo 'text text text' | sudo tee /etc/some-config-file

$PIPESTATUS

cmd-bad

cmd-bad is a shell script that write some text to stdout and more text to stderr.

It exits with code 42.

#!/bin/bash

>&1 echo "cmd-bad is running"
>&2 echo "cmd-bad is failing"
exit 42

Github repository shell-commands, path: /tee/cmd-bad

teeing output of cmd-bad

The following example shows how the output both to stdout and stderror can be captured and written to a file while at the same time writing it also to the console.

Additionally, the variable $PIPESTATUS is used to query the exit status of the command (rather than tee's exit status.

#!/bin/bash

cmd-bad 2>&1 | tee cmd-bad.log
echo "\$PIPESTATUS = $PIPESTATUS / \$? = $?"

Github repository shell-commands, path: /tee/PIPESTATUS