The Linux tee Command: Write Output to a File and stdout at the Same Time

Sat Aug 08 2026

What tee Does

tee sits in a pipeline, reads stdin, and writes it simultaneously to both stdout and one or more files. The name comes from a T-junction in plumbing: data flows in one side and splits into two identical streams. Without tee, redirecting with > would consume the stream and leave nothing for downstream commands.

flowchart LR
    stdin["stdin<br/>from pipe"] --> tee["tee"]
    tee --> stdout["stdout<br/>(terminal / next command)"]
    tee --> file["file<br/>(saved to disk)"]

Basic Syntax and the -a Flag

The minimal invocation is command | tee filename. By default tee overwrites the target file (like >). Add -a to append instead (like >>):

$ echo "first line" | tee log.txt
first line
$ echo "second line" | tee -a log.txt
second line
$ cat log.txt
first line
second line

Silencing stdout and Pipeline Use

tee always writes to stdout. To suppress it, redirect to /dev/null: command | tee file > /dev/null. The file is still written; the terminal stays quiet.

You can also place tee between two commands to save intermediate results while the pipeline continues, invaluable for debugging:

$ cat /etc/hostname | tee saved-hostname.txt | wc -c
5
$ cat saved-hostname.txt
arch

flowchart LR
    cat["cat /etc/hostname"] --> tee["tee saved-hostname.txt"]
    tee --> wc["wc -c"]
    tee --> file["saved-hostname.txt"]

Writing to Multiple Files and Common Pitfalls

tee accepts multiple filename arguments, writing identical copies to all of them: echo "server=localhost" | tee config-a.conf config-b.conf.

A common mistake is writing command | tee > file. The > redirect applies to tee’s stdout, not its file-writing behavior, tee with no filename just passes stdin through unchanged. The correct form is command | tee file.

When to Reach for tee

Three canonical use cases: (1) watching a long command’s progress while keeping a log; (2) debugging a multi-stage pipeline by inspecting intermediate data; (3) writing the same output to several files in one shot. If you only need the file and do not care about seeing output, plain > is simpler.