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tee Cheatsheet

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Basic Syntax

Core tee command forms.

Command Description
command | tee file.txt Show output and write to a file
command | tee -a file.txt Show output and append to a file
command | tee file1.txt file2.txt Write output to multiple files
command | tee Pass output through unchanged
command | tee /tmp/out.log >/dev/null Write to file without terminal output

Common Options

Frequently used flags for tee.

Option Description
-a, --append Append to files instead of overwriting
-i, --ignore-interrupts Ignore interrupt signals
--help Show help text
--version Show version information

Logging Command Output

Capture output while still seeing it live.

Command Description
ping -c 4 linuxize.com | tee ping.log Save ping output to a log file
journalctl -u nginx -n 50 | tee nginx.log Save recent service logs
ls -la | tee listing.txt Save directory listing
df -h | tee disk-usage.txt Save filesystem usage report
free -h | tee memory.txt Save memory snapshot

Append Mode

Keep history in log files with -a.

Command Description
date | tee -a run.log Append current date to log
echo "deploy started" | tee -a deploy.log Append status line
./backup.sh 2>&1 | tee -a backup.log Append stdout and stderr
tail -n 20 app.log | tee -a diagnostics.log Append recent log excerpt
curl -I https://linuxize.com | tee -a headers.log Append response headers

Pipelines and Filters

Combine tee with text-processing commands.

Command Description
cat app.log | tee copy.log | grep ERROR Copy stream and filter errors
ps aux | tee processes.txt | grep nginx Save process list and filter
sort users.txt | tee sorted-users.txt | uniq Save sorted output and deduplicate
dmesg | tee dmesg.txt | tail -n 30 Save kernel messages and inspect recent lines
find /etc -maxdepth 1 -type f | tee etc-files.txt | wc -l Save file list and count lines

Privileged Writes

Write to root-owned files safely.

Command Description
echo "127.0.0.1 app.local" | sudo tee -a /etc/hosts Append host mapping as root
printf "key=valuen" | sudo tee /etc/myapp.conf >/dev/null Overwrite config file as root
cat config.conf | sudo tee /etc/myapp/config.conf >/dev/null Copy config into protected path
echo "net.ipv4.ip_forward=1" | sudo tee -a /etc/sysctl.conf Append kernel setting
sudo sysctl -p | tee sysctl-apply.log Save reload output

Troubleshooting

Quick checks for common tee issues.

Issue Check
Permission denied Use sudo tee for root-owned targets instead of sudo echo ... > file
File content replaced unexpectedly Use -a when you need append mode
No output on terminal Remove >/dev/null if you want to see output
Missing errors in logs Redirect stderr too: 2>&1 | tee file.log
Command hangs in pipeline Check whether the upstream command runs continuously and needs manual stop

Related Guides

Use these guides for deeper command coverage and workflow patterns.

Guide Description
tee Command in Linux Full tee command tutorial
grep Command in Linux Filter matching lines
sort Command in Linux Sort text output
tail Command in Linux Inspect and follow recent lines
head Command in Linux Show first lines quickly
journalctl Command in Linux Query and filter systemd logs
Bash Append to File Append redirection patterns