Shell Scripting / Bash Tricks

Stop running commands blind, log and watch at the same time

🧩 The Challenge

Ever kick off a long process, but you *really* need to see the output scrolling by? And then you realize you also want that output saved to a file for later review? You’ve probably run it once to screen, then again redirected to a file, or tried some clunky `script` command dance. What a waste of time.

💡 The Fix

There’s this simple command that lets you do both: pipe your output to `tee`. It’ll print everything to your terminal AND dump it into a file, all in one go. Saves you from rerunning stuff or getting lost in temporary files.

# Run a command, see its output, and save it to a file
my_long_running_command --verbose | tee my_output.log

# Append to the log file instead of overwriting
my_other_command | tee -a my_output.log

# Log both stdout and stderr (bash specific)
my_noisy_command &> >(tee my_noisy_output.log)

⚙️ Why It Works

The `tee` command gets its name because it works like a T-splitter in plumbing, sending its standard input to both standard output and to one or more files. Using `tee -a` tells it to append to the log file instead of overwriting, which is handy. For capturing both stdout and stderr, we’re sending both streams (`&>`) into a process substitution `>(…)` where `tee` then handles the combined output.

🚀 Pro-Tip: Pair this with `pv` for a progress bar on really big files before `tee` if you’re feeling fancy.

Linux Tips & Tricks | © ngelinux.com | 9/24/2026