touch — Create Files and Manipulate Timestamps | Sagar Kumar

touch has two main jobs:

Create empty files — if the file doesn't exist, touch creates it with zero bytes
Update timestamps — if the file already exists, touch updates its access and modification times to now

The name comes from its original purpose — "touching" a file to update its timestamp, signalling to build tools like make that the file has changed.

Options

touch Options

Option	Description
`-a`	Update access time only
`-m`	Update modification time only
`-c`	Don't create file if it doesn't exist
`-d STRING`	Set timestamp from human-readable string (e.g. `"2024-01-15 10:30"`)
`-t STAMP`	Set timestamp in `[[CC]YY]MMDDhhmm[.ss]` format
`-r FILE`	Copy timestamp from another file

Creating Files

touch file.txt               # Create empty file (or update timestamp)
touch file1.txt file2.txt    # Create multiple files at once
touch .hidden_file           # Hidden file (starts with .)

# Pro: combine with brace expansion
touch index.{html,css,js}   # Creates index.html, index.css, index.js
touch file{1..10}.txt        # file1.txt through file10.txt

Updating Timestamps

Every file in Linux has two timestamps:

Access time (atime) — last time the file was read
Modification time (mtime) — last time the file content was changed

By default, touch updates both. Use -a or -m to update only one.

touch file.txt               # Update both atime and mtime to now
touch -a file.txt            # Update access time only
touch -m file.txt            # Update modification time only
touch -c nonexistent.txt     # Update if exists, don't create if not

# Set a specific timestamp
touch -d "2024-06-15 09:30" report.txt
touch -t 202406150930 report.txt        # Same: YYYYMMDDhhmm

# Copy timestamp from another file
touch -r reference.txt target.txt       # target gets reference's time

Checking Timestamps

# See modification time
ls -l file.txt

# See both access and modification time
stat file.txt
# File: file.txt
# Size: 0               Blocks: 0          IO Block: 4096   regular empty file
# Access: 2025-01-11 10:30:00
# Modify: 2025-01-11 10:30:00
# Change: 2025-01-11 10:30:00

Quick Check

You run `touch existing.txt` on a file that already exists and has content. What happens?

Exercise

Create a set of test files using brace expansion: log-{jan,feb,mar}.txt and config.{yaml,json,toml}
Check their timestamps with ls -l
Wait a few seconds, then touch one file
Compare timestamps with ls -lt (sorted by time) to see which was touched most recently