less — Linux command line pager — garron.me

What is less

less is a terminal pager — it lets you read files or command output one screen at a time, moving freely forward and backward. Unlike cat, it does not dump the entire file at once, which makes it ideal for large files and long outputs.

Basic usage

less filename
less /var/log/syslog
command | less

You can also open multiple files at once:

less file1.txt file2.txt

Use :n to go to the next file and :p to go back to the previous one.

Navigation

Key	Action
`Space` / `f`	Forward one page
`b`	Backward one page
`d`	Forward half a page
`u`	Backward half a page
`j` / `↓`	Forward one line
`k` / `↑`	Backward one line
`g`	Go to first line
`G`	Go to last line
`q`	Quit

Searching

Search forward with / and backward with ?:

/error          search forward for "error"
?warning        search backward for "warning"
n               next match
N               previous match

Searches support basic regular expressions:

/^ERROR         lines starting with ERROR
/failed.*disk   lines with "failed" followed by "disk"

Follow a file in real time

The -F flag makes less behave like tail -f — it keeps reading the file as new lines are added:

less +F /var/log/syslog

Press Ctrl+C to stop following and return to normal navigation mode.

Open at a specific line or pattern

less +100 file.txt          open at line 100
less +/pattern file.txt     open at first match of pattern

Useful options

less -N file.txt        show line numbers
less -S file.txt        chop long lines instead of wrapping
less -i file.txt        case-insensitive search
less -X file.txt        keep content on screen after quitting

Practical examples

View a compressed log without decompressing it first:

zless /var/log/syslog.gz

Read the output of a long command:

grep -r "error" /var/log/ | less
dmesg | less
journalctl | less

Search for errors in a log and read context around them:

less /var/log/nginx/error.log

Then type /404 to jump to the first 404 error.

less — Linux command line pager