cat, less, more

Three ways to read a file

cat dumps the file straight to stdout. less is a pager — interactive, scrollable, searchable. more is the older simpler pager that less replaced (yes, the joke less is more is real).

cat — concatenate

• cat file — print contents.
• cat a b c — concatenate three files in order.
• cat -n file — number every line.
• cat -A file — show non-printing characters (tabs as ^I, line endings as $). Useful when a file looks fine but a tool says "unexpected token."

Don't pipe cat when you don't have to — grep foo file is cleaner than cat file | grep foo. The famous useless use of cat award.

less — the right pager

Inside less you can navigate without loading the whole file:

• Space / b — page down / up
• j / k — line down / up (vim-style)
• g / G — top / bottom
• /pattern — search forward, ?pattern backward
• n / N — next / previous match
• q — quit
• F — follow mode (like tail -f)

Less is the default pager

When man, git log, or git diff open, they're piping into less. Set $PAGER to less -R (raw colors) so colored output stays colored. $LESS="-RFX" is a common dotfile setting.