Useful Utility: less

Less is more.

That’s the common joke about less- It provides the same functionality as the older utility, more; but oh, how much more than more!

Less allows you to easily scan backwards as well as forwards- something more is not too good at (though it is possible). Less also allows you to navigate with arrow keys, page up and page down, home and end.

Less provides a quick way to view files as well- Many editors (like vim) need to read an entire file first, and often create a temporary copy (for editing) of the file. This isn’t a problem until you try to browse a 56 gig log file of a rabid JBoss instance- if your root directory isn’t large enough, chaos ensues. Less circumvents this by only loading a page at a time. Yes- searches do take longer, but it beats crashing a system.

Useful Commands:

• R: Repaints the screen, rereading the file from the disk. useful if the file is constantly changing (like a logfile)
• / and ?: Just like in vim, used for searching forwards and backwards
• g and G: Jumps to the top or bottom of the file, just like vim
• :n and :p: Jump to the next/previous file (if you pass less more than one file)
• q: quits. slightly important
• ! [cmd]: runs a given command outside of less- useful if you can’t remember the output of another command and need a quick reminder (ifconfig, tail, route, ls, etc)

Useful Flags:

• -N: Shows line numbers
• -s: squeeze adjacent blank lines into one
• -R: shows raw control characters, a.k.a. “turns color on!”

As usual, there are dozens of more options, flags, variables and behavior- you’d be surprised what less can do for you.