10 bad UNIX or Linux command line usage patterns to avoid

by on December 13, 2006 · 9 comments· LAST UPDATED December 13, 2006

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Michael Stutz is author of The Linux Cookbook, has published excellent set of 10 bad UNIX usage patterns. These are applies to Linux, OS X shell as well :)

You can adopt 10 good habits that improve your UNIX / Linux command line efficiency -- and break away from bad usage patterns in the process. This article takes you step-by-step through several good, but too often neglected, techniques for command-line operations. Learn about common errors and how to overcome them, so you can learn exactly why these UNIX habits are worth picking up.

Adopt 10 good habits

Ten good habits to adopt are:

1. Make directory trees in a single swipe.
2. Change the path; do not move the archive.
3. Combine your commands with control operators.
4. Quote variables with caution.
5. Use escape sequences to manage long input.
6. Group your commands together in a list.
7. Use xargs outside of find.
8. Know when grep should do the counting -- and when it should step aside.
9. Match certain fields in output, not just lines.
10. Stop piping cats.

Learn 10 good UNIX usage habits

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{ 9 comments… read them below or add one }

1 Doug Keester December 13, 2006 at 6:01 pm

Overall a decent article.

However, there is no need to use ‘xargs’ with ‘find’ since ‘find’ has the -exec flag which does the same thing and doesn’t require a pipe.

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2 nixCraft December 13, 2006 at 6:46 pm

Doug,

I must agree with. It always good idea to use KISS philosophy.

Appreciate your post.

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3 Jonathan December 14, 2006 at 3:21 am

Yeah, but it will be a cold day in hell before I remember the bizarre -exec syntax without trying it a dozen times or more! “Now where does {} go? And what about that semi-colon? Or is it a colon?” :-)

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4 Paul McNamara December 18, 2006 at 6:23 pm

Not being fluent in UNIX myself (not speaking a word, actually), I had a little fun with Stutz’s list, in particular, No. 10: “stop piping cats.”
http://www.networkworld.com/community/?q=node/9764

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5 nixCraft December 18, 2006 at 11:10 pm

LOL @ Paul

Thanks for sharing with us.

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6 pip February 12, 2007 at 4:19 pm

Hey why stop piping cat’s? What’s bad in doing so? redirect the stdinput?

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7 pip February 12, 2007 at 4:21 pm

sorry forgot to tick the notify box… this should solve it… cheers

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8 Christopher Cashell May 11, 2008 at 6:22 am

I know this was posted a long time ago, but in case someone else comes across it, a note in response to:

However, there is no need to use ‘xargs’ with ‘find’ since ‘find’ has the -exec flag which does the same thing and doesn’t require a pipe.

That’s not actually true. In many simple cases, you can use -exec. However, depending on the number of items returned by find, and the action you’re taking, it can be a *lot* less efficient using -exec in comparison to xargs.

For example, say you are building a list of files to delete with find, and it is going to return 100k files. If you use find fpo/ -exec rm -rf '{}' \;, then you will be exec()’ing rm 100k times. If you use find foo/ -print | xargs rm -rf, then xargs will build the command argument list for rm to an appropriate length. For the sake of argument, say it runs rm with 1000 entries each time. That means you’re now only exec()’ing rm 100 times, instead of 100k times. When you’re dealing with large numbers like this, the time and CPU cycles to exec() your command that many times can have a very real performance impact.

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9 Kevin June 6, 2008 at 12:04 am

-exec starts a separate shell for each command.
xargs does it in one process.

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