Command Line usability basics: Redirection

Mar 29, 2007 - 4 Comments

Mac OS X is so user friendly that many Mac users probably don’t know they’re sitting on top of a powerful Unix base, accessible by the Terminal app. Our feeling is that since the command line is there, you should be able to use it to some extent. In our continued quest to propagate OS X command line knowledge, we bring you some information on the extremely useful redirect utilities. Redirects allow you to take the output of certain commands and create new files or add to existing ones with this data, very useful indeed.

Command Usage
command > newfile Redirects the output of the command to newfile
command >> existingfile Appends the output of the command to the end of existingfile

Examples of redirects in use:

If you wanted to create a text file with data from the ps command, but controlled only for Dashboard related processes running, this is what you would type at the command line:
ps -aux | grep Dashboard > dashboarddata.txt

If you wanted to add at the end of the file we just created, dashboarddata.txt a list of Widgets you have installed, you would type the following:
ls -l /Library/Widgets >> dashboarddata.txt

The uses for redirection are endless and you’ll find that the more time you spend in the command line, the more you’ll want to use redirect for aiding certain tasks.

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Posted by: OSXDaily in Command Line, How to, Mac OS X, Tips & Tricks

4 Comments

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  1. anon says:

    thanks, you’re slowly making me less of an idiot in the command line department, but I have to admit I don’t find any practical use for much of this knowledge…

    Why would you really use redirects like this in a real world setting?

  2. [...] [link][more] [via: reddit.com: newest submissions | article link] [...]

  3. Brian Burleigh says:

    @ anon

    g++ file1.cpp file2.cpp -o program.o >> compileinfo.txt

  4. [...] It’s a month old now, but I’ve been meaning to write on this post that, from its title, claimed to be a tutorial on Unix-based command line redirection. I use *nix systems on a regular basis, and I actually got suckered into clicking to this article. It was a waste of time. And then I got even annoyed by thinking about things on a deeper level. I hate thinking. [...]

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