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When using echo "foo">> bar.txt more than once it appends to the end of a file. How to overwrite bar.txt each time?

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Dennis' answer is correct. See man bash and search (using /) for the section on "REDIRECTION". Specifically subsections "Redirecting Output" and "Appending Redirected Output". – RedGrittyBrick Apr 19 '12 at 18:57
up vote 16 down vote accepted

> is for redirecting to a file (overwriting it), while >> is for appending.

To overwrite bar.txt, use this:

echo "foo" > bar.txt
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More commonly, > is referred to as redirecting (standard output to a file) whilst the pipe symbol | is referred to as piping (standard output to another process). You run the risk of confusing people like me when you refer to > as 'piping' – RedGrittyBrick Apr 19 '12 at 18:52
    
@RedGrittyBrick: I've seen piping in a few books (and I've been saying it for years), but redirecting seems to be far more common. Thanks. – Dennis Apr 19 '12 at 18:56
    
@Dennis Piping is using the pipe | for connecting the output of one program/command to the input of another. Related. – Daniel Beck Apr 19 '12 at 18:58
    
@DanielBeck: I meant I saw piping to a file. Example: Learn Windows PowerShell in a Month of Lunches - Piping to a file or printer – Dennis Apr 19 '12 at 19:01
    
Note that according to page 43, in PowerShell > foo is just syntactic sugar for | Out-File foo, and therefore is a form of piping ;-) – Daniel Beck Apr 19 '12 at 19:06

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