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Old 02-12-2003, 06:45 PM   #1
ferreter
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File descriptors odd question


Hello all,

I'm reading a book on some interesting linux hacks and came across one that I'm slightly stumped on. I know about file descriptors 0, 1, and 2 (input, output, error) and how you can direct them to go down the same stream like so: command 2>&1 | ..... or var=`command 2>$1` but where I'm getting a bit confused is when they swap the descriptors using the mostly unused 3-9 FDs like so:

command 3>&2 2>&1 1>&3 | ....

Why would I want to swap file descriptors in the first place? Any practical examples? Also it mentions closing the extraneous FDs like so: 3>&~ , is this the correct format? doesn't ~ stand for the home directory? If anyone can shed some light on this I'd appreciate it.

Thanks!
 
Old 02-13-2003, 05:13 AM   #2
Mik
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Chapter 16 of the Advanced bash scripting guide explains it pretty well I think.

And the syntax for closing a file descriptor is 3>&-
 
Old 02-13-2003, 10:21 AM   #3
ferreter
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Well that would make a bit more sense to me
 
  


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