[Gllug] Off Topic: C File Descriptors

[John Edwards]

On Tue, Mar 04, 2008 at 12:10:02PM +0000, Mick Farmer wrote:
> Dear GLLUGers,
> 
> Is there a way of determining whether standard output and
> standard error are going to the same file/device?

Hi
Bash uses /dev/stdout and /dev/stderr, which on Linux are symlinks
to /proc/self/fd/1 and /proc/self/fd/2, which in turn point to the
device or file. Eg:

$ ls -al /proc/self/fd/[0-2]
lrwx------ 1 john john 64 2008-03-06 22:38 /proc/self/fd/0 -> /dev/pts/12
lrwx------ 1 john john 64 2008-03-06 22:38 /proc/self/fd/1 -> /dev/pts/12
lrwx------ 1 john john 64 2008-03-06 22:38 /proc/self/fd/2 -> /dev/pts/12

$ ls -al /proc/self/fd/[0-2] > /tmp/1 ; more /tmp/1
lrwx------ 1 john john 64 2008-03-06 22:38 /proc/self/fd/0 -> /dev/pts/12
l-wx------ 1 john john 64 2008-03-06 22:38 /proc/self/fd/1 -> /tmp/1
lrwx------ 1 john john 64 2008-03-06 22:38 /proc/self/fd/2 -> /dev/pts/12

$ ls -al /proc/self/fd/[0-2] > /tmp/1 2>&1 ; more /tmp/1
lrwx------ 1 john john 64 2008-03-06 22:39 /proc/self/fd/0 -> /dev/pts/12
l-wx------ 1 john john 64 2008-03-06 22:39 /proc/self/fd/1 -> /tmp/1
l-wx------ 1 john john 64 2008-03-06 22:39 /proc/self/fd/2 -> /tmp/1

HTH.

-- 
#---------------------------------------------------------#
|    John Edwards   Email: john at cornerstonelinux.co.uk    |
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