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SubjectRe: sed not working on /proc files
On Mon, 26 Apr 1999, Stefan Monnier wrote:

> How do you explain the following problem (with 2.2.6):
>
> # (sed 's/a/a/') </proc/modules
> # (cat | sed 's/a/a/') </proc/modules
> nfsd 147288 1 (autoclean)
> nfs 27856 2 (autoclean)
> lockd 29000 1 (autoclean) [nfsd nfs]
> sunrpc 48492 1 (autoclean) [nfsd nfs lockd]
> autofs 8872 1 (autoclean)
> 3c59x 17456 1 (autoclean)
> opl3 10264 0
> cs4232 2264 0
> ad1848 15152 0 [cs4232]
> uart401 5628 0 [cs4232]
> sound 55080 0 [opl3 cs4232 ad1848 uart401]
> soundcore 2208 6 [sound]
> binfmt_misc 3108 0
> st 23352 0
> softdog 948 1
> unix 10056 72 (autoclean)
> #
>

-r--r--r-- 1 root root 0 Apr 26 17:28 /proc/meminfo
^_______ zero
It happens because files in /proc have zero length. These are not
real files. To use `sed` and utilities that do lseek you can `cat`
through a pipe as you have done. Sed's first 'lseek()' returns ESPIPE
which tells it to not do that again -- and everything is fine.


Cheers,
Dick Johnson
***** FILE SYSTEM WAS MODIFIED *****
Penguin : Linux version 2.2.6 on an i686 machine (400.59 BogoMips).
Warning : It's hard to remain at the trailing edge of technology.

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