Quoting Michael Sims <[EMAIL PROTECTED]>:
> [EMAIL PROTECTED] wrote:
> >>> ps aux | grep [l]pr
> >>>
> >>> This still lists all the processes that contain the string "lpr",
> >>> but it will not match the grep process itself anymore.
> >>
> >> Why is that? Isn't a bracket expression containing only one
> >> character exactly the same as the character by itself? Am I missing
> >> something blindingly obvious? :)
> >
> > As you point out, the brackets with one character amount to a range
> > of one character. The "[l]pr" regexp is intrepreted as "lpr", but
> > the grep command show up in ps as "grep [l]pr". This prevents grep
> > from matching its own process as it is output by ps.
>
> </me slaps forehead>
>
> Thanks, guess I didn't think hard enough. :) Nice trick, BTW...
>
>From the grep info manual:
7. Why do people use strange regular expressions on `ps' output?
ps -ef | grep '[c]ron'
If the pattern had been written without the square brackets, it
would have matched not only the `ps' output line for `cron', but
also the `ps' output line for `grep'. Note that some platforms
`ps' limit the ouput to the width of the screen, grep does not
have any limit on the length of a line except the available memory.
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