Re: fgrep execution time

[Stepan Kasal]

Hello,
  thank you, David, for your bug report.

On Tue, Feb 22, 2005 at 03:54:32PM +0100, Andreas Schwab wrote:
> David Bailey <address@hidden> writes:
> > ==> Using GNU grep
> >
> > time yes "a very long file" | \
> >     head -10000 | /usr/local/bin/fgrep -f /dev/null
> > 0.00u 0.01s 0:07.95 0.1%
> >
> > time yes "a very long file" | \
> >     head -100000 | /usr/local/bin/fgrep -f /dev/null
> > 0.05u 0.03s 1:27.24 0.0%
> >
> > time yes "a very long file" | \
> >     head -1000000 | /usr/local/bin/fgrep -f /dev/null
> > 0.27u 0.14s 14:35.35 0.0%
> >
> > Over 14 minutes for a 17MB file.
> 
> Looks like you are timing something unrelated.  Note that the CPU time is
> 0.27+0.14 seconds, ie. neglectable, thus GNU grep is unlikely to blame for
> the big real time.

I'm not sure I understand what the various numbers in the output of "time"
mean, yet I'm afraid GNU grep can be the one to blame.

GNU grep 2.5.1 is awfully inefficient with non-C locales.

How would the times look like if you tried the following?

time yes "a very long file" | \
    head -10000 | LC_ALL=C /usr/local/bin/fgrep -f /dev/null

Have a nice day,
        Stepan Kasal