UNIX for Advanced & Expert Users

Hi,

I've got a query regarding which of the following is more efficient & why -

Code:

cat <filename>|cut -d'*' -f2- > <newfilename>
or 
cut -d'*' -f2- <filename> > <newfilename>

Thanks.

Spawning two processes can never be better than one...so based on this you can figure out which is more efficient.

Spawning two processes can be better if the single process does something stupid, but cat isn't even doing anything useful here. See useless use of cat.

That would be the exception and assumes the scripter doesnt know what to do with that one spawned process.

For trivial file size the main overhead is loading programs and opening the file. Reading the file directly with "cut" makes sense.
For large files the argument is less clear unless the command is better than "cat" at reading data from disc.

For example with a 600 Mb text file:

Code:

timex cat bigfile|cut -f2 -d- >/dev/null

real       17.60
user        0.17
sys         2.62

timex cut -f2 -d- bigfile >/dev/null

real       17.45
user       16.10
sys         1.32

Here reading the file direcly in "cut" is fractionally quicker but has a greater impact on the system overall.

Does this system have multiple cores? That'd be the only way I could explain that -- one core runs 'cat' and reads the file while the other runs 'cut' to process it. This may mean using twice as much CPU power for a nearly unmeasurable CPU gain.

Experts,

This is slightly beyond my comprehension but let me try to put it in my words to verify.

. combining cat & Cut will cause spawning and will utilize more CPU threads which is fine for smaller files.
. In case of bigger files as in my case, it is better to directly operate the Cut command on the file. This will result in optimum CPU utilization.

Please correct me.

This turned out be little more complex than I though. Thanks.