Shell Programming and Scripting

I need to parse a large log say 300-400 mb
The commands like awk and cat etc are taking time.
Please help how to process.
I need to process the log for certain values of current date.
But I am unbale to do so.

What about good old grep?

It is also not working

I personally doubt that grep would be more efficient that awk for large files. Please post sample input and ouput files.

And show us the regex you are using. Simple greps would take a few seconds max unless your disks are very slow. It's reading the file linearly so you can't get much faster performance than that. If cat is too slow, there really isn't much hope in making it fast enough, other than replacing the disk, or managing the file in a different way (split into smaller chunks? Import into a DBMS?)

the log is of the form

05/29/08 01:56:53 nsrexecd: select() error: Invalid argument
05/29/08 01:56:53 nsrexecd: select() error: Invalid argument
05/29/08 01:56:53 nsrexecd: select() error: Invalid argument

i need to take the log for 13 pm of last day to 13 pm of cureent date.
Please help to get it using tail....a none of the grep , cat , awk etc are working....

Code:

egrep '^05/(29/08 (1[3-9]|2[0-3])|30/08 (0|1[0-2]))' logfile

For automation, the regular expression can be generated by date or a simple Perl script. It would be much easier if you could simply do it by date, though.