UNIX for Dummies Questions & Answers

i had a server a while back that got bogged down every night because a job catted a large log file (>2gb) and piped that output to grep ... it was only when i stayed up overnight to trace this job when we found out what the issue was ... removing the cat pipe fixed the job ...

In the unix world I would not expect "grep filename" to outperform "cat filename| grep" on large files unless there was some bottleneck in the system.
The relevant unix commands are optimised for processing from a pipeline, with processing from a file as an exception. However I have noticed that "grep" and "sed" have much improved file handling in newer versions.

Just remembered a unix SVR3 system where "cat | grep" was chronically slow when straight "grep" was not. Had to increase disc buffer space in the kernel because default disc buffer settings were absurdly low to allow for the manufacturers "minimum system".

@kristinu O/P
Is this similar to one of your other threads?
https://www.unix.com/unix-dummies-que...sing-sort.html

One I only wanted a sort in order, the other is to remove part of an entry from all entries in a list and ensuring the remaining fields are identical.

Thanks for the explanation.