Shell Programming and Scripting

First or last in a reversed file - my head starts spinning. How about posting in- and output samples, connecting them with some logic description and pointing to the one "Feb 2" that you want?

This is ridiculous.

In addition to what RudiC has already said...

What do you mean by abort? (You do understand that the entire input file has to be read, don't you?) Are you saying you want to process to terminate as the result of a SIGABRT signal instead of terminating with an exit 0?

Explain what should happen in the corner cases. (Such as if the target string is not found.)

i apologize if i wasn't clear.

when i said abort, i meant terminating with an exit code. my use of the word abort seems to have derailed this completely and that is my fault. again, my apologies.

say the content of the file is this:

Code:

Feb  1 a jakfif 
Feb  1 nahit 
Feb  2 a jakf
Feb  2 a bcaa
Feb  2 a bc
Feb  3 cna f
Feb  3 jaf af
Feb  4 uiaf aj
Feb  6 whatitoa

the code you supplied is doing this:

Code:

feb  6 whatitoa
Feb  4 uiaf aj
Feb  3 jaf af
Feb  3 cna f
Feb  2 a bc

notice how it stops at the first occurrence of the "Feb 2" string.

what i want it do is this:

Code:

Feb  6 whatitoa
Feb  4 uiaf aj
Feb  3 jaf af
Feb  3 cna f
Feb  2 a bc
Feb  2 a bcaa
Feb  2 a jakf

---------- Post updated at 09:39 PM ---------- Previous update was at 09:37 PM ----------


my apologies for the confusion.

So you wanted the last occurrence of you pattern in the REVERSED file; not the last occurrence in the file. Try:

Code:

awk '
{	a[NR] = $0
}
!last && /Feb  2/{
	last = NR
}
END {	while(NR >= last)
		print a[NR--]
}' mail.log

You still refuse to answer the question about what should happen if the pattern you're looking for doesn't appear at all, so if I guessed wrong again about what you want in that case, you're on your own to fix it.

And, I'll repeat the usual warning... If you want to try this on a Solaris/SunOS system, change awk to /usr/xpg4/bin/awk, /usr/xpg6/bin/awk, or nawk.

i will take heed of your warning.

if the pattern is not found, i'm totally ok with the code not showing anything at all.

btw, the log format is in the typical syslog format.

I'm glad that you're OK with the code not showing anything. Unfortunately, if your pattern is not found that code prints the entire file backwards and then prints an empty line.

So why is a file in the typical syslog format named mail.log?