possible with grep? find string and then output that and the rest of the file

captain_cthulhu · 05-18-2009, 10:33 AM

just wondering if this is possible using grep in conjunction with other commands - I am not really new to using Linux or the grep command but I am pretty new to many commands like sed and awk, so yeah, I am new to linux

I have a log file (text format) that puts date stamps on the first line of an error. the full error output however, could be made up of many lines (variable) that do not contain the date stamp. when I do a straight grep command, I only get the line containing the date I am searching for but I lose the error data contained on the lines below that.

I know that gnu grep can output a set number of lines after the found string but I don't have that installed and I am not able to add it to these machines (I can't add non-essential stuff to these production boxes). besides, since the error can be a variable number of lines, I can't use a set number to catch everything.

since these log files are very large, I'm just trying to cut my losses by finding my matching string with grep and then just output the whole rest of the file - this will at least cut down on the size of the output and can allow for manual perusing from the top of the output.

I'm new to these forums (just singed up a few mins ago! w00t!) and I thought this was the best place for me to ask this, sorry if it's not. any help is appreciated. thx!

captain_cthulhu · 05-18-2009, 10:37 AM

sorry, I found this after I posted:
http://www.linuxquestions.org/questi...a-file-450825/

I'm going to play around with this but if anyone has any suggestions, they are welcome.

one small difference is that I'm looking for string date like 'May 14' rather than a formal date format.

colucix · 05-18-2009, 10:46 AM

Using awk you can do something like

Code:

awk '/^May 14/{out="yes"}{if ( out ) print}' /path/to/log/file

Take in mind that in awk a condition is considered false if its value is zero or the null string; otherwise, the condition is true. In this case the variable out is a null string until "May 14" is encountered at the beginning of a line.

captain_cthulhu · 05-18-2009, 11:28 AM

perfect! thanks a ton and this will help me learn a bit more about awk

Tinkster · 05-18-2009, 12:09 PM

Or, slightly more lazy, use a range - with an end pattern
that doesn't exist.

Code:

awk '/^May 18/,/^@@@/' messages

Cheers,
Tink