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2月1日 Little annoying things with AIX, ps and grepWarning: if shell scripting and regex aren't your bag, stop reading ;)
Silly little bug I had to hunt down today while looking at an Oracle monitoring script someone wrote to use with Nagios..
Consider this output:
root@test(/tmp) # ps -ef | grep ora_pmon
ora102 659494 1 0 Jan 26 - 1:32 ora_pmon_dev oracle 1011724 1 0 Oct 31 - 14:13 ora_pmon_deva If you want to see if the db process is running, you just need to check for ora_pmon_<DBNAME>. Easy. But in this output, if I grep for 'ora_pmon_dev", I could get a hit even if only 'deva' is up and not 'dev'.. So you need to specify in the grep that you want the string to be at the END of the line, with no extras. So using a regular expression you'd use "ora_pmon_dev$".
Thing is, it didn't work!?
After half an hour of testing this, I discovered that 'ps' under AIX adds a trailing space to each line of output.
Easy - just adjust the regex to include the extra junk.. Again, it didn't work.. I discovered two things..
They're linked.. I tried to use "ora_pmon_dev\s*$" as a pattern. \s* to allow (optional) whitespace. It still didn't work.. Some more detective work and I found out that AIX's grep didn't understand \s at all. I guess I'm just too used to it in perl..! I usually get into the habit of using \s* to cover all whitespace cases, but here I guess testing for spaces-or-tabs will have to do:
Where you type a space an a tab inside the brackets.. Makes it a lot harder to read and maintain afterwards, which I guess is exactly why \s exists in perl (and probably other regex engines). |
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