[clug] Made to fix it :-)

[Paul Wayper]

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Hi all,

Just thought I'd share a little amusement from today: we had to search through
some logs for stuff.  There are quite a few log files per day and we had to
scan through a week or so.  It's an eight processor machine so I wanted to do
it in parallel and, in explaining the problem to a friend, I realised that I
had all the tools I needed: 'make'.  I wrote a Makefile similar to the following:

- -8<-------------

%.txt: %.gz
	zgrep -e 'email at address' %< > %@ || /bin/true

SOURCES := $(wildcard *.gz)

all: $(patsubst %.gz, %.txt, $(SOURCES))

- -8<-------------

The first two lines say: things with .gz can be transformed into .txt files by
zgrep taking the source (%<) and producing the target (%@).  We use '||
/bin/true' because grep has an annoying habit of returning false if the
pattern wasn't found, and make detects this and thinks this a failure to build
the source file; so we convince it that whatever it returns, it returns true.

Then we collect a list of the source files, and make the 'all' target depend
on a list of those files with the .gz extensions changed to .txt.  A 'make -j
8' and away it goes :-)  And the best part is that if we stop the process at
any point, make will remove the half-completed .txt files and the same command
restarts the whole thing.

I know Tridge said using parallel make is a bad thing, but in this case I
think I can probably get away with it... :-)

Anyone else have some neat tricks up their sleeve to make their sysadmin life
less painful?

Have fun,

Paul
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