2008-05-30
The fun of awk
I like awk, I really do, but sometimes it really irritates me. Take, for
example, this fun little awk program:
awk 'BEGIN {print "5" == "05"}' /dev/null
You might rationally expect this to print '1' (awk's boolean truth
value). As I found out once, you would be sadly mistaken; this is
false, presumably because awk winds up doing a string comparison
instead of a numeric one. Too bad if you're reading one set of fields
that are zero-padded and one set that aren't.
(The workaround is add 0 to the "05" to force the numeric
interpretation; "5" == ("05"+0) comes out true.)
This shows two drawbacks of the sort of magical conversion between
numbers and strings that awk does. First, this sort of stuff involves
heuristics, and heuristics are inevitably wrong sooner or later. And
second, if you do not have the fine details carefully memorized you can
wind up surprised.
At the same time such magical conversions live on because they are oh so
very handy when you are banging things in a hurry. Considering the sorts
of things that awk was designed for, this is completely the right
decision for it; having to write explicit Python-style conversions all
the time would probably drive me up the wall, however much I like them
in Python.