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Re^3: Regular Expressions question

by Lotus1 (Curate)
on Oct 30, 2012 at 03:24 UTC ( #1001449=note: print w/replies, xml ) Need Help??


in reply to Re^2: Regular Expressions question
in thread Regular Expressions question

my @check = grep { chomp $_; $_ } <DATA>;

Map should be used for this not grep. Consider the following.

use warnings; use strict; my @check = grep { chomp $_; $_ } <DATA>; print ">>@check<<" __DATA__ line1 0 line3

The output is:

>>line1 line3<<

Grep looks at the value the block returns and if true it returns $_. Map is used to do something to each element and pass along the result from each.

To me it is clearer and simpler to do this:

my @check = <DATA>; chomp @check;

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[Corion]: Maybe doing a double-fork (daemonizing) can make go that information away, but maybe not
[Corion]: But I think my knowledge of unix/Linux datastructures is several decades out of date, so I don't really know what information it keeps on processes
[oiskuu]: The useful bits that relate to your process can be found under /proc/self. What information are you thinking of? Tty name?
[tye]: I just daemonized and getlogin() still knew who I had been.
[tye]: perhaps loginuid ? Not that I concede that something not being in /proc means it is not useful.
[Corion]: tye: That's really interesting, but maybe it is because getlogin() returns the name, or the uid, so if that user has been replaced by another user with the same uid in the meantime, that's no problem to the system...
[davido]: or on ubuntu /var/run/utmp
[Corion]: Otherwise, I would imagine that a user with a process still alive would lock that information in memory.
[davido]: so last -f /var/run/utmp on ubuntu provides similar (though more verbose) info

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