Current Perl documentation can be found at perldoc.perl.org.
Here is our local, out-dated (pre-5.6) version:
The most efficient way is using
pack()
and
unpack().
This is faster than using
substr()
when take many, many strings. It is slower for just a few.
Here is a sample chunk of code to break up and put back together again some fixed-format input lines, in this case from the output of a normal, Berkeley-style ps:
# sample input line: # 15158 p5 T 0:00 perl /home/tchrist/scripts/now-what $PS_T = 'A6 A4 A7 A5 A*'; open(PS, "ps|"); print scalar <PS>; while (<PS>) { ($pid, $tt, $stat, $time, $command) = unpack($PS_T, $_); for $var (qw!pid tt stat time command!) { print "$var: <$$var>\n"; } print 'line=', pack($PS_T, $pid, $tt, $stat, $time, $command), "\n"; }
We've used $$var
in a way that forbidden by use strict 'refs'
. That is, we've promoted a string to a scalar variable reference using
symbolic references. This is ok in small programs, but doesn't scale well.
It also only works on global variables, not lexicals.