[PATCH perlfaq5] "How can I manipulate fixed-record-length files?"
[email protected] (Iain Truskett)
| Newsgroups | perl.perlfaq.workers |
|---|---|
| Message-ID | <[email protected]> |
Heyo, The attached patch stops the answer in question from using symbolic references and instead gets to illustrate a nice use of hash slices. I think it makes the code easier to read. I may be wrong =) cheers, -- Iain.
fixed.patch
(text/plain, 1.7 KB)
Index: perlfaq5.pod
===================================================================
RCS file: /cvs/public/perlfaq/perlfaq5.pod,v
retrieving revision 1.29
diff -u -r1.29 perlfaq5.pod
--- perlfaq5.pod 12 Aug 2003 02:44:46 -0000 1.29
+++ perlfaq5.pod 22 Nov 2003 14:21:05 -0000
@@ -162,22 +162,23 @@
# 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: <$$var>\n";
+ my $PS_T = 'A6 A4 A7 A5 A*';
+ open my $ps, '-|', 'ps';
+ print scalar <$ps>;
+ my @fields = qw( pid tt stat time command );
+ while (<$ps>) {
+ my %process;
+ @process{@fields} = unpack($PS_T, $_);
+ for my $field ( @fields ) {
+ print "$field: <$process{$field}>\n";
}
- print 'line=', pack($PS_T, $pid, $tt, $stat, $time, $command),
- "\n";
+ print 'line=', pack($PS_T, @process{@fields} ), "\n";
}
-We've used C<$$var> in a way that forbidden by C<use strict 'refs'>.
-That is, we've promoted a string to a scalar variable reference using
-symbolic references. This is okay in small programs, but doesn't scale
-well. It also only works on global variables, not lexicals.
+We've used a hash slice in order to easily handle the fields of each row.
+Storing the keys in an array means it's easy to operate on them as a
+group or loop over them with for. It also avoids polluting the program
+with global variables and using symbolic references.
=head2 How can I make a filehandle local to a subroutine? How do I pass filehandles between subroutines? How do I make an array of filehandles?