問題描述
Perl 隱式關閉重置 $. 多變的 (Perl implicit close resets the $. variable)
The documentation for Perl's close states that $. isn't reset if you use the implicit close done by open. I was trying to see exactly what this meant, but couldn't get it to happen. Here's my script:
use strict;
use warnings;
use autodie;
my @files = qw(test1.txt test2.txt test3.txt);
#try with implicit close
for my $file (@files){
open my $fh, '<', $file;
while(<$fh>){
chomp;
print "line $. is $_\n";
}
#implicit close here
}
And here are the contents of all three of the files that are read in:
line 1
line 2
line 3
line 4
line 5
line 6
line 7
line 8
line 9
line 10
Since I don't explicitly call close, the implicit close should be used (I think) and $. shouldn't be reset. However, when I run the script, I get this output, showing that $. is reset:
line 1 is line 1
line 2 is line 2
line 3 is line 3
line 4 is line 4
line 5 is line 5
line 6 is line 6
line 7 is line 7
line 8 is line 8
line 9 is line 9
line 10 is line 10
line 1 is line 1
line 2 is line 2
line 3 is line 3
line 4 is line 4
line 5 is line 5
line 6 is line 6
line 7 is line 7
line 8 is line 8
line 9 is line 9
line 10 is line 10
line 1 is line 1
line 2 is line 2
line 3 is line 3
line 4 is line 4
line 5 is line 5
line 6 is line 6
line 7 is line 7
line 8 is line 8
line 9 is line 9
line 10 is line 10
It sure looks like it's being reset to me. Is my understanding of the documentation wrong? Can someone show me under what circumstance the implicit close will not reset $.?
By the way, I'm using Strawberry 5.16.1.
‑‑‑‑‑
參考解法
方法 1:
$. is not actually a global variable, it is an attribute of the most recently read filehandle. And you are using a new filehandle in each iteration through the loop.
Modifying your code like so "fixes" it:
my $fh;
for my $file (@files){
open $fh, '<', $file;
(by Nate Glenn、ysth)