使用perl如何弄清楚如何关闭特定警告

Question

我有一些我正在处理的遗留代码.一次性清理太多了.它在s运算符内部使用\ 1.我查看了perllexwarn,发现我可以用'没有警告qw(语法)'来关闭它,但我通过反复试验做到了这一点.是否有更简单的方法从警告到关闭它的方式？

它正在做这样的事情:

use strict;
$_ = "abc";
s/abc/\1/;
no warnings qw(syntax);
s/abc/\1/;

它生成的消息是:

\1 better written as $1

Answer 1

我会创建一个全局信号处理程序,将其设置为一个BEGIN块,以便在早期编译,并且只跳过你不想要的警告,这样你仍然会得到任何潜在的意外和不相关的警告(即使在同一类别中,由于不必禁用整个事情):

use warnings;
use strict;

BEGIN {
    $SIG{__WARN__} = sub {
        my $warn = shift;
        return if $warn =~ /\\\d better written as/;
        warn $warn;
    };
}

my $x = 'abc';
$x =~ s/(abc)/\1/;

warn "a different warning\n";

输出:

a different warning

Answer 2

执行你的脚本

perl -Mdiagnostics ./a.pl

或暂时添加use diagnostics;到您的脚本.这将产生类似的东西

\1 better written as $1 at ./a.pl line 4 (#1)
    (W syntax) Outside of patterns, backreferences live on as variables.
    The use of backslashes is grandfathered on the right-hand side of a
    substitution, but stylistically it's better to use the variable form
    because other Perl programmers will expect it, and it works better if
    there are more than 9 backreferences.

请注意(W syntax)？这封信是以下之一,这个词就是您正在寻找的警告类.

• (W)警告(可选).
• (D)弃用(默认情况下启用).
• (S)严重警告(默认启用).
• (F)致命错误(可陷阱).
• (P)你永远不应该看到的内部错误(可陷阱).
• (X)一个非常致命的错误(不可用).
• (A)外来错误消息(不是由Perl生成的).

诊断从perldiag获取其信息,您可以手动搜索而不是使用use diagnostics;.

其他例子:

$ perl -Mdiagnostics -we'print undef'
Use of uninitialized value in print at -e line 1 (#1)
    (W uninitialized) An undefined value was used as if it were already
    [...]

$ perl -Mdiagnostics -we'no warnings qw( uninitialized ); print undef'

$ perl -Mdiagnostics -we'sub foo { } sub foo { }'
Subroutine foo redefined at -e line 1 (#1)
    (W redefine) You redefined a subroutine.  To suppress this warning, say
    [...]

$ perl -Mdiagnostics -we'no warnings qw( redefine ); sub foo { } sub foo { }'

$