如果我有一个函数可能会传递文件名或各种文件句柄或类型团,该函数如何区分这些参数——包括区分,例如,*DATA
之间的区别。和 *STDIN
?
根据目前收到的答案更新了代码 谢谢大家。
use strict;
use warnings;
use FileHandle;
sub file_thing_type {
my ($f) = shift;
my $type;
my $r = ref $f;
if ($r eq 'GLOB' or ref(\$f) eq 'GLOB'){
# Regular and built-in file handles.
my $fn = fileno $f;
if (defined $fn){
my %built_in = (
'STDIN' => fileno(*STDIN),
'STDOUT' => fileno(*STDOUT),
'STDERR' => fileno(*STDERR),
'DATA' => fileno(*DATA),
);
for my $k (keys %built_in){
if (defined $built_in{$k} and $built_in{$k} == $fn){
$type = $k;
last;
}
}
$type = 'regular file handle' unless defined $type;
}
else {
$type = 'non-IO glob';
}
}
elsif ($r){
# A reference of some kind.
$type = $r;
# Might be an IO object. Has it been opened?
{
no warnings 'unopened';
$type .= ' opened' if -f $f;
}
}
else {
# File name or just some other value?
$type = -f $f ? 'file name' : 'other';
}
return $type;
}
open(my $h, '<', $0) or die $!;
printf "%12s => %s\n",
$_->[0],
file_thing_type($_->[1])
for (
[ 'handle', $h ], # regular file handle
[ 'DATA', *DATA ], # DATA if source has DATA section; else non-IO glob
[ 'STDIN', *STDIN ], # STDIN
[ 'STDOUT', *STDOUT ], # STDOUT
[ 'STDERR', *STDERR ], # STDERR
[ 'FOO', *FOO, *FOO ], # non-IO glob
[ 'FileHandle', FileHandle->new ], # FileHandle
[ 'FileHandle', FileHandle->new($0) ], # FileHandle opened
[ 'file name', $0 ], # file name
[ 'not file', '' ], # other
[ 'misc', {bar=>1} ], # HASH
);
__END__
最佳答案
更新:区分可能分配给 *DATA
的变量的问题或 *STDIN
globs 是 fileno
的工作:
sub data_or_stdin { my $x = shift; if (fileno($x) == fileno(DATA)) { return "DATA"; } elsif (fileno($x) == fileno(STDIN)) { return "STDIN"; } else { return "NEITHER"; } } print "DATA: ", data_or_stdin(*DATA), "\n"; print "STDIN: ", data_or_stdin(*STDIN), "\n"; open(ZZZ, ">>", "zzz"); close ZZZ; open(ZZZ, "<", "zzz"); print "ZZZ: ", data_or_stdin(*ZZZ), "\n"; close ZZZ; open($fh, "<", "zzz"); print "\$fh=ZZZ: ", data_or_stdin($fh), "\n"; close $fh; $fh = *DATA; print "\$fh=DATA: ", data_or_stdin($fh), "\n"; $fh = *STDIN; print "\$fh=STDIN: ", data_or_stdin($fh), "\n"; __END__ stuff;
$ perl data_or_stdin.pl DATA: DATA STDIN: DATA ZZZ: NEITHER $fh=ZZZ: NEITHER $fh=DATA: DATA $fh=STDIN: DATA
If $f
is a filehandle, then either ref $f
or ref \$f
will be "GLOB"
If $f
is a scalar, then ref \$f
will be "SCALAR"
.
sub filehandle_or_scalar {
my $x = shift;
if (ref $x eq "GLOB" || ref \$x eq "GLOB") {
return "filehandle";
} elsif (ref \$x eq "SCALAR") {
return "scalar";
} else {
return "not filehandle or scalar";
}
}
print "STDIN: ", filehandle_or_scalar(*STDIN), "\n";
print "\$_: ", filehandle_or_scalar($_), "\n";
open($fh, ">", "zzz");
print "\$fh: ", filehandle_or_scalar($fh), "\n";
print "string: ", filehandle_or_scalar('file.txt'), "\n";
print "ref: ", filehandle_or_scalar(\$x), "\n"
###########################################
$ perl filehandle_or_scalar.pl
STDIN: filehandle
$_: scalar
$fh: filehandle
string: scalar
ref: not filehandle or scalar
关于perl - Perl 子例程如何区分文件名、文件句柄、*DATA 和 *STDIN?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/2308597/