Shell Programming and Scripting

Hi Everyone,

#!/usr/bin/perl
$a = ".a!";
if ($a =~ s/[A-Za-z0-9_-.]//g) {
print "invalid file name\n";
} else {
print "valid file name\n";
}

but the output is:
Invalid [] range "_-." in regex; marked by <-- HERE in m/[A-Za-z0-9_-. <-- HERE ]/ at ./a.pl line 5.

the linux file name should be A-Z, a-z, underscore, dash, dot.

Please advice where i made the mistake. Thanks

just escape the dash:

Code:

if ($a =~ s/[A-Za-z0-9_\-.]//g) {

you could write it like this too:

Code:

if ($a =~ s/[\w.-]//g) {

in which case the dash does not need to be escaped because its on the end and \w is the same as a-zA-Z0-9_

The dot never needs to be escaped in a character class no matter where it is positioned but a few characters do, like a dash.

Thanks Kevin,

But when i use:
#!/usr/bin/perl
$a = "a";
#if ($a =~ s/[A-Za-z0-9_-.]//g) {
if ($a =~ s/[A-Za-z0-9_\-.]//g) {
print "invalid file name\n";
} else {
print "valid file name\n";
}

i got
invalid file name

First, please use [code][/code] tags for sources, code/output listings, ...
Second, [A-Za-z0-9_] has it's own character class in Perl, \w
Third, if you want to match a literal dot, escape it, otherwise it'll match any character
Fourth, if you want to match something, don't run substitution on it.
Fifth, use appropriate logic. In your example the regex matches, but your logic says it's invalid.

This will work:

Code:

#!/usr/bin/perl
$a = "a";
if ( $a =~ /[-\w\.]/g ) {
    print "valid file name\n";
}
else {
    print "invalid file name\n";
}

Hi pludi, i tried if my filename $a = "a>";it says valid file name also, but this should be invalid.

Whoops, my bad. Change

Code:

/[-\w\.]/g

to

Code:

/^[-\w\.]+$/

This will check that the whole string, and fail if there's a non-matching character.

Thanks works perfect!