CODEWITHSUNDEEP
perlfilecharacter
Bob Sanders
Bob Sanders

Reputation: 4367

Detecting if a non-printable character has been found - Perl

My program is reading in a file, line by line. But if a non printable character is found (ex. characters with decimal value less than 32), then I just want to output an error message to the console.

Here is what I have

while($line=<FILE>){
print $line;
$line =~ s/^\s+//; #remove leading spaces
$line =~ s/\s+$//; #remove trailing spaces
if(/[\x00-\x1F]/){
    print "Found a non printable!";
}

I'm not sure if it is working, because I guess I'm not sure what the non printable would be in my file?

This is my current input file:

Pa$$word412
999

Wouldn't a carriage return be non-printable? Then shouldn't my warning message be printed?

Thanks!

Upvotes: 0

Views: 3351

Answers (2)

zgpmax
zgpmax

Reputation: 2847

You are reading the line into $line but not referencing this on your match. You would need to match $line explicitly like this:

if ($line =~ /[\x00-\x1F]/) {

Or, better yet, just put your line into $_:

while (<FILE>) {
    print;

    s/^\s+//; # remove leading spaces
    s/\s+$//; # remove trailing spaces

    if (/[\x00-\x1F]/) {
        print "WARNING -- Non-printables were found; they have been detected.";
    }
}

Trailing newlines will not trigger your warning because they match \s and are stripped by your trailing space removal. If you want a test case, put a tab character in your file; this should then match [\x00-\x1F].

Upvotes: 2

mob
mob

Reputation: 118605

A carriage return is non-printable, by your definition; but you are removing the carriage return from your input when you say

$line =~ s/\s+$//; #remove trailing spaces

Upvotes: 1

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