find if a string is null 3

[kaancho12]

hi i am trying to go through a content of a file and check for null character...but its not working--

$htmlcontent = "";
if ($html eq "0"){
# to check for null char i use:
if ($char ne " "){
$htmlcontent = $htmlcontent . $char;
}
}
anybody have ideas as to what else will work???
ko12

 

[Rieekan]

Well, to check for a non-null string would be:

if (!$string)
{
    #process here
}

Not sure what you mean by a null character. Are you specifically looking for a space or tab or something as the null value?

- Rieekan

 

[1DMF]

If you want to check for empty then you musn't have a space between the quotes.

Perl has a built in function that when you ask

if($varname ne ""){
}

or

if($varname eq ""){
}

if $varname is NULL or has no value it is conveted to an empty string first and then evaluates against "".

"" is NOT NULL it is an EMPTY STRING.

hope that makes sense

 

[kaancho12]

hi,
thanks for replies.
by null --i meant empty spaces.
i tried both
if($varname ne ""){
}
and
if (!$string)
but they did not work---any ideas??
thanks

 

[dmazzini]

if ( $variable =~ /^$/ ) {
print "Variable is null\n";
}

if ( $variable !~ /^$/ ) {
print "Variable is not null\n";
}



dmazzini
GSM System and Telecomm Consultant

 

[Rieekan]

To look for a string that only has spaces, you can do the following, but it will check for any whitespace character (tab, carriage return, enter, space)

 if ( $variable =~ /^\s$/ ) {
      print "Variable is null\n";
  }

- Rieekan

 

[ishnid]

Just a slight alteration to Rieekan's code to allow for any number of spaces, rather than just one:

 if ( $variable =~ /^\s*$/ ) {
      print "Variable is null\n";
  }

 

[Rieekan]

Oops, good catch ishnid. It's just too early in the morning to be thinking.

- Rieekan