[cupidvogel]

Hi, suppose I have a file named first.txt from which I want to read. Suppose the text file looks like this:

Quote

I like you.
I feel your soul.

Now if I use this:

open cool, "< first.txt";
print <cool>;

the entire file content is printed, but if I use this:

open cool, "< first.txt";
print length(<cool>);

only 12 is printed (the length of the first line only, including newline), whereas it should be 27 (the length of the entire file content), because <cool> contains the entire file content, right, otherwise how could it have printed the entire content? So why is this happening?

[dsherohman]

cupidvogel, on 20 January 2012 - 07:41 AM, said:

it should be 27 (the length of the entire file content), because <cool> contains the entire file content, right, otherwise how could it have printed the entire content?

Many functions and operators in Perl are sensitive to context. When you use them in a different context, they produce different results.

cupidvogel, on 20 January 2012 - 07:41 AM, said:

print <cool>;

The 'print' function can take a list of arguments (e.g., 'print $foo, $bar, $baz;'), so this places <cool> into list context. In list context, the <> operator returns the entire contents of the file, allowing you do do things like

my @entire_file_content = <cool>;

cupidvogel, on 20 January 2012 - 07:41 AM, said:

print length(<cool>);

The 'length' function only takes a single argument, so this evaluates <cool> in scalar context. In scalar context, the <> operator returns one line at a time, allowing you to do things like

while (my $line = <cool>) {
  process_one_line($line);
}

Most people seem to find context one of the trickier concepts in Perl to grasp, but it's a very powerful tool once you get comfortable with it.

[cupidvogel]

Wow. That was cool. I was well-versed in Python, and I never imagined that any language will impress me after Python, given it's so succinct and comes with tons of features. But Perl did just that, it is awesome!