perlist语法错误，位于wordlist.pl第11行，靠近“）$ fh”

Question

my $fn= "words.txt";
open ($fn), $file;
if (! -e "$fh") $fh="STDIN";
while (<$fn>){;
    my $total_words = @words; #All word count
    my %count;
    $count{$_}++ for @words; # Here are the counts
    my $uniq_words  = scalar keys %count; # Number of uniq words
}
# Print sorted by frequency

print "$_\t$count{$_}" for (sort { $count{$b} <=> $count{$a} } keys %count);

close FILE;
exit 0

I'm getting this error:

Scalar found where operator expected at wordlist.pl line 8, near ") $fh"
        (Missing operator before $fh?)
syntax error at wordlist.pl line 8, near ") $fh"
Execution of wordlist.pl aborted due to compilation errors.

please help

Answer 1

Perl always requires braces around the code after a conditional:

You wrote:

if (! -e "$fh") $fh="STDIN";

You should write either:

if (! -e "$fh") { $fh="STDIN"; }

Or:

$fh = "STDIN" if ! -e "$fh";

Those are syntactically correct. The code is semantically shot to pieces, though. To open a file, use:

open my $fh, '<', $fn or die "Failed to open $fn";

And always use use strict; and use warnings; . Perl experts use them to ensure they've not made silly mistakes. Novices should do the same.

Answer 2

open ($fn), $file;

Remove the parentheses here.

The first argument is the filehandle, and the second is the filename. You're using $fn as both the filename and filehandle, whereas $file is never defined.

if (! -e "$fh") $fh="STDIN";

You can't leave off the braces around a block like this. I'm also not sure what $fh is supposed to be since you never use it again.

You seem confused about Perl's syntax. How are you learning Perl?

Answer 3

Probably you got confused between file name $file and file handle $fh

Try changing your first three lines to

my $file= "words.txt";
if (! -e $file) {
  my $fh = *STDIN;
} else {
  open my $fh, '<', $file;
}

And it seems there is typo in $fn . Shouldn't it be $fh ?

Answer 4

Your understanding of open is incorrect. The modern way of using it with a three argument call is typically:

open my $fh, '<', <file name> or die $!;

You specify a new file handle object as the first argument, not the file name. You also do not need to open a file to check if it exists. So instead of doing that just do something along the lines of:

my $file = 'words.txt';
if (! -e $file) {
  print "$file does not exist\n";
}
else {
 # open your file here and remember to close it
}

Then just use the special diamond operator <> to operate on STDIN if it does not exist.