> Thomas Burkhardt <[EMAIL PROTECTED]> said:
> Greetings Perl Gurus!
> Using Perl, how do count the number of lines in a given file?
>
> I know how to run the code:
>
> open(MYPIPE, "|wc -l");
> print MYPIPE "apples\npears\npeaches\n";
> close MYPIPE;
If you want to simply print the number of lines in a file, you can do it with
the system() function. e.g.
system("wc -l $filename");
If you want to count the lines without help from the "wc" program, it looks
like:
my $filename = "/etc/passwd";
my $count = 0;
open(IN, "<$filename") || die "cannot open $filename - $!\n";
while (<IN>) {
$count++;
}
close IN;
print "$count\n";
Now if you want to open a file and shove it thru a filter it looks like:
my $filename = "/etc/passwd";
open(IN, "<$filename") || die "cannot open $filename - $!\n";
open(PIPE, "| wc -l") || die "cannot open pipe - $!\n";
while (<IN>) {
print PIPE;
}
close IN;
close PIPE;
Note you can do this by slurping the entire file into an array, but that uses
up memory with large files. This version looks like:
my $filename = "/etc/passwd";
open(IN, "<$filename") || die "cannot open $filename - $!\n";
open(PIPE, "| wc -l") || die "cannot open pipe - $!\n";
print PIPE <IN>;
close IN;
close PIPE;
I prefer to read files line by line unless there is a specific reason to bring
the entire file into memory.
--
Smoot Carl-Mitchell
Consultant
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