I would like to parse in input file using command line. I ran as below but I am getting error (could not open filename) when I ran as below: Is my code wrong or what I type on the commandline is incorrect?
commandline> perl script.pl FILENAME1.TXT
Below is my code to parse in input file:
my $filename = <STDIN>;
open (my $file, '<', $filename) or die "could not open file '$filename': $!";
my $str = do {local $/; <$file>};
close $file;
You're trying to read $filename from standard input, when it's an argument to the program. You probably want something like
my $filename = $ARGV[0]
Perl's command line arguments show up in the variable @ARGV.
my( $filename ) = @ARGV;
However, Perl also has the special ARGV filehandle the opens the files you specify on the command line
while( <ARGV> ) { ... }
Even better, ARGV is the default filehandle:
while( <> ) { ... }
And, ARGV includes standard input if you didn't specify any arguments. That means that last while works in either of these calls:
% perl script.pl filename.txt
% perl script.pl < filename.txt
In your program, you read from STDIN, which is a different thing. That's standard input and is not related to the command line arguments. That's the data you send to the program after its running. For example, you might prompt for the filename:
print "Enter the filename: ";
my $filename = <STDIN>;
chomp( $filename );