#mode operand create truncate
#read < 
#write >  yes yes 
#append >> yes

Case 1: Throw an exception if you cannot open the file:

复制代码代码如下:


use strict;
use warnings;
 
my $filename = 'data.txt';
open(my $fh, '<:encoding(UTF-8)', $filename)
or die "Could not open file '$filename' with the error $!";
 
while (my $row = <$fh>) {
chomp $row;
print "$row\n";
}
close($fh);

  


Case 2: Give a warning if you cannot open the file, but keep running:

复制代码代码如下:


use strict;
use warnings;
 
my $filename = 'data.txt';
if (open(my $fh, '<:encoding(UTF-8)', $filename)) {
while (my $row = <$fh>) {
chomp $row;
print "$row\n";
}
close($fh);
} else {
warn "Could not open file '$filename' $!";
}

  


Case 3: Read one file into array

复制代码代码如下:


use strict;
use warnings;
 
my $filename = 'data.txt';
open (FILEIN, "<", $filename) 
or die "Could not open file '$filename' with the error $!";
my @FileContents = <FILEIN>;
for my $l (@FileContents){
print "$l\n";
}
close FILEIN;

  


end