在級聯

Question

使用未初始化值誤差從下面的代碼中，我得到錯誤

Use of uninitialized value $fileName in concatenation <.> or string at ... line 8. 

我也得到錯誤

Can't open from: No such file or directory at ... line 8. 

這是功課參考示例代碼。我試圖理解它。

use strict; 
use warnings; 

my $dayLength = $ARGV[0]; 
my $byteLength = $ARGV[1]; 
my $fileName = $ARGV[2]; 

open INPUT, "< $fileName" or die "Can't open from: $!"; 
my $takeIn = <INPUT>; 

print "$takeIn\n"; 

my @files = split//, $takeIn; 


print "@files\n"; 



foreach my $file (@files){ 
if(-M $file > $dayLength && -s $file > $byteLength){ 
print "\n::::::::$file::::::::\n"; 
open INPUT, "< $file" or die "Can't open from: $!"; 
my $i = <INPUT>; 
while($i = <INPUT>){ 
print $i;} 
    }} 

Answer 1

正如亨特提到的，它似乎沒有第三個參數，$ fileName沒有設置。

嘗試在open（）調用之前添加它以確保用戶提供文件名。

if (!defined($filename) or length($filename) == 0)) 
{ 
    die "filename argument is required"; 
}