Question

Below code is the part of the script, in which I am merging files of different directories. After merging I am copying remaining files into final directory.
Merging is working fine but while copying files I am getting

cp: missing destination file operand after `/users/abc/perl_scripts/temp_dir/b.cc'
Try `cp --help' for more information.
sh: line 1: /users/abc/perl_scripts/temp: is a directory

for $k(dir1) {
     $flag=0;
     for $j(@dir2) {
          if("$k" eq "$j") {
               &merge_gcov("$UERRC1/$k","$UERRC2/$k","$DATA_DIR/$k");
               $flag=1;
               last;                            
          }
     }
     if($flag == 0) {
           #print ">>>>>>>>>>>>> cp $UERRC1/$k $DATA_DIR/$k \n";
           'cp $UERRC1/$k,$DATA_DIR`;
     }
 }

Can anybody help me to resolve this…

Answer 1

Whenever you are using system calls you are most likely doing something redundant, and it certainly is redundant in this case. Perl is very capable of copying files. I recommend the File::Copy module, which is a core module in perl 5. Using it is simple:

use File::Copy qw(copy);
copy $from, $to or die $!;   # it is a good idea to check if the copy failed

Also, instead of looping over all the file names in @dir2 and see if the name matches the one in $k, why not just check if the file exists in the other directory? E.g.

if (-e "$UERRC1/$k") {    # check if file exists
    merge_gcov("$UERRC1/$k", "$UERRC2/$k", "$DATA_DIR/$k"); 
} else { 
    copy "$UERRC1/$k", $DATA_DIR or die $!; 
}

The documentation for the file test -e is found in perldoc -f "-X"

You really should use variable names that are more appropriate. It will make your code more readable and much easier to maintain and debug.

Also…

Before you do anything else, you should add the following two lines to your script and fix the errors that undoubtedly appear:

use strict;
use warnings;

strict will force you to declare all variables (typically with my $foo) which will remove hard to detect bugs due to typos in variable names. The error message will read “Global symbol $foo requires explicit package name …”.

warnings will give you information about things that you are doing wrong. This is a good thing.