How to copy file content to another file in Perl

Perl comes with a core module called File::Copy that allows two essential functions, namely:

Copy
Move

These functions serve to transfer the contents of a file from one place to another. But what matters for us is the copy method which has the following syntax:

copy(source_file, destination_file)

This command accepts two parameters:

source_file: A FileHandle reference, a FileHandle glob, or a string representing the path to the source file is used in this argument.
destination_file: A FileHandle reference, a FileHandle glob, or a string representing the path to the destination file is used in this argument.

Note: The destination file will be created automatically if it does not exist but its parent directory exists. An error will occur when copying to a nonexistent directory.

Let's get into the coding and check the following examples:

Code example 1

This example shows how to copy file content while using the inbuilt copy function previously described:

main.perl

input.txt

$input_file = 'input.txt';
$output_file = '/usercode/output/output.txt';
open(input , "< $input_file") or die "Unable to open $input_file";
open(output, "> $output_file") or die "Unable to open $output_file";
$v_blk_size = (stat input)[11] || 16384;          
while ($v_len = sysread input, $v_buf, $v_blk_size) {
    if (!defined $v_len) {
        next if $! =~ /^Interrupted/;      
        die "Error System Read: $!\n";
    }
    $v_offset = 0;
    while ($v_len) {          # Handle partial writes.
        defined($written = syswrite output, $v_buf, $v_len, $v_offset)
            or die "Error System Write: $!\n";
        $v_len    -= $written;
        $v_offset += $written;
    };
}
close(input);
close(output);

Let's go through the code widget, as follows:

Line 1: Define a variable, $input_file, pointing to the source file.
Line 2: Define a variable, $output_file, containing the destination file path.
Line 4: Open the source file using the function open, as follows:
- The operand < indicates that this file is opened in read-only mode.
- The function returns a FileHandle in associated with the source file.
  File-opening failures are handled using the die function.
Line 5: By the same token, open the destination file in write-only mode (operand >).
Line 7: Set the preferred block size for file system I/O.
Lines 8–20: Loop through the content blocks of the source file and write them to the destination file. We may exit the process by pressing CTRL-Z.
Line 22: Close the source FileHandle.
Line 23: Close the destination FileHandle.

How to copy file content to another file in Perl

Code example 1

Code example 2