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:
This example shows how to copy file content while using the inbuilt copy function previously described:
use File::Copy;$input_file = 'input.txt';$output_file = '/usercode/output/output.txt';copy($input_file, $output_file);
Let's go through the code widget, as follows:
Line 1: Import the standard File::Copy module.
Line 2: Define a variable, $input_file, pointing to the source file.
Line 3: Define a variable, $output_file, containing the destination file path.
Line 4: Invoke the function copy in order to get the source file content to the destination file.
The example below demonstrates how to perform the copy of the source file content while relying on low-level I/O routines:
$input_file = 'input.txt';$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.
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