使用Perl检查〜/中是否存在目录

Question

I noticed strange behavior of the -d flag to check if a file is a directory and if the directory exists. It behaves differently when using ~/my_dir as my path.

The following code will return false, even though the directory my_dir exists, but if I'll change it to a full path like /home/ricky/my_dir , then the if statement will return true.

#!/usr/bin/perl -w
#
use strict;

if ( -d "~/my_dir") {
    print "Found \n";
}
else {
    print "Not found \n";
}

What's the difference?

Answer 1

~ is a shell shortcut to indicate the home directory, it is unknown to perl. You have to use the environment variable HOME here -- for instance using "$ENV{HOME}/my_dir" .

Answer 2

~ is not a real path. Shells such as /bin/bash expand it to the value of the $HOME environment variable. Perl does not. So, you should use something like this instead:

if ( -d "$ENV{HOME}/my_dir" ) {
    ...
}

Answer 3

You can check by executing the chdir command also. chdir "dir_name" will return 0, if directory is not present. And 1 if directory is present.