UNIX Shell: Find Out Real Path Of File or Directory

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My programs and scripts needs a real path and not a a symbolic link. How to I determine a real path of any directory under Linux / UNIX like operating systems? How do I remove references to /./, /../ and extra ‘/’ character in path?

To get physical path use realpath command. The realpath command uses the realpath() function to resolve all symbolic links, extra / characters and references to /./ and /../ in path. This is useful for shell scripting and security related applications.

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Another option is readlink command to print value of a symbolic link or canonical file name.

Finally, you can use Perl or Python to print value of a symbolic link or canonical file name.

realpath examples

To resolve symbolic link, type:
$ realpath /home
Sample outputs:

/usr/home

To remove characters, run:
$ realpath /etc//apache/.
$ realpath ./foo
$ realpath /../some/where///./../path/

The realpath command included with most Linux distributions and UNIX like operating system such as FreeBSD. To install realpath under Debian / Ubuntu Linux, enter:
$ sudo apt-get install realpath

readlink command

Please note that mostly the same functionality is provided by the -f option of the readlink command:
$ readlink -f /home

Perl program example

Try the following Perl code for portability purpose under various Linux and Unix like oses:

#!/usr/bin/perl
use Cwd 'abs_path';
if (@ARGV != 2 ) {
  print "Usage: $0 --path file\n";
  exit;
}
$realfilepath = abs_path("$ARGV[1]");
print "$realfilepath\n";

Sample outputs:

Fig.01: Perl program in action
Fig.01: Perl program in action

Recommended readings:
  • man pages: readlink and realpath
  • To see Cwd document type: perldoc Cwd

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Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin, DevOps engineer, and a trainer for the Linux operating system/Unix shell scripting. Get the latest tutorials on SysAdmin, Linux/Unix and open source topics via RSS/XML feed or weekly email newsletter.


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12 comment

  6. realpath and even reallink are NOT generally available on all linux machines (most unusual). It is certainally not available on solaris or other OS’s.

    And yet the C library provides a “realpath” function, it is just not generally available to shell scripts. And my shell scripts generally have to deal with multiple OS environments.

    So lets repeat the question…

    How can you get the real path of a file with all symbolic links resolved on MOST unix operating systems. Is some special switch to some command available? Is there a drop in shell function that can be used?

    Reply

    1. Try:

      #!/usr/bin/perl
use Cwd 'abs_path';
if (@ARGV != 2 ) {
  print "Usage: $0 --path file\n";
  exit;
}
$realfilepath = abs_path("$ARGV[1]");
print "$realfilepath\n";

      Run it as:

      ./myrealpath.pl --path /foo/bar
./myrealpath.pl --path ../foo/bar
./myrealpath.pl --path ~/bar
./myrealpath.pl --path /path/to/dir
      Reply

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