fast_abs_path#

Canonicalise a path strictly: resolve symlinks and ./.., or return undef if any component is missing.

Synopsis#

use Cwd qw(fast_abs_path);
my $abs = fast_abs_path($path);
my $abs = fast_abs_path();      # defaults to current directory

What you get back#

A plain Perl string with the absolute, symlink-free path, or undef if any part of the path cannot be resolved (including the leaf). Unlike abs_path, there is no parent-plus-leaf fallback — a missing final component is treated as an error.

Examples#

Verify that a path exists and get its canonical form in one step:

use Cwd qw(fast_abs_path);
my $abs = fast_abs_path('/etc/passwd');
defined $abs or die "not found: $!";
print $abs, "\n";                 # /etc/passwd

Reject non-existent files up front:

use Cwd qw(fast_abs_path);
print defined fast_abs_path('/no/such/file') ? "ok" : "missing";
    # missing

Resolve the current directory quickly:

use Cwd qw(fast_abs_path);
print fast_abs_path(), "\n";      # equivalent to getcwd()

Edge cases#

Empty string or no argument — treated as ..
Any missing component (including the leaf) — returns undef. Use abs_path when a missing leaf should still produce a path.
Symlink loop — returns undef and sets $! to ELOOP.

Differences from upstream#

Upstream’s fast_abs_path localises $ENV{PWD}, chdirs into the target, and reads the new CWD back. pperl calls canonicalize(3) directly — the result is the same, but the process working directory is never disturbed, so concurrent code that observes CWD sees no perturbation.