---
name: "OpenBSD::RequiredBy"
section: "3p"
platform: "openbsd"
package: "man"
version: "8.0-current-20261101"
release: "OpenBSD 8.0-current (2026-11-01)"
platforms: ["openbsd"]
url: "https://new.carta.tech/OpenBSD::RequiredBy"
---

# OpenBSD::RequiredBy(3p)

manage installed package dependencies

## NAME

OpenBSD::RequiredBy - manage installed package dependencies

## SYNOPSIS

```
    use OpenBSD::RequiredBy;
    # let's do things for real
    our $not = 0;
    my $o = OpenBSD::RequiredBy->new($pkgname);
    my $o2 = OpenBSD::Requiring->new($pkgname);
    print "Requirements for $pkgname are ", join(' ',$o2->list), "\n";
    # add some reverse dependencies
    $o->add($reverse_dep1, $reverse_dep2);
    # remove some dependency
    $o2->delete($dep);
    # forget some cache entry
    OpenBSD::RequiredBy->forget(installed_info($pkgname));
    # compute the transitive closure of some dependencies
    my @fulldeps = OpenBSD::Requiring->compute_closure($pkg1, $pkg2);
```

## DESCRIPTION

`"OpenBSD::RequiredBy"` handles lists of forward and reverse dependencies for installed packages.

If `$main::not` is true, all change operations are done internally and never written to disk.

`"$o = OpenBSD::RequiredBy->new($pkgname)"` gives access to the reverse dependencies, `"$o =OpenBSD::Requiring->new($pkgname)"`  gives access to the forward dependencies.

Such an object can be used to list the dependencies `"$o->list"`, add names to them `"$o->add(name1, name2, ...)"` or remove name from them `"$o->delete(name1, name2, ...)"`.

The full list of forward dependencies (transitive closure) from a set of packages is given by `"OpenBSD::RequiredBy->compute_closure($name1, name2, ...)"`. Likewise, `"OpenBSD::Requiring->compute_closure($name1, name2, ...)"` yields the list of reverse dependencies.

Those lists of dependencies trim duplicates and, unless `$main::not` is true, disk files are automatically synchronized whenever the lists change.

`"OpenBSD::RequiredBy"` maintains a cache for efficiency. When an installed package is deleted completely, `"OpenBSD::RequiredBy->forget($dir)"` and `"OpenBSD::Requiring->forget($dir)"` will remove the cache entries.