ACL_GET_PERM(3)

💅 ACL_GET_PERM — bestie's guide to peeking at permissions

okay so this is a page from ACL_GET_PERM(3), aka section 3 of the Library Functions Manual, and it's literally just "does this permission set contain this one permission?" no cap. it's giving tiny function, huge main character energy. let's go 🦋

✨ NAME ✨

acl_get_perm — test for a permission in an ACL permission set 💖

📚 LIBRARY 📚

Linux Access Control Lists library (libacl, link it with -lacl) — yeah bestie, you gotta bring the library to the party 🎀

🌸 SYNOPSIS 🌸

#include <sys/types.h>
#include <acl/libacl.h>

int
acl_get_perm(acl_permset_t permset_d, acl_perm_t perm);

look at that signature. so clean. so iconic. ✨

💫 DESCRIPTION 💫

so the acl_get_perm() function does one (1) job and she does it well: she tests whether the permission you named in the argument perm is contained in the ACL permission set pointed to by the argument permset_d.

and what even is perm allowed to be, you ask? it's one of ACL_READ, ACL_WRITE, ACL_EXECUTE. those three. that's the whole menu. 💅

and here's the cute part — any existing descriptors that refer to permset_d continue to refer to that permission set. nothing gets yanked out from under you. she's stable. she's loyal. 🫶

🎀 RETURN VALUE 🎀

if it works out (and it will, bestie), acl_get_perm() returns:

• 1 — yesss, the permission specified by perm is contained in the ACL permission set permset_d ✅
• 0 — nope, that permission is not contained in the permission set 🙈

otherwise, the value -1 is returned and the global variable errno gets set to indicate the error. sad girl hours. 😭

💀 ERRORS 💀

if any of the following conditions occur, acl_get_perm() returns -1 and sets errno to the corresponding value — read these, fr fr, don't skip:

• [EINVAL] — the argument permset_d is not a valid descriptor for a permission set within an ACL entry. or the argument perm is not a valid acl_perm_t value. two ways to fail this vibe check, pick neither. ⚠️

ngl, EINVAL is just the universe saying "that's not a real thing, babe."

🌈 STANDARDS 🌈

this is a non-portable, Linux specific extension to the ACL manipulation functions defined in IEEE Std 1003.1e draft 17 ("POSIX.1e", abandoned). yes, abandoned. we don't talk about it. 💀

so like, don't expect your BSD bestie's system to know what you're talking about. this is a Linux-only slay.

👑 SEE ALSO 👑

go read her friends, they're all icons:

• acl_add_perm(3)
• acl_clear_perms(3)
• acl_delete_perm(3)
• acl_get_permset(3)
• acl_set_permset(3)
• acl(5)

🧚 AUTHOR 🧚

written by Andreas Gruenbacher <andreas.gruenbacher@gmail.com>. thank you for your service, king 🫡💜

and that's the whole page, bestie!! 🌸 this was the Linux ACL manual page for acl_get_perm(3), dated March 23, 2002, from the Linux ACL source. go forth and check those permissions, periodt. 💅✨🦋🎀