euidaccess, eaccess - check effective user's permissions for a file

       For an explanation of the terms used in this section, see attributes(7).
       ┌─────────────────────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                                                                   │ Attribute     │ Value   │
       ├─────────────────────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │ euidaccess(), eaccess()                                                     │ Thread safety │ MT-Safe │
       └─────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

       Like  access(2),  euidaccess()  checks  permissions  and existence of the file identified by its argument
       pathname.  However, whereas access(2) performs checks using the real user and group  identifiers  of  the
       process, euidaccess() uses the effective identifiers.

       mode  is  a  mask  consisting of one or more of R_OK, W_OK, X_OK, and F_OK, with the same meanings as for
       access(2).

       eaccess() is a synonym for euidaccess(), provided for compatibility with some other systems.

       As for access(2).

eaccess()
              glibc 2.4.

       Standard C library (libc, -lc)

       euidaccess, eaccess - check effective user's permissions for a file

Warning:  Using this function to check a process's permissions on a file before performing some operation
       based on that information leads to race conditions: the file  permissions  may  change  between  the  two
       steps.  Generally, it is safer just to attempt the desired operation and handle any permission error that
       occurs.

       This  function  always  dereferences  symbolic links.  If you need to check the permissions on a symbolic
       link, use faccessat(2) with the flags AT_EACCESS and AT_SYMLINK_NOFOLLOW.

       On success (all requested permissions granted), zero is returned.  On error (at least  one  bit  in  mode
       asked for a permission that is denied, or some other error occurred), -1 is returned, and errno is set to
       indicate the error.

access(2), chmod(2), chown(2), faccessat(2),  open(2),  setgid(2),  setuid(2),  stat(2),  credentials(7),
       path_resolution(7)

Linux man-pages 6.9.1                              2024-05-02                                      euidaccess(3)

       None.

#define_GNU_SOURCE             /* See feature_test_macros(7) */
       #include<unistd.h>inteuidaccess(constchar*pathname,intmode);inteaccess(constchar*pathname,intmode);

       Some other systems have an eaccess() function.