Technical Reference: Kernel and Subsystems, Volume 1

suser Kernel Service

Determines the privilege state of a process.

#include <sys/types.h>
#include  <sys/errno.h>

int suser ( ep) char *ep;

ep	Points to a character variable where the EPERM value is stored on failure.

The suser kernel service checks whether a process has any effective privilege (that is, whether the process's uid field equals 0).

The suser kernel service can be called from the process environment only.

0	Indicates failure. The character pointed to by the ep parameter is set to the value of EPERM. This indicates that the calling process does not have any effective privilege.
Nonzero value	Indicates success (the process has the specified privilege).

Security Kernel Services in AIX 5L Version 5.2 Kernel Extensions and Device Support Programming Concepts.