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getuid, geteuid — get user identification
Standard C Library (libc, -lc)
#include <unistd.h> uid_t getuid(void); uid_t geteuid(void);
The getuid() system call returns the real user ID of the calling process. The geteuid() system call returns the effective user ID of the calling process. The real user ID is that of the user who has invoked the program. As the effective user ID gives the process additional permissions during execution of “set-user-ID” mode processes, getuid() is used to determine the real-user-id of the calling process.
The getuid() and geteuid() system calls are always successful, and no return value is reserved to indicate an error.
The geteuid() and getuid() system calls are expected to conform to ISO/IEC 9945-1:1990 (“POSIX.1”).
The getuid() function appeared in Version 1 AT&T UNIX. The geteuid() function appeared in Version 4 AT&T UNIX.