setreuid - set real and effective user IDs
#include <unistd.h> int setreuid(uid_t ruid, uid_t euid);
The setreuid() function sets the real and effective user IDs of the current process to the values specified by the ruid and euid arguments. If ruid or euid is -1, the corresponding effective or real user ID of the current process is left unchanged.
A process with appropriate privileges can set either ID to any value. An unprivileged process can only set the effective user ID if the euid argument is equal to either the real, effective, or saved user ID of the process.
It is unspecified whether a process without appropriate privileges is permitted to change the real user ID to match the current real, effective or saved user ID of the process.
Upon successful completion, 0 is returned. Otherwise, -1 is returned and errno is set to indicate the error.
The setreuid() function will fail if:
- The value of the ruid or euid argument is invalid or out-of-range.
- The current process does not have appropriate privileges, and either an attempt was made to change the effective user ID to a value other than the real user ID or the saved set-user-ID or an an attempt was made to change the real user ID to a value not permitted by the implementation.
getuid(), setuid(), <unistd.h>.