setresuid(2) -- Linux man page
NAMEsetresuid, setresgid - set real, effective and saved user or group ID
DESCRIPTIONsetresuid sets the real user ID, the effective user ID, and the saved (effective) user ID of the current process.
Unprivileged user processes (i.e., processes with each of real, effective and saved user ID nonzero) may change the real, effective and saved user ID, each to one of: the current uid, the current effective uid or the current saved uid.
The super-user may set real, effective and saved user ID to arbitrary values.
If one of the parameters equals -1, the corresponding value is not changed.
Completely analogously, setresgid sets the real, effective and saved group ID's of the current process, with the same restrictions for processes with each of real, effective and saved user ID nonzero.
RETURN VALUEOn success, zero is returned. On error, -1 is returned, and errno is set appropriately.
- The current process was not privileged (did not have the CAP_SETUID capability) and tried to change the IDs is a not allowed way.
- uid does not match the current uid and this call would bring that userID over its NPROC rlimit.
CONFORMING TOThis call is nonstandard.
HISTORYThis system call was first introduced in HP-UX. It is available under Linux since Linux 2.1.44. These days it is also found in FreeBSD (for emulation of Linux binaries).
NOTESUnder HP-UX and FreeBSD the prototype is found in <unistd.h>. Under Linux the prototype is given by glibc since version 2.3.2 provided _GNU_SOURCE is defined.
SEE ALSOgetuid(2), setuid(2), setreuid(2), getresuid(2)