setresuid, setresgid - set real, effective and saved user or group ID


#define _GNU_SOURCE
#include <unistd.h>

int setresuid(uid_t ruid, uid_t euid, uid_t suid);
int setresgid(gid_t rgid, gid_t egid, gid_t sgid);


setresuid() sets the real user ID, the effective user ID, and the saved set-user-ID of the calling process.

Unprivileged user processes may change the real UID, effective UID, and saved set-user-ID, each to one of: the current real UID, the current effective UID or the current saved set-user-ID.

Privileged processes (on Linux, those having the CAP_SETUID capability) may set the real UID, effective UID, and saved set-user-ID to arbitrary values.

If one of the arguments equals -1, the corresponding value is not changed.

Regardless of what changes are made to the real UID, effective UID, and saved set-user-ID, the file system UID is always set to the same value as the (possibly new) effective UID.

Completely analogously, setresgid() sets the real GID, effective GID, and saved set-group-ID of the calling process (and always modifies the file system GID to be the same as the effective GID), with the same restrictions for non-privileged processes.


On success, zero is returned. On error, -1 is returned, and errno is set appropriately.


uid does not match the current UID and this call would bring that user ID over its RLIMIT_NPROC resource limit.
The calling process is not privileged (did not have the CAP_SETUID capability) and tried to change the IDs to values that are not permitted.


These calls are available under Linux since Linux 2.1.44.


These calls are non-standard; they also appear on HP-UX and some of the BSDs.


Under HP-UX and FreeBSD the prototype is found in <unistd.h>. Under Linux the prototype is provided by glibc since version 2.3.2.


getresuid(2), getuid(2), setfsgid(2), setfsuid(2), setreuid(2), setuid(2), capabilities(7), credentials(7), feature_test_macros(7)


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