SETRESUID(2)                        Linux Programmer's Manual                        SETRESUID(2)



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

SYNOPSIS
       #define _GNU_SOURCE         /* See feature_test_macros(7) */
       #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);

DESCRIPTION
       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 filesystem 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 filesystem GID to be the same as the
       effective GID), with the same restrictions for unprivileged processes.

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

       Note: there are cases where setresuid() can fail even when the caller is UID 0;  it  is  a
       grave security error to omit checking for a failure return from setresuid().

ERRORS
       EAGAIN The call would change the caller's real UID (i.e., ruid does not match the caller's
              real UID), but there was a temporary failure allocating the necessary  kernel  data
              structures.

       EAGAIN ruid  does  not match the caller's real UID and this call would bring the number of
              processes belonging to the  real  user  ID  ruid  over  the  caller's  RLIMIT_NPROC
              resource  limit.   Since  Linux  3.1,  this error case no longer occurs (but robust
              applications should check for  this  error);  see  the  description  of  EAGAIN  in
              execve(2).

       EINVAL One or more of the target user or group IDs is not valid in this user namespace.

       EPERM  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.

VERSIONS
       These calls are available under Linux since Linux 2.1.44.

CONFORMING TO
       These calls are nonstandard; they also appear on HP-UX and some of the BSDs.

NOTES
       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.

       The original Linux setresuid() and setresgid() system calls supported only 16-bit user and
       group IDs.  Subsequently, Linux 2.4  added  setresuid32()  and  setresgid32(),  supporting
       32-bit  IDs.   The  glibc setresuid() and setresgid() wrapper functions transparently deal
       with the variations across kernel versions.

SEE ALSO
       getresuid(2),  getuid(2),  setfsgid(2),  setfsuid(2),  setreuid(2),  setuid(2),  capabili‐
       ties(7), credentials(7), user_namespaces(7)

COLOPHON
       This  page  is  part of release 3.74 of the Linux man-pages project.  A description of the
       project, information about reporting bugs, and the latest version of  this  page,  can  be
       found at http://www.kernel.org/doc/man-pages/.



Linux                                       2014-09-21                               SETRESUID(2)