setresuid(2)

1SETRESUID(2)               Linux Programmer's Manual              SETRESUID(2)
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NAME

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

9       #define _GNU_SOURCE
10       #include <unistd.h>
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12       int setresuid(uid_t ruid, uid_t euid, uid_t suid);
13       int setresgid(gid_t rgid, gid_t egid, gid_t sgid);
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DESCRIPTION

16       setresuid() sets the real user ID, the effective user ID, and the saved
17       set-user-ID of the current process.
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19       Unprivileged user processes may change the real UID, effective UID, and
20       saved  set-user-ID,  each  to one of: the current real UID, the current
21       effective UID or the current saved set-user-ID.
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23       Privileged processes (on Linux, those having the CAP_SETUID capability)
24       may set the real UID, effective UID, and saved set-user-ID to arbitrary
25       values.
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27       If one of the parameters equals -1,  the  corresponding  value  is  not
28       changed.
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30       Regardless of what changes are made to the real UID, effective UID, and
31       saved set-user-ID, the file system UID is always set to the same  value
32       as the (possibly new) effective UID.
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34       Completely  analogously,  setresgid() sets the real GID, effective GID,
35       and saved set-group-ID of the current process (and always modifies  the
36       file  system  GID  to  be the same as the effective GID), with the same
37       restrictions for non-privileged processes.
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RETURN VALUE

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

45       EAGAIN uid  does  not  match  the current UID and this call would bring
46              that user ID over its NPROC rlimit.
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48       EPERM  The  calling  process  is  not  privileged  (did  not  have  the
49              CAP_SETUID  capability)  and  tried  to change the IDs to values
50              that are not permitted.
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CONFORMING TO

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

57       This  system call was first introduced in HP-UX.  It is available under
58       Linux since Linux 2.1.44.  These days it is also found in FreeBSD  (for
59       emulation of Linux binaries).
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NOTES

62       Under  HP-UX  and  FreeBSD the prototype is found in <unistd.h>.  Under
63       Linux the prototype is given by  glibc  since  version  2.3.2  provided
64       _GNU_SOURCE is defined.
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