1setuid(2) System Calls setuid(2)
2
6 setuid, setegid, seteuid, setgid - set user and group IDs
7
9 #include <sys/types.h>
10 #include <unistd.h>
11 int setuid(uid_t uid);
13 int setgid(gid_t gid);
16 int seteuid(uid_t euid);
19 int setegid(gid_t egid);
22
25 The setuid() function sets the real user ID, effective user ID, and
26 saved user ID of the calling process. The setgid() function sets the
27 real group ID, effective group ID, and saved group ID of the calling
28 process. The setegid() and seteuid() functions set the effective group
29 and user IDs respectively for the calling process. See Intro(2) for
30 more information on real, effective, and saved user and group IDs.
31 At login time, the real user ID, effective user ID, and saved user ID
34 of the login process are set to the login ID of the user responsible
35 for the creation of the process. The same is true for the real, effec‐
36 tive, and saved group IDs; they are set to the group ID of the user
37 responsible for the creation of the process.
38 When a process calls one of the exec(2) family of functions to execute
41 a file (program), the user and/or group identifiers associated with the
42 process can change. If the file executed is a set-user-ID file, the
43 effective and saved user IDs of the process are set to the owner of the
44 file executed. If the file executed is a set-group-ID file, the effec‐
45 tive and saved group IDs of the process are set to the group of the
46 file executed. If the file executed is not a set-user-ID or set-group-
47 ID file, the effective user ID, saved user ID, effective group ID, and
48 saved group ID are not changed.
49 If the {PRIV_PROC_SETID} privilege is asserted in the effective set of
52 the process calling setuid(), the real, effective, and saved user IDs
53 are set to the uid argument. If the uid argument is 0 and none of the
54 saved, effective or real UID is 0, additional restrictions apply. See
55 privileges(5).
56 If the {PRIV_PROC_SETID} privilege is not asserted in the effective
59 set, but uid is either the real user ID or the saved user ID of the
60 calling process, the effective user ID is set to uid.
61 If the {PRIV_PROC_SETID} privilege is asserted in the effective set of
64 the process calling setgid(), the real, effective, and saved group IDs
65 are set to the gid argument.
66 If the {PRIV_PROC_SETID} privilege is not asserted in the effective
69 set, but gid is either the real group ID or the saved group ID of the
70 calling process, the effective group ID is set to gid.
71
73 Upon successful completion, 0 is returned. Otherwise, −1 is returned
74 and errno is set to indicate the error.
75
77 The setuid() and setgid() functions will fail if:
78 EINVAL The value of uid or gid is out of range.
80 EPERM For setuid() and seteuid(), the {PRIV_PROC_SETID} privilege
83 is not asserted in the effective set of the calling process
84 and the uid argument does not match either the real or saved
85 user IDs, or an attempt is made to change to UID 0 and none
86 of the existing UIDs is 0, in which case additional privi‐
87 leges are required.
88 For setgid() and setegid(), the {PRIV_PROC_SETID} privilege
90 is not asserted in the effective set and the gid argument
91 does not match either the real or saved group IDs.
92
95 See attributes(5) for descriptions of the following attributes:
96 ┌─────────────────────────────┬─────────────────────────────┐
101 │ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
102 ├─────────────────────────────┼─────────────────────────────┤
103 │Interface Stability │Standard │
104 ├─────────────────────────────┼─────────────────────────────┤
105 │MT-Level │Async-Signal-Safe │
106 └─────────────────────────────┴─────────────────────────────┘
107
109 Intro(2), exec(2), getgroups(2), getuid(2), stat.h(3HEAD),
110 attributes(5), privileges(5), standards(5)
111SunOS 5.11 20 Jan 2003 setuid(2)