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32 .\" @(#)getlogin.2 8.1 (Berkeley) 6/9/93
41 .Nd get/set login name
43 .Fd #include <unistd.h>
47 .Fn setlogin "const char *name"
52 returns the login name of the user associated with the current session,
55 The name is normally associated with a login shell
56 at the time a session is created,
57 and is inherited by all processes descended from the login shell.
58 (This is true even if some of those processes assume another user ID,
64 sets the login name of the user associated with the current session to
66 This call is restricted to the super-user, and
67 is normally used only when a new session is being created on behalf
69 (for example, at login time, or when a remote shell is invoked).
72 There is only one `login name' per `session .
76 important to ensure that
78 is only ever called after the process has taken adequate steps to ensure
79 that it is detached from its parent's session.
88 which is an ideal way of detaching from a controlling terminal and
89 forking into the background.
91 In particular, doing a
92 .Fn ioctl ttyfd TIOCNOTTY ...
99 Once a parent process does a
101 call, it is acceptable for some child of that process to then do a
103 even though it is not the session leader, but beware that ALL processes
104 in the session will change their login name at the same time, even the
107 This is not the same as the traditional UNIX behavior of inheriting privilege.
111 system call is restricted to the super-user, it is assumed that (like
112 all other privileged programs) the programmer has taken adequate
113 precautions to prevent security violations.
117 succeeds, it returns a pointer to a null-terminated string in a static buffer.
118 If the name has not been set, it returns
122 succeeds, a value of 0 is returned. If
124 fails, a value of -1 is returned and an error code is
125 placed in the global location
128 The following errors may be returned by these calls:
139 pointed to a string that was too long.
140 Login names are limited to
143 .Ao Pa sys/param.h Ac )
144 characters, currently 17 including null.
146 The caller tried to set the login name and was not the super-user.
152 In earlier versions of the system,
154 failed unless the process was associated with a login terminal.
155 The current implementation (using
157 allows getlogin to succeed even when the process has no controlling terminal.
158 In earlier versions of the system, the value returned by
160 could not be trusted without checking the user ID.
161 Portable programs should probably still make this check.
165 function first appeared in