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32 .\" @(#)getlogin.2 8.1 (Berkeley) 6/9/93
42 .Nd get/set login name
51 .Fn getlogin_r "char *name" "int len"
53 .Fn setlogin "const char *name"
58 returns the login name of the user associated with the current session,
61 The name is normally associated with a login shell
62 at the time a session is created,
63 and is inherited by all processes descended from the login shell.
64 (This is true even if some of those processes assume another user ID,
70 provides the same service as
72 except the caller must provide the buffer
77 to hold the result. The buffer should be at least
82 sets the login name of the user associated with the current session to
84 This call is restricted to the super-user, and
85 is normally used only when a new session is being created on behalf
87 (for example, at login time, or when a remote shell is invoked).
90 There is only one login name per session.
94 important to ensure that
96 is only ever called after the process has taken adequate steps to ensure
97 that it is detached from its parent's session.
106 which is an ideal way of detaching from a controlling terminal and
107 forking into the background.
109 In particular, doing a
110 .Fn ioctl ttyfd TIOCNOTTY ...\&
117 Once a parent process does a
119 call, it is acceptable for some child of that process to then do a
121 even though it is not the session leader, but beware that ALL processes
122 in the session will change their login name at the same time, even the
125 This is not the same as the traditional UNIX behavior of inheriting privilege.
129 system call is restricted to the super-user, it is assumed that (like
130 all other privileged programs) the programmer has taken adequate
131 precautions to prevent security violations.
135 succeeds, it returns a pointer to a null-terminated string in a static buffer,
138 if the name has not been set.
140 returns zero if successful, or the error number upon failure.
144 The following errors may be returned by these calls:
155 pointed to a string that was too long.
156 Login names are limited to
159 .Ao Pa sys/param.h Ac )
160 characters, currently 17 including null.
162 The caller tried to set the login name and was not the super-user.
164 The size of the buffer is smaller than the result to be returned.
170 In earlier versions of the system,
172 failed unless the process was associated with a login terminal.
173 The current implementation (using
175 allows getlogin to succeed even when the process has no controlling terminal.
176 In earlier versions of the system, the value returned by
178 could not be trusted without checking the user ID.
179 Portable programs should probably still make this check.
183 function first appeared in
187 was changed from earlier versions of
189 to be conformant with