GETLOGIN(2) System Calls GETLOGIN(2)
getlogin, setlogin - get/set login name
char *getlogin (void);
int setlogin (const char *name);
The getlogin routine returns the login name of the user associated with
the current session, as previously set by setlogin. The name is nor-
mally associated with a login shell at the time a session is created,
and is inherited by all processes descended from the login shell.
(This is true even if some of those processes assume another user ID,
for example when su(1) is used.)
Setlogin sets the login name of the user associated with the current
session to name. This call is restricted to the super-user, and is
normally used only when a new session is being created on behalf of the
named user (for example, at login time, or when a remote shell is
If a call to getlogin succeeds, it returns a pointer to a null-termi-
nated string in a static buffer. If the name has not been set, it
returns NULL. If a call to setlogin succeeds, a value of 0 is
returned. If setlogin fails, a value of -1 is returned and an error
code is placed in the global location errno.
The following errors may be returned by these calls:
EFAULT The name parameter gave an invalid address.
EINVAL The name parameter pointed to a string that was too long.
Login names are limited to MAXLOGNAME (from
<sys/param.h>) characters, currently 12.
EPERM The caller tried to set the login name and was not the
Login names are limited in length by setlogin. However, lower limits
are placed on login names elsewhere in the system (UT_NAMESIZE in
In earlier versions of the system, getlogin failed unless the process
was associated with a login terminal. The current implementation
(using setlogin) allows getlogin to succeed even when the process has
no controlling terminal. In earlier versions of the system, the value
returned by getlogin could not be trusted without checking the user ID.
Portable programs should probably still make this check.
The getlogin function first appeared in 4.4BSD.
GNO 17 September 1997 GETLOGIN(2)
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