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GETLOGIN(2)                 BSD System Calls Manual                GETLOGIN(2)

NAME
     getlogin, setlogin -- get/set login name

SYNOPSIS
     #include <unistd.h>

     char *
     getlogin(void);

     int
     setlogin(const char *name);

DESCRIPTION
     The getlogin() routine returns the login name of the user associated with the current session, as pre-viously previously
     viously set by setlogin().  The name is normally 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 invoked).

RETURN VALUES
     If a call to getlogin() succeeds, it returns a pointer to a null-terminated 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.

ERRORS
     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 super-user.

SEE ALSO
     setsid(2)

BUGS
     Login names are limited in length by setlogin().  However, lower limits are placed on login names else-where elsewhere
     where in the system (UT_NAMESIZE in <utmp.h>).

     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.

HISTORY
     The getlogin() function first appeared in 4.4BSD.

4.2 Berkeley Distribution        June 9, 1993        4.2 Berkeley Distribution

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