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GETLOGIN(2) UNIX Programmer's Manual GETLOGIN(2)
NNAAMMEE
ggeettllooggiinn, sseettllooggiinn - get/set login name
SSYYNNOOPPSSIISS
##iinncclluuddee <<uunniissttdd..hh>>
_c_h_a_r _*
ggeettllooggiinn(_v_o_i_d)
_i_n_t
sseettllooggiinn(_c_o_n_s_t _c_h_a_r _*_n_a_m_e)
DDEESSCCRRIIPPTTIIOONN
The ggeettllooggiinn() routine returns the login name of the user associated with
the current session, as previously set by sseettllooggiinn(). 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.)
SSeettllooggiinn() sets the login name of the user associated with the current
session to _n_a_m_e. This call is restricted to the superuser, and is nor
mally 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 in
voked).
RREETTUURRNN VVAALLUUEESS
If a call to ggeettllooggiinn() 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 sseettllooggiinn() succeeds, a value of 0 is returned.
If sseettllooggiinn() fails, a value of 1 is returned and an error code is
placed in the global location _e_r_r_n_o.
EERRRROORRSS
The following errors may be returned by these calls:
[EFAULT] The _n_a_m_e parameter gave an invalid address.
[EINVAL] The _n_a_m_e parameter pointed to a string that was too long.
Login names are limited to MAXLOGNAME (from <_s_y_s_/_p_a_r_a_m_._h>)
characters, currently 12.
[EPERM] The caller tried to set the login name and was not the su
peruser.
SSEEEE AALLSSOO
setsid(2)
BBUUGGSS
Login names are limited in length by sseettllooggiinn(). However, lower limits
are placed on login names elsewhere in the system (UT_NAMESIZE in
<_u_t_m_p_._h>).
In earlier versions of the system, ggeettllooggiinn() failed unless the process
was associated with a login terminal. The current implementation (using
sseettllooggiinn()) allows getlogin to succeed even when the process has no con
trolling terminal. In earlier versions of the system, the value returned
by ggeettllooggiinn() could not be trusted without checking the user ID.
Portable programs should probably still make this check.
HHIISSTTOORRYY
The ggeettllooggiinn function call is currently under development.