View Source: cuserid(3) - Waikato Linux Users Group

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GETLOGIN
!!!GETLOGIN
NAME
SYNOPSIS
DESCRIPTION
ERRORS
FILES
CONFORMING TO
BUGS
SEE ALSO
----
!!NAME


getlogin, cuserid - get user name
!!SYNOPSIS


__#include __


__char * getlogin ( void );__


__#include __


__char * cuserid ( char *__''string''
__);__
!!DESCRIPTION


__getlogin__ returns a pointer to a string containing the
name of the user logged in on the controlling terminal of
the process, or a null pointer if this information cannot be
determined. The string is statically allocated and might be
overwritten on subsequent calls to this function or to
__cuserid__.


__cuserid__ returns a pointer to a string containing a
user name associated with the effective user ID of the
process. If ''string'' is not a null pointer, it should
be an array that can hold at least __L_cuserid__
characters; the string is returned in this array. Otherwise,
a pointer to a string in a static area is returned. This
string is statically allocated and might be overwritten on
subsequent calls to this function or to
__getlogin__.


The macro __L_cuserid__ is an integer constant that
indicates how long an array you might need to store a user
name. __L_cuserid__ is declared in
__stdio.h__.


These functions let your program identify positively the
user who is running (__cuserid__) or the user who logged
in this session (__getlogin__). (These can differ when
setuid programs are involved.)


For most purposes, it is more useful to use the environment
variable __LOGNAME__ to find out who the user is. This is
more flexible precisely because the user can set
__LOGNAME__ arbitrarily.
!!ERRORS


__ENOMEM__


Insufficient memory to allocate passwd
structure.
!!FILES


''/etc/passwd''    password database file
''/var/run/utmp''  (traditionally ''/etc/utmp'';
some libc versions used ''/var/adm/utmp'')
!!CONFORMING TO


POSIX.1. System V has a __cuserid__ function which uses
the real user ID rather than the effective user ID. The
__cuserid__ function was included in the 1988 version of
POSIX, but removed from the 1990 version.
!!BUGS


Unfortunately, it is often rather easy to fool getlogin().
Sometimes it does not work at all, because some program
messed up the utmp file. Often, it gives only the first 8
characters of the login name. The user currently logged in
on the controlling tty of our program need not be the user
who started it. Avoid getlogin() for security-related
purposes.


Nobody knows precisely what cuserid() does - avoid it in
portable programs - avoid it altogether - use
getpwuid(geteuid()) instead, if that is what you meant. DO
NOT USE cuserid().
!!SEE ALSO


geteuid(2), getuid(2)
----

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Last edited on Tuesday, June 4, 2002 12:24:15 am by "perry"

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