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.\"     from: @(#)ctermid.3	5.2 (Berkeley) 4/19/91
.\"
.Dd $Mdocdate: May 31 2007 $
.Dt CUSERID 3
.Os
.Sh NAME
.Nm cuserid
.Nd get user name
.Sh SYNOPSIS
.Fd #include <stdio.h>
.Ft char *
.Fn cuserid "char *buf"
.Sh DESCRIPTION
.Bf -symbolic
This interface is available from the compatibility library, libcompat.
.Ef
.Pp
The
.Fn cuserid
function returns a character string representation of the user name
associated with the effective user ID of the calling process.
.Pp
If
.Fa buf
is not the
.Dv NULL
pointer, the user name is copied into the memory referenced by
.Fa buf .
The argument
.Fa buf
is assumed to point to an array at least
.Dv L_cuserid
(as defined in the include
file
.Aq Pa stdio.h )
bytes long.
Otherwise, the user name is copied to a static buffer.
.Sh RETURN VALUES
If
.Fa buf
is not the
.Dv NULL
pointer,
.Fa buf
is returned;
otherwise the address of the static buffer is returned.
.Pp
If the user name could not be determined, if
.Fa buf
is not the
.Dv NULL
pointer, the null character
.Sq \e0
will be stored at
.Fa *buf ;
otherwise
the
.Dv NULL
pointer is returned.
.Sh SEE ALSO
.Xr getlogin 2 ,
.Xr getpwent 3
.Sh STANDARDS
The
.Fn cuserid
function conforms to
.St -p1003.1-88 .
.Sh BUGS
Due to irreconcilable differences in historic implementations,
.Fn cuserid
was removed from the
.St -p1003.1-90
standard.
This implementation exists purely for compatibility with existing programs.
New programs should use one of the following three alternatives to
obtain the user name:
.Pp
.Bl -enum -offset indent -compact
.It
.Fn getlogin
to return the user's login name.
.It
.Nm getpwuid Ns Pq Fn geteuid
to return the user name associated with the calling process' effective user ID.
.It
.Nm getpwuid Ns Pq Fn getuid
to return the user name associated with the calling process' real user ID.
.El
.Pp
The
.Fn cuserid
function uses
.Fn getpwuid ;
thus the results of a user's call to
.Fn getpwent ,
.Fn getpwnam
or
.Fn getpwuid
will be overwritten by subsequent calls to
.Fn cuserid .