ultrix man page for cuserid

cuserid(3s)															       cuserid(3s)

Name
       cuserid - get character login name of the user

Syntax
       #include <stdio.h>

       char *cuserid (s)
       char *s;

Description
       The  subroutine generates a character-string representation of the login name of the owner of the current process.  If s is a NULL pointer,
       this representation is generated in an internal static area, the address of which is returned.  Otherwise, s is	assumed  to  point  to	an
       array of at least characters; the representation is left in this array.	The constant is defined in the <stdio.h> header file.

Return Values
       If the login name cannot be found, returns a NULL pointer; if s is not a NULL pointer, a null character () will be placed at s[0].

       In POSIX mode, if s is not a NULL pointer, s is the return value.

Environment
       When  your  program  is compiled using the POSIX environment, returns the name associated with the effective userid of the calling process.
       When compiled in the BSD or System V environments, it returns the name associated with the login activity on the controlling  terminal,	if
       any.  Otherwise, it returns the same as in the POSIX environment.

See Also
       getlogin(3), getpwent(3)

																       cuserid(3s)