usr/src/lib/libc/gen/getlogin.c

/*      @(#)getlogin.c  4.1 (Berkeley) %G%      */
#include <utmp.h>

static  char    UTMP[]  = "/etc/utmp";
static  struct  utmp ubuf;

char *
getlogin()
{
        register me, uf;
        register char *cp;

        if( !(me = ttyslot()) )
                return(0);
        if( (uf = open( UTMP, 0 )) < 0 )
                return(0);
        lseek( uf, (long)(me*sizeof(ubuf)), 0 );
        if (read(uf, (char *)&ubuf, sizeof(ubuf)) != sizeof(ubuf))
                return(0);
        close(uf);
        ubuf.ut_name[sizeof (ubuf.ut_name)] = ' ';
        for (cp=ubuf.ut_name; *cp++!=' ';)
                ;
        *--cp = '\0';
        return( ubuf.ut_name );
}