usr/src/libc/gen/ttyname.c

/*
 * ttyname(f): return "/dev/ttyXX" which the the name of the
 * tty belonging to file f.
 *  NULL if it is not a tty
 */

#define NULL    0
#include <sys/types.h>
#include <sys/dir.h>
#include <sys/stat.h>

static  char    dev[]   = "/dev/";
char    *strcpy();
char    *strcat();

char *
ttyname(f)
{
        struct stat fsb;
        struct stat tsb;
        struct direct db;
        static char rbuf[32];
        register df;

        if (isatty(f)==0)
                return(NULL);
        if (fstat(f, &fsb) < 0)
                return(NULL);
        if ((fsb.st_mode&S_IFMT) != S_IFCHR)
                return(NULL);
        if ((df = open(dev, 0)) < 0)
                return(NULL);
        while (read(df, (char *)&db, sizeof(db)) == sizeof(db)) {
                if (db.d_ino == 0)
                        continue;
                if (db.d_ino != fsb.st_ino)
                        continue;
                strcpy(rbuf, dev);
                strcat(rbuf, db.d_name);
                if (stat(rbuf, &tsb) < 0)
                        continue;
                if (tsb.st_dev==fsb.st_dev && tsb.st_ino==fsb.st_ino) {
                        close(df);
                        return(rbuf);
                }
        }
        close(df);
        return(NULL);
}