#include	<sys/stat.h>#include	<dirent.h>#include	<limits.h>#include	<string.h>#include	<termios.h>#include	<unistd.h>#include	<stdlib.h>struct devdir {	struct devdir	*d_next;	char			*d_name;};static struct devdir	*head;static struct devdir	*tail;static char				pathname[_POSIX_PATH_MAX + 1];static voidadd(char *dirname){	struct devdir	*ddp;	int				len;	len = strlen(dirname);	/*	 * Skip ., .., and /dev/fd.	 */	if ((dirname[len-1] == '.') && (dirname[len-2] == '/' ||	  (dirname[len-2] == '.' && dirname[len-3] == '/')))		return;	if (strcmp(dirname, "/dev/fd") == 0)		return;	ddp = malloc(sizeof(struct devdir));	if (ddp == NULL)		return;	ddp->d_name = strdup(dirname);	if (ddp->d_name == NULL) {		free(ddp);		return;	}	ddp->d_next = NULL;	if (tail == NULL) {		head = ddp;		tail = ddp;	} else {		tail->d_next = ddp;		tail = ddp;	}}static voidcleanup(void){	struct devdir	*ddp, *nddp;	ddp = head;	while (ddp != NULL) {		nddp = ddp->d_next;		free(ddp->d_name);		free(ddp);		ddp = nddp;	}	head = NULL;	tail = NULL;}static char *searchdir(char *dirname, struct stat *fdstatp){	struct stat		devstat;	DIR				*dp;	int				devlen;	struct dirent	*dirp;	strcpy(pathname, dirname);	if ((dp = opendir(dirname)) == NULL)		return(NULL);	strcat(pathname, "/");	devlen = strlen(pathname);	while ((dirp = readdir(dp)) != NULL) {		strncpy(pathname + devlen, dirp->d_name,		  _POSIX_PATH_MAX - devlen);		/*		 * Skip aliases.		 */		if (strcmp(pathname, "/dev/stdin") == 0 ||		  strcmp(pathname, "/dev/stdout") == 0 ||		  strcmp(pathname, "/dev/stderr") == 0)			continue;		if (stat(pathname, &devstat) < 0)			continue;		if (S_ISDIR(devstat.st_mode)) {			add(pathname);			continue;		}		if (devstat.st_ino == fdstatp->st_ino &&		  devstat.st_dev == fdstatp->st_dev) {	/* found a match */			closedir(dp);			return(pathname);		}	}	closedir(dp);	return(NULL);}char *ttyname(int fd){	struct stat		fdstat;	struct devdir	*ddp;	char			*rval;	if (isatty(fd) == 0)		return(NULL);	if (fstat(fd, &fdstat) < 0)		return(NULL);	if (S_ISCHR(fdstat.st_mode) == 0)		return(NULL);	rval = searchdir("/dev", &fdstat);	if (rval == NULL) {		for (ddp = head; ddp != NULL; ddp = ddp->d_next)			if ((rval = searchdir(ddp->d_name, &fdstat)) != NULL)				break;	}	cleanup();	return(rval);}