POSIX: add tcgetsid()

Change-Id: If58141b4e56b7fe444460b6808e33abc5ea71f37
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3374
Reviewed-by: Axel Dörfler <[email protected]>

headers/posix/termios.h

@@ -187,6 +187,7 @@ struct termios {
 #define TIOCCBRK			(TCGETA + 21)	/* both are a frontend to TCSBRK */
 #define TIOCMBIS			(TCGETA + 22)	/* set bits in line state */
 #define TIOCMBIC			(TCGETA + 23)	/* clear bits in line state */
+#define	TIOCGSID			(TCGETA + 24)	/* get session leader process group ID */
 
 /* Event codes.  Returned from TCWAITEVENT */
 #define EV_RING			0x0001
@@ -233,6 +234,7 @@ extern int		tcsendbreak(int fd, int duration);
 extern int		tcdrain(int fd);
 extern int		tcflow(int fd, int action);
 extern int		tcflush(int fd, int queueSelector);
+extern pid_t	tcgetsid(int fd);
 
 #ifdef __cplusplus
 }

src/add-ons/kernel/drivers/tty/tty.cpp

@@ -1679,6 +1679,15 @@ tty_ioctl(tty_cookie* cookie, uint32 op, void* buffer, size_t length)
 			return B_OK;
 		}
 
+		// get session leader process group ID
+
+		case TIOCGSID:
+		{
+			TRACE(("tty: get session_id\n"));
+			return user_memcpy(buffer, &tty->settings->session_id,
+				sizeof(pid_t));
+		}
+
 		// get and set window size
 
 		case TIOCGWINSZ:

src/system/libroot/posix/termios.c

@@ -167,3 +167,16 @@ cfmakeraw(struct termios *termios)
 	termios->c_cflag &= ~(CSIZE | PARENB);
 	termios->c_cflag |= CS8;
 }
+
+
+pid_t
+tcgetsid(int fd)
+{
+	int sid;
+
+	if (ioctl(fd, TIOCGSID, &sid) == 0)
+		return sid;
+
+	return -1;
+}
+