Remove the tcsetpgrp() code, as it did not work, since it turns out that zsh 5.8 was setting the terminal process group ID to that of itself when the last command in the pipeline was not a subshell - not to an invalid pgid or anything like that - so we cannot safely detect this or work around it.

src/pv/display.c

@@ -23,9 +23,6 @@
 #include <termios.h>
 #endif
 
-/* Use tcsetpgrp() workaround - see issue #100 and comments below. */
-/* #define USE_TCSETPGRP 1 */
-
 /*
  * We need sys/ioctl.h for ioctl() regardless of whether TIOCGWINSZ is
  * defined in termios.h, so we no longer use AC_HEADER_TIOCGWINSZ in
@@ -87,76 +84,12 @@ bool pv_in_foreground(void)
 		debug("true: %s (%d)", "our_process_group == tty_process_group", our_process_group);
 		return true;
 	}
-#if USE_TCSETPGRP
-	/*
-	 * If the terminal process group ID isn't our own process group ID,
-	 * then first check that the terminal process group ID actually
-	 * exists.
-	 */
 
-	if (0 == kill(-tty_process_group, 0)) {
-		/*
-		 * If it does exist, then we're not in the foreground, so
-		 * return false.
-		 */
-		debug("false: our_process_group=%d, tty_process_group=(%d and confirmed to exist)",
-		      our_process_group, tty_process_group);
-	} else if (errno == ESRCH) {
-		/*
-		 * If it doesn't exist (kill(0) gave ESRCH), then try
-		 * setting the terminal process group ID back to our process
-		 * group ID, to forcibly put ourselves into the foreground
-		 * (see issue #100), and try reading it back again.  If we
-		 * successfully set it to our process group ID then we're in
-		 * the foreground, so return true; otherwise we can't be
-		 * sure we're in the foreground, so return false.
-		 *
-		 * This is because the manual says the function tcgetpgrp()
-		 * will return the foreground process group ID of that
-		 * terminal if there is one, and some value larger than 1
-		 * that is not presently a process group ID otherwise.
-		 *
-		 * The assumption we're making is that tcgetpgrp() can
-		 * return a non-pgid value if there's no pgid for this
-		 * terminal right now, implying that maybe we can just set
-		 * it to our own.
-		 */
-		debug("-: our_process_group=%d, tty_process_group=(%d which returned ESRCH)",
-		      our_process_group, tty_process_group);
-		/*@-type@ *//* __pid_t vs pid_t, not significant */
-		if (0 == tcsetpgrp(STDERR_FILENO, our_process_group)) {
-			tty_process_group = tcgetpgrp(STDERR_FILENO);
-			/*@+type@ */
-			if (our_process_group == tty_process_group) {
-				debug
-				    ("true: our_process_group == tty_process_group (after tcsetpgrp to change it to %d)",
-				     our_process_group);
-				return true;
-			}
-			debug("false: our_process_group=%d, tty_process_group=(%d even after tcsetpgrp)",
-			      our_process_group, tty_process_group);
-		} else {
-			debug("false: our_process_group=%d, tty_process_group=(%d and tcsetpgrp returned \"%s\")",
-			      our_process_group, tty_process_group, strerror(errno));
-		}
-	} else {
-		/*
-		 * We can't determine whether the terminal process group ID
-		 * exists, all we know is it doesn't match our own, so
-		 * assume we're in the background, and return false.
-		 */
-		debug("false: our_process_group=%d, tty_process_group=(%d, kill returned \"%s\")",
-		      our_process_group, tty_process_group, strerror(errno));
-	}
-
-#else
 	/*
-	 * Simply assume we're in the background, if the terminal process
-	 * group ID doesn't match our own.
+	 * If the terminal process group ID doesn't match our own, assume
+	 * we're in the background.
 	 */
-	debug("false: our_process_group=%d, tty_process_group=%d, errno is %d",
-	      our_process_group, tty_process_group, (int) errno);
-#endif
+	debug("false: our_process_group=%d, tty_process_group=%d", our_process_group, tty_process_group);
 
 	return false;
 }