tweaks: use the standard symbols for the three standard file descriptors

Also, take into account (as elsewhere) that dup2() could fail,
and harmonize their error checks.

src/definitions.h

@@ -135,8 +135,6 @@
 #define BAD_COLOR  -2
 #endif
 
-#define STANDARD_INPUT  0
-
 /* Enumeration types. */
 typedef enum {
 	NIX_FILE, DOS_FILE, MAC_FILE

src/files.c

@@ -722,7 +722,7 @@ void read_file(FILE *f, int fd, const char *filename, bool undoable)
 
 	/* When reading from stdin, restore the terminal and reenter curses mode. */
 	if (isendwin()) {
-		if (!isatty(STANDARD_INPUT))
+		if (!isatty(STDIN_FILENO))
 			reconnect_and_store_state();
 		terminal_init();
 		doupdate();
@@ -966,13 +966,16 @@ bool execute_command(const char *command)
 		close(from_fd[0]);
 
 		/* Connect the write end of the output pipe to the process' output streams. */
-		dup2(from_fd[1], fileno(stdout));
+		if (dup2(from_fd[1], STDOUT_FILENO) < 0)
-		dup2(from_fd[1], fileno(stderr));
+			exit(3);
+		if (dup2(from_fd[1], STDERR_FILENO) < 0)
+			exit(4);
 
 		/* If the parent sends text, connect the read end of the
 		 * feeding pipe to the child's input stream. */
 		if (should_pipe) {
-			dup2(to_fd[0], fileno(stdin));
+			if (dup2(to_fd[0], STDIN_FILENO) < 0)
+				exit(5);
 			close(to_fd[1]);
 		}
 
@@ -980,7 +983,7 @@ bool execute_command(const char *command)
 		execl(theshell, tail(theshell), "-c", should_pipe ? &command[1] : command, NULL);
 
 		/* If the exec call returns, there was an error. */
-		exit(1);
+		exit(6);
 	}
 
 	/* Parent: close the unused write end of the pipe. */

src/nano.c

@@ -225,7 +225,7 @@ void restore_terminal(void)
 	printf("\x1B[?2004l");
 	fflush(stdout);
 #endif
-	tcsetattr(0, TCSANOW, &original_state);
+	tcsetattr(STDIN_FILENO, TCSANOW, &original_state);
 }
 
 /* Exit normally: restore terminal state and report any startup errors. */
@@ -813,15 +813,14 @@ void reconnect_and_store_state(void)
 {
 	int thetty = open("/dev/tty", O_RDONLY);
 
-	if (thetty < 1)
+	if (thetty < 0 || dup2(thetty, STDIN_FILENO) < 0)
 		die(_("Could not reconnect stdin to keyboard\n"));
 
-	dup2(thetty, STANDARD_INPUT);
 	close(thetty);
 
 	/* If input was not cut short, store the current state of the terminal. */
 	if (!control_C_was_pressed)
-		tcgetattr(0, &original_state);
+		tcgetattr(STDIN_FILENO, &original_state);
 }
 
 /* Read whatever comes from standard input into a new buffer. */
@@ -832,7 +831,7 @@ bool scoop_stdin(void)
 	restore_terminal();
 
 	/* When input comes from a terminal, show a helpful message. */
-	if (isatty(STANDARD_INPUT))
+	if (isatty(STDIN_FILENO))
 		fprintf(stderr, _("Reading data from keyboard; "
 							"type ^D or ^D^D to finish.\n"));
 
@@ -1801,16 +1800,16 @@ int main(int argc, char **argv)
 	struct vt_stat dummy;
 
 	/* Check whether we're running on a Linux console. */
-	on_a_vt = (ioctl(1, VT_GETSTATE, &dummy) == 0);
+	on_a_vt = (ioctl(STDOUT_FILENO, VT_GETSTATE, &dummy) == 0);
 #endif
 
 	/* Back up the terminal settings so that they can be restored. */
-	tcgetattr(0, &original_state);
+	tcgetattr(STDIN_FILENO, &original_state);
 
 	/* Get the state of standard input and ensure it uses blocking mode. */
-	stdin_flags = fcntl(0, F_GETFL, 0);
+	stdin_flags = fcntl(STDIN_FILENO, F_GETFL, 0);
 	if (stdin_flags != -1)
-		fcntl(0, F_SETFL, stdin_flags & ~O_NONBLOCK);
+		fcntl(STDIN_FILENO, F_SETFL, stdin_flags & ~O_NONBLOCK);
 
 #ifdef ENABLE_UTF8
 	/* If setting the locale is successful and it uses UTF-8, we need

src/text.c

@@ -2340,11 +2340,11 @@ void do_int_speller(const char *tempfile_name)
 			exit(6);
 
 		/* Connect standard input to the temporary file. */
-		if (dup2(tempfile_fd, STDIN_FILENO) != STDIN_FILENO)
+		if (dup2(tempfile_fd, STDIN_FILENO) < 0)
 			exit(7);
 
 		/* Connect standard output to the write end of the first pipe. */
-		if (dup2(spell_fd[1], STDOUT_FILENO) != STDOUT_FILENO)
+		if (dup2(spell_fd[1], STDOUT_FILENO) < 0)
 			exit(8);
 
 		close(tempfile_fd);
@@ -2365,11 +2365,11 @@ void do_int_speller(const char *tempfile_name)
 	/* Fork a process to run sort in. */
 	if ((pid_sort = fork()) == 0) {
 		/* Connect standard input to the read end of the first pipe. */
-		if (dup2(spell_fd[0], STDIN_FILENO) != STDIN_FILENO)
+		if (dup2(spell_fd[0], STDIN_FILENO) < 0)
 			exit(7);
 
 		/* Connect standard output to the write end of the second pipe. */
-		if (dup2(sort_fd[1], STDOUT_FILENO) != STDOUT_FILENO)
+		if (dup2(sort_fd[1], STDOUT_FILENO) < 0)
 			exit(8);
 
 		close(spell_fd[0]);
@@ -2387,10 +2387,10 @@ void do_int_speller(const char *tempfile_name)
 
 	/* Fork a process to run uniq in. */
 	if ((pid_uniq = fork()) == 0) {
-		if (dup2(sort_fd[0], STDIN_FILENO) != STDIN_FILENO)
+		if (dup2(sort_fd[0], STDIN_FILENO) < 0)
 			exit(7);
 
-		if (dup2(uniq_fd[1], STDOUT_FILENO) != STDOUT_FILENO)
+		if (dup2(uniq_fd[1], STDOUT_FILENO) < 0)
 			exit(8);
 
 		close(sort_fd[0]);
@@ -2607,9 +2607,9 @@ void do_linter(void)
 	/* Fork a process to run the linter in. */
 	if ((pid_lint = fork()) == 0) {
 		/* Redirect standard output and standard error into the pipe. */
-		if (dup2(lint_fd[1], STDOUT_FILENO) != STDOUT_FILENO)
+		if (dup2(lint_fd[1], STDOUT_FILENO) < 0)
 			exit(7);
-		if (dup2(lint_fd[1], STDERR_FILENO) != STDERR_FILENO)
+		if (dup2(lint_fd[1], STDERR_FILENO) < 0)
 			exit(8);
 
 		close(lint_fd[0]);