Watch implementation changes

watch/watch.c

@@ -1,15 +1,17 @@
-/* 
+/*
  * watch.c - Keep an eye on a command output
+ *
  */
 /*
- * Copyright (C) 2023: Luiz Antônio Rangel (takusuman)
+ * Copyright (C) 2023, 2024: Luiz Antônio Rangel (takusuman)
+ * 			     Arthur Bacci	 (arthurbacci)
  *
  * SPDX-Licence-Identifier: Zlib
  *
  * Support for calling commands with arguments without having to escape them
  * with double-dash thoroughly based of IIJ's iwatch(1).
  * As per the copyright header of IIJ's iwatch.c:
- * Copyright (c) 2000, 2001 Internet Initiative Japan Inc. 
+ * Copyright (c) 2000, 2001 Internet Initiative Japan Inc.
  *
  * SPDX-Licence-Identifier: BSD-2-Clause
  */
@@ -31,120 +33,237 @@ static char *progname;
 int main(int argc, char *argv[]);
 void usage(void);
 
-struct Flag {
-	int Beep_on_error, No_title;
-}; static struct Flag flag;
-
 int main(int argc, char *argv[]) {
 	progname = argv[0];
-	// Initialize every integer, to avoid warnings when compiling
-	// with -Wconditional-uninitialized.
-	// Default interval of 2 seconds, as other major implementations
-	// usually do.
-	int option = 0,
-	    interval = 2,
-	    c = 0,
-	    ec = 0,
-	    term_x = 0,
-	    term_y = 0;
+	int option = 0;
+	int fBeep_on_error = 0,
+	    fNo_title = 0,
+	    c = 0, ec = 0,
+	    term_x = 0;
 	char **commandv;
 	pid_t exec_pid;
+	struct timespec interval = {0};
 
-	// Variables for the information header.
-	// Defining nodename from now, since it shouldn't change while we're
-	// watching the command.
+	/*
+	 * Default interval of 2 seconds, as other major
+	 * implementations usually do.
+	 */
+	interval.tv_sec = 2;
+
+	/*
+	 * Variables for the information header.
+	 * Defining nodename from now, since it shouldn't change
+	 * while we're watching the command.
+	 */
 	time_t now;
+	struct tm *timeinfo;
 	struct utsname u;
-	if ( uname(&u) == -1 ) {
+	if (uname(&u) == -1) {
 		prerror(errno);
 		exit(-1);
 	}
 
-	while ( (option = getopt(argc, argv, "n:hbt")) != -1 ) {
-			switch (option) {
-				case 'n':
-					interval = atoi(optarg);
-					break;
-				case 'b':
-					flag.Beep_on_error = 1;
-					break;
-				case 't':
-					flag.No_title = 1;
+	while ((option = getopt(argc, argv, "n:hbt")) != -1) {
+		switch (option) {
+		case 'n':
+			if (!optarg) {
+			       	break;
+			}
+			char arg[128];
+			char *afterpoint = NULL;
+			strncpy(arg, optarg, 128);
+			arg[127] = '\0';
+
+			size_t point = 0;
+			for (; arg[point]; point++) {
+				if (arg[point] == '.' || arg[point] == ',') {
+					arg[point] = '\0';
+					afterpoint = &arg[point + 1];
 					break;
-				case 'h':
-				default:
-					usage();
+				}
 			}
+
+			if (strlen(arg) == 0) {
+			       	interval.tv_sec = 0;
+			} else {
+			       	interval.tv_sec = atoi(arg);
+			}
+
+			size_t afterpointlen = afterpoint ? strlen(afterpoint) : 0;
+			if (afterpointlen > 0) {
+				long integer = atoi(afterpoint);
+
+				if (afterpointlen > 9) {
+					afterpoint[9] = '\0';
+					afterpointlen = 9;
+				}
+
+				for (size_t i = 0; i < 9 - afterpointlen; i++)
+					integer *= 10;
+
+				interval.tv_nsec = integer;
+			}
+
+			if (interval.tv_sec == 0 && interval.tv_nsec < 100000000) {
+				interval.tv_nsec = 100000000;
+			}
+
+			break;
+		case 'b':
+			fBeep_on_error = 1;
+			break;
+		case 't':
+			fNo_title = 1;
+			break;
+		case 'h':
+		default:
+			usage();
+		}
 	}
+
+	/* FIXME: Not a good practice. */
 	argc -= optind;
 	argv += optind;
 
-	// Missing operand
-	if ( argc < 1 ){
+	/* Missing operand. */
+	if (argc < 1) {
 		usage();
 	}
 
-	// Now we just have to copy the "rest" of argv[] to a new character
-	// array allocating some space in memory with calloc(3) and then
-	// copying using a for loop.
-
-	if ( (commandv = calloc((unsigned long)(argc + 1), sizeof(char *))) == NULL ) {
-		prerror(errno);
+	/*
+	 * Now we just have to copy the "rest" of argv[] to a new character
+	 * array allocating some space in memory with calloc(3) and then
+	 * copying using a for loop.
+	 */
+	if ((commandv = calloc((unsigned long)(argc + 1), sizeof(char *))) == NULL) {
+		/* Should I use prerror? */
+		perror("couldn't callocate");
 		exit(-1);
 	}
 
-	for ( c = 0; c < argc; c++ ) {
+	for (c = 0; c < argc; c++) {
 		commandv[c] = argv[c];
 	}
 
-	// Initialize curses terminal with colours to be used.
-	// Get terminal size too, we're going to need it.
+	/*
+	 * Initialize curses terminal with colours to be used.
+	 * Get terminal size too, we're going to need it.
+	 */
 	newterm(getenv("TERM"), stdout, stdin);
 	start_color();
 	init_pair(1, COLOR_BLACK, COLOR_WHITE);
-	getmaxyx(stdscr, term_y, term_x);
 
+	/*
+	 * Declaring the left side of the information header, which contains
+	 * "Every χ second(s): ...", outside the loop because it's immutable
+	 * after we got the program we're going to run and the amount of time.
+	 */
+	static int left_len = 0;
+	static char left[256];
+	if (!fNo_title) {
+		/*
+		 * FIXME: When one uses "-n 0.1", it actually prints 
+		 * "0.100000000" instead of 0.1 or even 0.10.
+		 */
+		left_len = snprintf(
+			left, 256, "Every %d.%d second(s): %s",
+			(int)interval.tv_sec, (int)interval.tv_nsec,
+			argv[0]
+		);
+	}
+
 	for (;;) {
-		// Get current time to be passed as a string with ctime(3).
+		/* Clear terminal for the next cycle. */
+		clear();
+
+		/* Get the terminal maximum x-axis size. */
+		term_x = getmaxx(stdscr);
+
+		/* Get current time to be passed as a string with ctime(3). */
 		time(&now);
-		if ( ! flag.No_title ){
+		timeinfo = localtime(&now);
+
+		if (!fNo_title) {
+			int right_len = 0; /* "left_len = 0" declared above. */
+			char right[256], time[256]; /* "left[256]" declared above. */
+
 			attron(COLOR_PAIR(1) | A_BOLD);
-			// Use a factor of terminal width (term_x) divided by 5,
-			// since it seems to work the best to keep the header at
-			// a "confortable" size.
-			printw("Every %d second(s): %-*s %s: %s\n",
-				interval, (term_x/5), argv[0], u.nodename, ctime(&now));
+
+			/*
+			 * This is done because ctime returns
+			 * a string with '\n'.
+			 */
+			strftime(time, 256, "%c", timeinfo);
+
+			right_len = snprintf(
+				right, 256, "%s: %s",
+				u.nodename, time
+			);
+
+			/*
+			 * I think that a case involving left_len and right_len,
+			 * which contain the "Every (int).(int) second(s): (string)"
+			 * and "hostname: date", respectively, is improbable, so
+			 * this is just a pure formality in case of one's
+			 * C library implementation having a faulty snprintf().
+			 */
+			if (left_len <= 0 || right_len <= 0) {
+				perror("please try to execute it without the information header.\n");
+				exit(255);
+			}
+
+			if (left_len <= term_x && right_len <= term_x) {
+				/*
+				 * If the sum of the text on left and right
+				 * sections of the bar is larger than the
+				 * terminal x axis, it shall be justified.
+				 * Else, keep it as normal.
+				 */
+				if (left_len + right_len >= term_x) {
+					printw("%-*s", term_x, left);
+					printw("%*s",  term_x, right);
+				} else {
+					printw("%s%*s", left, (term_x - left_len), right);
+				}
+				printw("\n");
+			}
+
 			attroff(COLOR_PAIR(1) | A_BOLD);
 		}
 
-		// Not using endwin(3x), since it breaks with multiline
-		// also-curses programs, such as ls(1) with the "-l" option.
+
+		/*
+		 * Not using endwin(3x), since it breaks with multiline
+		 * also-curses programs, such as ls(1) with the "-l" option.
+		 */
 		reset_shell_mode();
 		refresh();
 
-		if ( (exec_pid = fork()) == 0 ) {
-			if ( (execvp(commandv[0], commandv)) == -1 ) {
+		if ((exec_pid = fork()) == 0) {
+			if ((execvp(commandv[0], commandv)) == -1) {
 				prerror(errno);
 				exit(-1);
 			}
 		}
 		waitpid(exec_pid, &ec, 0);
 
-		// execvp'd command hasn't exit with success and we have
-		// flag.Beep_on_error activated.
-		if ( ec != 0 && flag.Beep_on_error ) {
+		/*
+		 * execvp'd command hasn't exit with success and we have
+		 * fBeep_on_error activated.
+		 */
+		if (ec != 0 && fBeep_on_error) {
 			beep();
 		}
 
-		sleep( (uint)(interval) );
-
-		// Clear terminal for the next cycle.
-		clear();
+		nanosleep(&interval, NULL);
 	}
 }
 
 void usage(void) {
-	pfmt(stderr, MM_NOSTD,
-		"usage: %s [-n seconds] [-bt] command [args...]\n", progname);
+	pfmt(
+		stderr, MM_NOSTD,
+		"usage: %s [-n seconds] [-bt] command [args...]\n",
+		progname
+	);
 	exit(1);
 }