mdirs: add -0 to separate folders by NUL characters

Idea by Mario Domgoergen <mdom@taz.de>.

Closes #159.

man/mdirs.1

@@ -6,6 +6,7 @@
 .Nd list maildir folders, recursively
 .Sh SYNOPSIS
 .Nm
+.Op Fl 0
 .Ar dirs\ ...
 .Sh DESCRIPTION
 .Nm
@@ -27,7 +28,11 @@ By the maildir++ convention, nested maildir folder
 names must begin with
 .Sq Li \&. .
 .Pp
-There are currently no options.
+The options are as follows:
+.Bl -tag -width Ds
+.It Fl 0
+Print folders separated by a NUL character.
+.El
 .Sh EXIT STATUS
 .Ex -std
 .Sh SEE ALSO

mdirs.c

@@ -9,12 +9,14 @@
 
 #include "blaze822.h"
 
+static char sep = '\n';
+
 void
 pwd()
 {
 	char cwd[PATH_MAX];
 	if (getcwd(cwd, sizeof cwd))
-		puts(cwd);
+		printf("%s%c", cwd, sep);
 }
 
 void
@@ -72,11 +74,12 @@ int
 main(int argc, char *argv[])
 {
 	int c, i;
-	while ((c = getopt(argc, argv, "")) != -1)
+	while ((c = getopt(argc, argv, "0")) != -1)
 		switch (c) {
+		case '0': sep = '\0'; break;
 		default:
 usage:
-			fprintf(stderr, "Usage: mdirs dirs...\n");
+			fprintf(stderr, "Usage: mdirs [-0] dirs...\n");
 			exit(1);
 		}