userland: add "mkfifo" command

userland/Makefile

@@ -24,6 +24,7 @@ BIN_TARGET_NAMES := \
 	ls \
 	mandelbrot \
 	mkdir \
+	mkfifo \
 	mount \
 	mouse-cursor \
 	moused \
@@ -63,6 +64,7 @@ LIB_OBJS := \
 	lib/stdio.o \
 	lib/stdlib.o \
 	lib/string.o \
+	lib/sys/stat.o \
 	lib/syscall.o \
 	lib/time.o \
 	lib/unistd.o

userland/lib/sys/stat.c

@@ -0,0 +1,6 @@
+#include "stat.h"
+#include <unistd.h>
+
+int mkfifo(const char* pathname, mode_t mode) {
+    return mknod(pathname, mode | S_IFIFO, 0);
+}

userland/lib/sys/stat.h

@@ -4,3 +4,4 @@
 
 int stat(const char* pathname, struct stat* buf);
 int mkdir(const char* pathname, mode_t mode);
+int mkfifo(const char* pathname, mode_t mode);

userland/mkfifo.c

@@ -0,0 +1,16 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+int main(int argc, char* const argv[]) {
+    if (argc != 2) {
+        dprintf(STDERR_FILENO, "Usage: mkfifo NAME\n");
+        return EXIT_FAILURE;
+    }
+    if (mkfifo(argv[1], 0) < 0) {
+        perror("mkfifo");
+        return EXIT_FAILURE;
+    }
+    return EXIT_SUCCESS;
+}