Fix wrong argument of write. Fix return type of getdents. Fix procfs_getdents. Finish implementing the base version of the ps command.

libc/src/stdio.c

@@ -9,13 +9,14 @@
 #include "string.h"
 #include "stdbool.h"
 #include "sys/unistd.h"
+#include "strerror.h"
 
 void putchar(int character)
 {
     write(STDOUT_FILENO, &character, 1);
 }
 
-void puts(char *str)
+void puts(const char *str)
 {
     write(STDOUT_FILENO, str, strlen(str));
 }
@@ -206,3 +207,13 @@ char *fgets(char *buf, int n, int fd)
         return NULL;
     return (p);
 }
+
+void perror(const char *s)
+{
+    if (s) {
+        puts(s);
+        putchar(':');
+        putchar(' ');
+    }
+    puts(strerror(errno));
+}