Make ancestor directories before writing htoprc

... and don't create config directories when reading the htop config.

The new subroutine for creating directories can also work with custom
paths specified in HTOPRC environment variable.

Signed-off-by: Kang-Che Sung <explorer09@gmail.com>

Author: Explorer09

Settings.c

@@ -9,6 +9,7 @@ in the source distribution for its full text.
 
 #include "Settings.h"
 
+#include <assert.h>
 #include <ctype.h>
 #include <errno.h>
 #include <fcntl.h>
@@ -563,6 +564,51 @@ static bool Settings_read(Settings* this, const char* fileName, const Machine* h
    return didReadAny;
 }
 
+static int makeAncestorDirectories(char* filePath, size_t len) {
+   assert(len == strlen(filePath));
+
+   // The caller is expected to set the umask before calling this function.
+   // In particular, if the umask contains S_IWUSR or S_IXUSR bit then the
+   // making of subdirectories within the ancestor can fail.
+
+   int ret = 0;
+   int savedErr = errno;
+
+   char *p = filePath + len;
+   for (; p > filePath; p--) {
+      if (*p != '/')
+         continue;
+
+      *p = '\0';
+      bool ok = !mkdir(filePath, S_IRWXU);
+      *p = '/';
+      if (ok)
+         break;
+
+      if (errno != ENOENT)
+         return -errno;
+
+      ret = -errno;
+   }
+   if (p <= filePath)
+      return ret;
+
+   errno = savedErr;
+
+   while (++p < filePath + len) {
+      assert(*p);
+      if (*p != '/')
+         continue;
+
+      *p = '\0';
+      bool ok = !mkdir(filePath, S_IRWXU);
+      *p = '/';
+      if (!ok)
+         return -errno;
+   }
+   return 0;
+}
+
 typedef ATTR_FORMAT(printf, 2, 3) int (*OutputFunc)(FILE*, const char*,...);
 
 static void writeFields(OutputFunc of, FILE* fp,
@@ -649,9 +695,15 @@ int Settings_write(const Settings* this, bool onCrash) {
    } else if (!this->writeConfig) {
       return 0;
    } else {
-      /* create tempfile with mode 0600 */
-      mode_t cur_umask = umask(S_IXUSR | S_IRWXG | S_IRWXO);
-      xAsprintf(&tmpFilename, "%s.tmp.XXXXXX", this->filename);
+      // Prepare temp filename
+      size_t nameLen = (size_t)xAsprintf(&tmpFilename, "%s.tmp.XXXXXX", this->filename);
+
+      // Create ancestor directories with mode 0700
+      mode_t cur_umask = umask(S_IRWXG | S_IRWXO);
+      makeAncestorDirectories(tmpFilename, nameLen);
+
+      // Create temp file with mode 0600
+      umask(S_IXUSR | S_IRWXG | S_IRWXO);
       int fdtmp = mkstemp(tmpFilename);
       umask(cur_umask);
       if (fdtmp == -1) {
@@ -851,8 +903,6 @@ Settings* Settings_new(const Machine* host, Hashtable* dynamicMeters, Hashtable*
          configDir = String_cat(home, CONFIGDIR);
          htopDir = String_cat(home, CONFIGDIR "/htop");
       }
-      (void) mkdir(configDir, 0700);
-      (void) mkdir(htopDir, 0700);
       free(htopDir);
       free(configDir);