--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toys/other/sysctl.c	Thu May 15 05:34:08 2014 -0500
@@ -0,0 +1,152 @@
+/* sysctl.c - A utility to read and manipulate the sysctl parameters.
+ *
+ * Copyright 2014 Bilal Qureshi <bilal.jmi@gmail.com>
+ * Copyright 2014 Kyungwan Han <asura321@gmail.com>
+ *
+ * No Standard
+ 
+USE_SYSCTL(NEWTOY(sysctl, "^neNqwpaA[!ap][!aq][!aw][+aA]", TOYFLAG_USR|TOYFLAG_BIN))
+
+config SYSCTL
+  bool "sysctl"
+  default y
+  help
+    usage: sysctl [-aAeNnqw] [-p [FILE] | KEY[=VALUE]...]
+
+    Read/write system control data (under /proc/sys).
+
+    -a,A	Show all values
+    -e	Don't warn about unknown keys
+    -N	Don't print key values
+    -n	Don't print key names
+    -p [FILE]	Read values from FILE (default /etc/sysctl.conf)
+    -q	Don't show value after write
+    -w	Only write values (object to reading)
+*/
+#define FOR_sysctl
+#include "toys.h"
+
+// Null terminate at =, return value
+static char *split_key(char *key)
+{
+  char *value = strchr(key, '=');
+
+  if (value) *(value++)=0;
+
+  return value;
+}
+
+static void replace_char(char *str, char old, char new)
+{
+  for (; *str; str++) if (*str == old) *str = new;
+}
+
+static void key_error(char *key)
+{
+  if (errno == ENOENT) {
+    if (!(toys.optflags & FLAG_e)) error_msg("unknown key '%s'", key);
+  } else perror_msg("key '%s'", key);
+}
+
+static int write_key(char *path, char *key, char *value)
+{
+  int fd = open(path, O_WRONLY);;
+
+  if (fd < 0) {
+    key_error(key);
+
+    return 0;
+  }
+  xwrite(fd, value, strlen(value));
+  xclose(fd);
+
+  return 1;
+}
+
+// Display all keys under a path
+static int do_show_keys(struct dirtree *dt)
+{
+  char *path, *data, *key;
+
+  if (!dirtree_notdotdot(dt)) return 0; // Skip . and ..
+  if (S_ISDIR(dt->st.st_mode)) return DIRTREE_RECURSE;
+
+  path = dirtree_path(dt, 0);
+  data = readfile(path, 0, 0);
+  replace_char(key = path + 10, '/', '.'); // skip "/proc/sys/"
+  if (!data) key_error(key);
+  else {
+    // Print the parts that aren't switched off by flags.
+    if (!(toys.optflags & FLAG_n)) xprintf("%s", key);
+    if (!(toys.optflags & (FLAG_N|FLAG_n))) xprintf(" = ");
+    for (key = data+strlen(data); key > data && isspace(*--key); *key = 0);
+    if (!(toys.optflags & FLAG_N)) xprintf("%s", data);
+    if ((toys.optflags & (FLAG_N|FLAG_n)) != (FLAG_N|FLAG_n)) xputc('\n');
+  }
+
+  free(data);
+  free(path);
+
+  return 0;
+}
+
+// Read/write entries under a key. Accepts "key=value" in key if !value
+static void process_key(char *key, char *value)
+{
+  char *path;
+
+  if (!value) value = split_key(key);
+  if ((toys.optflags & FLAG_w) && !value) {
+    error_msg("'%s' not key=value");
+
+    return;
+  }
+
+  path = xmprintf("/proc/sys/%s", key);
+  replace_char(path, '.', '/');
+  // Note: failure to assign to a non-leaf node suppresses the display.
+  if (!(value && (!write_key(path, key, value) || (toys.optflags & FLAG_q)))) {
+    if (!access(path, R_OK)) dirtree_read(path, do_show_keys);
+    else key_error(key);
+  }
+  free(path);
+}
+
+void sysctl_main()
+{
+  char **args = 0;
+
+  // Display all keys
+  if (toys.optflags & FLAG_a) dirtree_read("/proc/sys", do_show_keys);
+
+  // read file
+  else if (toys.optflags & FLAG_p) {
+    FILE *fp = xfopen(*toys.optargs ? *toys.optargs : "/etc/sysctl.conf", "r");
+    size_t len;
+
+    for (;;) {
+      char *line = 0, *key, *val;
+
+      if (-1 == (len = getline(&line, &len, fp))) break;
+      key = line;
+      while (isspace(*key)) key++;
+      if (*key == '#' || *key == ';' || !*key) continue;
+      while (len && isspace(line[len-1])) line[--len] = 0;
+      if (!(val = split_key(line))) {
+        error_msg("'%s' not key=value", line);
+        continue;
+      }
+
+      // Trim whitespace around =
+      len = (val-line)-1;
+      while (len && isspace(line[len-1])) line[--len] = 0;
+      while (isspace(*val)) val++;;
+
+      process_key(key, val);
+      free(line);
+    }
+    fclose(fp);
+
+  // Loop through arguments, displaying or assigning as appropriate
+  } else for (args = toys.optargs; *args; args++) process_key(*args, 0);
+}