1 files changed, 89 insertions, 0 deletions
diff --git a/examples/loadables/mypid.c b/examples/loadables/mypid.c
new file mode 100644
index 0000000..fc1b267
--- /dev/null
+++ b/examples/loadables/mypid.c
@@ -0,0 +1,89 @@
+/* This module should be dynamically loaded with enable -f
+ * which would create a new builtin named mypid. You'll need
+ * the source code for GNU bash to recompile this module.
+ *
+ * Then, from within bash, enable -f ./mypid enable_mypid, where ./mypid
+ * is the binary obtained from running make. Hereafter, `${MYPID}'
+ * is a shell builtin variable.
+ *
+ * This defines an unload hook function that is called when the builtin is
+ * deleted with enable -d that will unbind the MYPID variable so future
+ * references to it do not attempt to access memory that is no longer part
+ * of this process's address space.
+ */
+#include <config.h>
+
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+
+#include "builtins.h"
+#include "shell.h"
+
+#define INIT_DYNAMIC_VAR(var, val, gfunc, afunc) \
+  do \
+    { SHELL_VAR *v = bind_variable (var, (val), 0); \
+      if (v) \
+	{ \
+	  v->dynamic_value = gfunc; \
+	  v->assign_func = afunc; \
+	} \
+    } \
+  while (0)
+
+static SHELL_VAR *
+assign_mypid (
+     SHELL_VAR *self,
+     char *value,
+     arrayind_t unused,
+     char *key )
+{
+  return (self);
+}
+
+static SHELL_VAR *
+get_mypid (SHELL_VAR *var)
+{
+  int rv;
+  char *p;
+
+  rv = getpid();
+  p = itos (rv);
+
+  FREE (value_cell (var));
+
+  VSETATTR (var, att_integer);
+  var_setvalue (var, p);
+  return (var);
+}
+
+int
+enable_mypid_builtin(WORD_LIST *list)
+{
+  INIT_DYNAMIC_VAR ("MYPID", (char *)NULL, get_mypid, assign_mypid);
+
+  return 0;
+}
+
+void
+enable_mypid_builtin_unload (char *s)
+{
+  unbind_variable ("MYPID");
+}
+
+char const *enable_mypid_doc[] = {
+  "Enable $MYPID.",
+  "",
+  "Enables use of the ${MYPID} dynamic variable.  ",
+  "It will yield the current pid of a subshell.",
+  (char *)0
+};
+
+struct builtin enable_mypid_struct = {
+  "enable_mypid",
+  enable_mypid_builtin,
+  BUILTIN_ENABLED,
+  (char**)(void*)enable_mypid_doc,
+  "enable_mypid N",
+  0
+};