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-rw-r--r--examples/loadables/mypid.c89
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
+};