examples/loadables/mypid.c

   1 /* This module should be dynamically loaded with enable -f
   2  * which would create a new builtin named mypid. You'll need
   3  * the source code for GNU bash to recompile this module.
   4  *
   5  * Then, from within bash, enable -f ./mypid enable_mypid, where ./mypid
   6  * is the binary obtained from running make. Hereafter, `${MYPID}'
   7  * is a shell builtin variable.
   8  */
   9
  10 #include <stdio.h>
  11 #include <errno.h>
  12 #include <string.h>
  13
  14 #include "builtins.h"
  15 #include "shell.h"
  16
  17 #define INIT_DYNAMIC_VAR(var, val, gfunc, afunc) \
  18   do \
  19     { SHELL_VAR *v = bind_variable (var, (val), 0); \
  20       v->dynamic_value = gfunc; \
  21       v->assign_func = afunc; \
  22     } \
  23   while (0)
  24
  25 static SHELL_VAR *
  26 assign_mypid (
  27      SHELL_VAR *self,
  28      char *value,
  29      arrayind_t unused,
  30      char *key )
  31 {
  32   return (self);
  33 }
  34
  35 static SHELL_VAR *
  36 get_mypid (SHELL_VAR *var)
  37 {
  38   int rv;
  39   char *p;
  40
  41   rv = getpid();
  42   p = itos (rv);
  43
  44   FREE (value_cell (var));
  45
  46   VSETATTR (var, att_integer);
  47   var_setvalue (var, p);
  48   return (var);
  49 }
  50
  51 int
  52 enable_mypid_builtin(WORD_LIST *list)
  53 {
  54   INIT_DYNAMIC_VAR ("MYPID", (char *)NULL, get_mypid, assign_mypid);
  55
  56   return 0;
  57 }
  58
  59 char const *enable_mypid_doc[] = {
  60   "Enable $MYPID.",
  61   "",
  62   "Enables use of the ${MYPID} dynamic variable.  ",
  63   "It will yield the current pid of a subshell.",
  64   (char *)0
  65 };
  66
  67 struct builtin enable_mypid_struct = {
  68   "enable_mypid",
  69   enable_mypid_builtin,
  70   BUILTIN_ENABLED,
  71   (char**)(void*)enable_mypid_doc,
  72   "enable_mypid N",
  73   0
  74 };