Hi,
As far as I am able to tell, there is no well-known way to ascertain the
current pid of a subshell. You can write programs that return their
parent's pid, but that is pretty hacky. So, I dug through some sketchy
docs and examples about rolling your own built in BASH commands and
came up with something that almost works. Sigh. I'm sure it is pretty
close. Anybody with a few minutes to give me a hint? :) Thanks - Bruce
/* 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.
*/
#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); \
v->dynamic_value = gfunc; \
v->assign_func = afunc; \
} \
while (0)
static SHELL_VAR *
assign_mypid (
SHELL_VAR *self,
char *value,
arrayind_t unused )
{
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;
}
char const *enable_mypid_doc[] = {
"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
};
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