#include <tcl.h>
#include <stdlib.h>
#include <string.h>

int main(int argc, char **argv)
{
    if (argc != 4) {
        fprintf (stderr, "Usage: %s haystack needle str\n", argv[0]);
        return (1);
    }

    char *haystack = argv[1];
    char *needle   = argv[2];
    char *str      = argv[3];

    char cmdlen = strlen("regsub -all {") + strlen(needle) + strlen("} {") +
        strlen(haystack) + strlen("} {") + strlen(str) + strlen("}") + 1;

    char *expr = malloc (cmdlen);
    snprintf (expr, cmdlen, "regsub -all {%s} {%s} {%s}", needle, haystack, str);

    Tcl_Interp *interp;
    interp = Tcl_CreateInterp ();
    Tcl_Eval (interp, expr);
    printf ("%s\n", Tcl_GetStringResult (interp));
    Tcl_DeleteInterp (interp);

    free (expr);

    return (0);
}