Access element of nested struct

Question

In C, is it possible to have a struct nested within another struct? How would I access the fields of the inner struct? Take the struct for kinfo_proc for example:

struct kinfo_proc {
  struct  extern_proc kp_proc;      /* proc structure */
  struct  eproc {
    struct  proc *e_paddr;    /* address of proc */
    struct  session *e_sess;  /* session pointer */
    struct  _pcred e_pcred;   /* process credentials */
    struct  _ucred e_ucred;   /* current credentials */
    struct   vmspace e_vm;    /* address space */
    pid_t e_ppid;     /* parent process id */
    pid_t e_pgid;     /* process group id */
    short e_jobc;     /* job control counter */
    dev_t e_tdev;     /* controlling tty dev */
    pid_t e_tpgid;    /* tty process group id */
    struct  session *e_tsess; /* tty session pointer */
#define WMESGLEN  7
    char  e_wmesg[WMESGLEN+1];  /* wchan message */
    segsz_t e_xsize;    /* text size */
    short e_xrssize;    /* text rss */
    short e_xccount;    /* text references */
    short e_xswrss;
    int32_t e_flag;
#define EPROC_CTTY  0x01  /* controlling tty vnode active */
#define EPROC_SLEADER 0x02  /* session leader */
#define COMAPT_MAXLOGNAME 12
    char  e_login[COMAPT_MAXLOGNAME]; /* short setlogin() name */
#if CONFIG_LCTX
    pid_t e_lcid;
    int32_t e_spare[3];
#else
    int32_t e_spare[4];
#endif
  } kp_eproc;
};

How would I go about trying to get the e_ppid of a newly made kinfo_proc instance?

rob mayoff · Accepted Answer · 2012-08-09 20:04:35Z

4

You would be creating something like :

struct kinfo_proc test1;
test1.kp_eproc.e_ppid /// Access it like this.

edited Aug 9, 2012 at 20:04

rob mayoff

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answered Aug 9, 2012 at 19:59

S.P.

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2 Comments

rollingcodes Over a year ago

i see your logic! i was missing the struct keyword. silly me. but i think "eproc" should actually be kp_eproc. when i did that it worked like a charm. thanks!

S.P. Over a year ago

Thanks Rob. He has changed it accordingly.

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