cc [ flag... ] file... -lpctx [ library... ]
#include <libpctx.h>

typedef enum {
 PCTX_NULL_EVENT = 0,
 PCTX_SYSC_EXEC_EVENT,
 PCTX_SYSC_FORK_EVENT,
 PCTX_SYSC_EXIT_EVENT,
 PCTX_SYSC_LWP_CREATE_EVENT,
 PCTX_INIT_LWP_EVENT,
 PCTX_FINI_LWP_EVENT,
 PCTX_SYSC_LWP_EXIT_EVENT
} pctx_event_t;

typedef int pctx_sysc_execfn_t(pctx_t *pctx, pid_t pid, id_t lwpid,
 char *cmd, void *arg);

typedef void pctx_sysc_forkfn_t(pctx_t *pctx,
 pid_t pid, id_t lwpid, pid_t child, void *arg);

typedef void pctx_sysc_exitfn_t(pctx_t *pctx, pid_t pid, id_t lwpid,
 void *arg);

typedef int pctx_sysc_lwp_createfn_t(pctx_t *pctx, pid_t pid, id_t lwpid,
 void *arg);

typedef int pctx_init_lwpfn_t(pctx_t *pctx, pid_t pid, id_t lwpid,
 void *arg);

typedef int pctx_fini_lwpfn_t(pctx_t *pctx, pid_t pid, id_t lwpid,
 void *arg);

typedef int pctx_sysc_lwp_exitfn_t(pctx_t *pctx, pid_t pid, id_t lwpid,
 void *arg);

int pctx_set_events(pctx_t *pctx...);

The pctx_set_events() function allows the caller (the controlling process) to express interest in various events in the controlled process. See pctx_capture(3CPC) for information about how the controlling process is able to create, capture and manipulate the controlled process.

The pctx_set_events() function takes a pctx_t handle, followed by a variable length list of pairs of pctx_event_t tags and their corresponding handlers, terminated by a PCTX_NULL_EVENT tag.

Most of the events correspond closely to various classes of system calls, though two additional pseudo-events (init_lwp and fini_lwp) are provided to allow callers to perform various housekeeping tasks. The init_lwp handler is called as soon as the library identifies a new LWP, while fini_lwp is called just before the LWP disappears. Thus the classic "hello world" program would see an init_lwp event, a fini_lwp event and (process) exit event, in that order. The table below displays the interactions between the states of the controlled process and the handlers executed by users of the library.

Each of the handlers is passed the caller's opaque handle, a pctx_t handle, the pid, and lwpid of the process and lwp generating the event. The lwp_exit, and (process) exit events are delivered before the underlying system calls begin, while the exec, fork, and lwp_create events are only delivered after the relevant system calls complete successfully. The exec handler is passed a string that describes the command being executed. Catching the fork event causes the calling process to fork(2), then capture the child of the controlled process using pctx_capture(\|) before handing control to the fork handler. The process is released on return from the handler.

Upon successful completion, pctx_set_events(\|) returns 0. Otherwise, the function returns -1.

Example 1 HandleExec example.

This example captures an existing process whose process identifier is pid, and arranges to call the HandleExec routine when the process performs an exec(2).

static void
HandleExec(pctx_t *pctx, pid_t pid, id_t lwpid, char *cmd, void *arg)
{
 (void) printf("pid %d execed '%s'\en", (int)pid, cmd);
}
int
main()
{
 ...
 pctx = pctx_capture(pid, NULL, 1, NULL);
 (void) pctx_set_events(pctx,
 PCTX_SYSC_EXEC_EVENT, HandleExec,
 ...
 PCTX_NULL_EVENT);
 (void) pctx_run(pctx, 0, 0, NULL);
 pctx_release(pctx);
}

See attributes(5) for descriptions of the following attributes:

exec(2), exit(2), fork(2), vfork(2), fork1(2), cpc(3CPC), libpctx(3LIB), proc(4), attributes(5)