ham_attach()

Synopsis:

#include <ha/ham.h>

ham_entity_t *ham_attach( const char *ename, 
                          int reserved,
                          pid_t pid,  
                          const char *line, 
                          unsigned flags );

Arguments:

ename

The name of the entity; it must be unique across the whole context of the HAM.

reserved

Set this argument to 0.

pid

Process ID to attach to, if the process is already running. If pid ≤ 0, the HAM starts the process and begins monitoring it. In this case, line must also be specified with the FULL path (including all required arguments) to start the process.

line

This contains the FULL command line, including arguments, to start the process. This is used ONLY if pid ≤ 0 and is ignored otherwise. If either the pathname or the arguments contain spaces that need to be passed literally to the spawn call, they need to be quoted. As long as the subcomponents within the path arguments are quoted, using either of the following methods:

\'path with space\'

or:

\"path with space\",

the following is allowed:

"\'path with space\' arg1 arg2 \"arg3 with space\"".

This would be parsed as:

"path with space" -> path

arg1 = arg1

arg2 = arg2

arg3 = "arg3 with space".

flags

Currently, the following flag is defined:

HENTITYKEEPONDEATH: Indicates that the entity and all it conditions will be retained when the entity dies and is not restarted. The default is to remove all entities that aren't restarted.

Library:

libham

Description:

You use the ham_attach() function to attach an entity to the HAM. An entity can be any process on the system. You can use this function to:

attach a process that's already running
or:
tell the HAM to start a process and then add it as an entity to its context.

Once an entity has been attached, you can add conditions and actions to it.

Note:

Since the ham_attach() function opens a temporary connection to the HAM, it also calls ham_connect() and ham_disconnect() internally. So any client that makes a ham_attach() call doesn't need to call ham_connect() or ham_disconnect() before and after the call to ham_attach(), unless they want to call another API function that depends on a permanent connection to the HAM already being available. For instance, a client must call ham_connect() explicitly if they plan to call ham_condition(), because the latter function uses a file descriptor that gets created by the former function.

Returns:

A valid handle to an entity on success; otherwise, NULL (errno is set).

Errors:

EBADF: Couldn't connect to the HAM.
EEXIST: The name provided for the entity already exists.
EINVAL: The name given in ename is invalid (e.g., it contains the / character) or is NULL.
The pid provided is ≤ 0, but no line was provided or the line provided is too long, i.e., it exceeds _POSIX_PATH_MAX (defined in <limits.h>).
ENAMETOOLONG: The name given (in ename) is too long, i.e., it exceeds _POSIX_PATH_MAX (defined in <limits.h>). Note that the combined length of an entity/condition/action name is also limited by _POSIX_PATH_MAX.
ENOENT: (QNX Neutrino 7.0 or later) There isn't a process with the specified pid.
ENOMEM: Not enough memory to create a new handle.

In addition to the above errors, the HAM returns any error it encounters while servicing the request to add a new entity to its context.

Classification:

QNX OS


Safety:
Cancellation point	No
Signal handler	No
Thread	Yes