Functions
---------
+`child_process_init`::
+
+ Initialize a struct child_process variable.
+
`start_command`::
Start a sub-process. Takes a pointer to a `struct child_process`
The caller:
-1. allocates and clears (memset(&chld, 0, sizeof(chld));) a
- struct child_process variable;
+1. allocates and clears (using child_process_init() or
+ CHILD_PROCESS_INIT) a struct child_process variable;
2. initializes the members;
3. calls start_command();
4. processes the data;
. If the string does not contain '=', it names an environment
variable that will be removed from the child process's environment.
+If the .env member is NULL, `start_command` will point it at the
+.env_array `argv_array` (so you may use one or the other, but not both).
+The memory in .env_array will be cleaned up automatically during
+`finish_command` (or during `start_command` when it is unsuccessful).
+
To specify a new initial working directory for the sub-process,
specify it in the .dir member.