/**
* Executes the command, prints the result to the specified output stream and returns a success
* flag.
*
* @param ctx database context
* @param os output stream
* @return success flag. The {@link #info()} method returns information on a potential exception
*/
private boolean exec(final Context ctx, final OutputStream os) {
// check if data reference is available
final Data dt = ctx.data();
if (dt == null && data) return error(NO_DB_OPENED);
// check permissions
if (!ctx.perm(perm, dt != null ? dt.meta : null)) return error(PERM_REQUIRED_X, perm);
// set updating flag
updating = updating(ctx);
try {
// register process
ctx.register(this);
// run command and return success flag
return run(ctx, os);
} finally {
// guarantee that process will be unregistered
ctx.unregister(this);
}
}
