The queue implements a "thread"-safe mechanism for exchanging messages between multiple processes. Messages exchanged via queues will be received in the same order that they were sent.
| Function | Purpose |
|---|---|
| queue_destroy() | Remove a queue |
| queue_foreach() | Execute a callback for each message in a queue |
| queue_get() | Get a message from a queue |
| queue_init() | Create a new queue |
| queue_put() | Insert a message into a queue |
Remove a queue
queue_destroy "$queue"
The queue_destory() function removes the queue referenced by $queue.
| Return value | Meaning |
|---|---|
| 0 | The queue was successfully removed |
| 1 | The queue could not be removed |
This function does not read from standard input.
This function does not write to standard output.
This function does not write to standard error.
Execute a callback for each message in a queue
queue_foreach "$queue" "$func" "${args[@]}"
The queue_foreach() function executes the callback $func once for each message contained in the queue
referenced by $queue. The callback will be passed the message in the first parameter, followed by the
elements in $args.
If the callback returns a non-zero value, queue_foreach() will not visit the remaining messages in the
queue.
| Return value | Meaning |
|---|---|
| 0 | The callback successfully processed all messages |
| 1 | The queue could not be locked, or the callback failed |
This function does not read from standard input.
This function does not write to standard output.
This function does not write to standard error.
Get a message from a queue
queue_get "$queue" "$timeout"
The queue_get() function will return the message from the head of the queue $queue. If the queue is empty,
the function will wait for at least $timeout seconds for the arrival of a message. If $timeout was
omitted, the function will wait indefinitely; if $timeout is zero, the function will return immediately.
| Return value | Meaning |
|---|---|
| 0 | A message was successfully retrieved from the queue |
| 1 | Could not retrieve a message from the queue |
This function does not read from standard input.
Upon success, the message retrieved from the queue is written to standard output. Otherwise, no data is written to standard output.
This function does not write to standard error.
Create a new queue
queue_init "$queue"
The queue_init() function initializes a new queue with path $queue. If $queue is a relative path, the
queue will be created in the home directory of the executing user.
| Return value | Meaning |
|---|---|
| 0 | The queue was successfully created |
| 1 | The queue could not be created |
This function does not read from standard input.
This function does not write to standard output.
This function does not write to standard error.
Insert a message into a queue
queue_put "$queue" "$item"
The queue_put() function places the item $item in the queue referenced by $queue.
| Return value | Meaning |
|---|---|
| 0 | The item was successfully inserted |
| 1 | The item could not be inserted |
This function does not read from standard input.
This function does not write to standard output.
This function does not write to standard error.