---
name: "queue"
section: "3tcl"
platform: "linux"
package: "tcllib"
version: "2.0+dfsg-4"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/queue/3tcl"
---

# queue(3tcl)

Create and manipulate queue objects

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```

## NAME

struct::queue - Create and manipulate queue objects

## SYNOPSIS

package require **Tcl 8.5 9**

package require **struct::queue ?1.4.6?**

*queueName* **option** ?*arg arg ...*?

*queueName* **clear**

*queueName* **destroy**

*queueName* **get** ?*count*?

*queueName* **peek** ?*count*?

*queueName* **put** *item* ?*item ...*?

*queueName* **unget** *item*

*queueName* **size**

```

```

## DESCRIPTION

The **::struct** namespace contains a commands for processing finite queues.

It exports a single command, **::struct::queue**. All functionality provided here can be reached through a subcommand of this command.

*Note:* As of version 1.4.1 of this package a critcl based C implementation is available. This implementation however requires Tcl 8.4 to run.

The **::struct::queue** command creates a new queue object with an associated global Tcl command whose name is *queueName*.  This command may be used to invoke various operations on the queue.  It has the following general form:

- *queueName* **option** ?*arg arg ...*?

  *Option* and the *arg*s determine the exact behavior of the command.  The following commands are possible for queue objects:

- *queueName* **clear**

  Remove all items from the queue.

- *queueName* **destroy**

  Destroy the queue, including its storage space and associated command.

- *queueName* **get** ?*count*?

  Return the front *count* items of the queue and remove them from the queue.  If *count* is not specified, it defaults to 1.  If *count* is 1, the result is a simple string; otherwise, it is a list.  If specified, *count* must be greater than or equal to 1. If there are not enough items in the queue to fulfull the request, this command will throw an error.

- *queueName* **peek** ?*count*?

  Return the front *count* items of the queue, without removing them from the queue.  If *count* is not specified, it defaults to 1. If *count* is 1, the result is a simple string; otherwise, it is a list.  If specified, *count* must be greater than or equal to 1. If there are not enough items in the queue to fulfull the request, this command will throw an error.

- *queueName* **put** *item* ?*item ...*?

  Put the *item* or items specified into the queue.  If more than one *item* is given, they will be added in the order they are listed.

- *queueName* **unget** *item*

  Put the *item* into the queue, at the front, i.e. before any other items already in the queue. This makes this operation the complement to the method **get**.

- *queueName* **size**

  Return the number of items in the queue.

## BUGS, IDEAS, FEEDBACK

This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category *struct :: queue* of the *Tcllib Trackers* \[http://core.tcl.tk/tcllib/reportlist\]. Please also report any ideas for enhancements you may have for either package and/or documentation.

When proposing code changes, please provide *unified diffs*, i.e the output of **diff -u**.

Note further that *attachments* are strongly preferred over inlined patches. Attachments can be made by going to the **Edit** form of the ticket immediately after its creation, and then using the left-most button in the secondary navigation bar.

## KEYWORDS

graph, list, matrix, pool, prioqueue, record, set, skiplist, stack, tree

## CATEGORY

Data structures