 The ReactOS at command | |
| Developer(s) | Thomas Koenig, Microsoft, ReactOS Contributors |
|---|---|
| Written in | Unix-like, ReactOS: C |
| Operating system | Unix-like, Windows, ReactOS |
| Type | Command |
| License | Windows: Proprietary software ReactOS: GPLv2 |
In computing, at is a command in Unix-like operating systems, Microsoft Windows, [1] and ReactOS [2] used to schedule commands to be executed once, at a particular time in the future.
On Unix-like operating systems, at reads a series of commands from standard input and collects them into one "at-job" which is carried out at a later date. The job inherits the current environment, so that it is executed in the same working directory and with the same environment variables set as when it was scheduled. It differs from cron , which is used for recurring executions (e.g. once an hour, every Tuesday, January 1 every year). As with cron, many Unix systems allow the administrator to restrict access to the at command. at can be made to mail a user when done carrying out a scheduled job, can use more than one job queue, and can read a list of jobs to carry out from a file instead of standard input. The Linux at command was mostly written by Thomas Koenig. [3]
In addition to the graphical user interface for Windows Task Scheduler in Control Panel, Windows provides an at.exe command that schedules commands and programs to run on a computer at a specified time and date (similar to cron ). It is available since Windows NT, but is now deprecated in favor of schtasks . It can only be used when the Schedule service is running. When used without parameters, at.exe lists scheduled commands. [4] at.exe cannot access tasks created or modified by Control Panel or schtasks.exe. [5] Also, tasks created with at.exe are not interactive by default; interactivity needs to be explicitly requested. [6]
The ReactOS implementation is based on the Windows variant. It was developed by Eric Kohl and is licensed under the GPLv2. [2]
A sample command to compile a C program at 11:45 a. m. on January 31 would be:
$ echo"cc -o foo foo.c"|at1145jan31or
$ at1145jan31at> cc -o foo foo.cat> ^D #(press Control-D while at the beginning of a line)The atq program lists the currently queued jobs, while atrm removes jobs from the queue:
$ atq 1234 2011-08-12 11:45 cc -o foo foo.c user$ atrm1234$ atq $In some Unix-like computer operating systems, it uses a daemon, atd, which waits in the background periodically checking the list of jobs to do and executing those at their scheduled time on behalf of at.
The batch command can be used instead of at to only run scheduled jobs if the system's load average is below a certain value.
To use at.exe, the user must be a member of the local Administrators group.
The command-syntax is:
at [\\ComputerName] [{[ID] [/delete]|/delete [/yes]}]
at [[\\ComputerName] hours:minutes [/interactive] [{/every:date[,...]|/next:date[,...]}] command]
\\ ComputerName – This parameter specifies a remote computer. If it is omitted, at schedules the commands and programs on the local computer.ID – This parameter specifies the identification number assigned to a scheduled command./delete – This parameter cancels a scheduled command. If ID is omitted, all of the scheduled commands on the computer are canceled./yes – This parameter answers yes to all queries from the system when you delete scheduled events.hours : minutes – This parameter specifies the time when to run the command./interactive – This parameter allows the given command to interact with the desktop of the user who is logged on at the time command runs./every: – This parameter runs the given command on every specified day or days of the week or month.date – This parameter specifies the date when to run the given command. One or more days of the week can be specified. If date is omitted, at uses the current day of the month./next: – This parameter runs command on the next occurrence of the day.command – This parameter specifies the Windows command, program (that is, .exe or .com file), or batch program (that is, .bat or .cmd file) that will be run./? – Displays help for the command.Computerized batch processing is a method of running software programs called jobs in batches automatically. While users are required to submit the jobs, no other interaction by the user is required to process the batch. Batches may automatically be run at scheduled times as well as being run contingent on the availability of computer resources.
In computing, rmdir is a command which will remove an empty directory on various operating systems.
On many computing platforms everything is a file, but in contrast in IBM i everything is an object.
The cron command-line utility is a job scheduler on Unix-like operating systems. Users who set up and maintain software environments use cron to schedule jobs, also known as cron jobs, to run periodically at fixed times, dates, or intervals. It typically automates system maintenance or administration—though its general-purpose nature makes it useful for things like downloading files from the Internet and downloading email at regular intervals.
DIGITAL Command Language (DCL) is the standard command language adopted by many of the operating systems created by Digital Equipment Corporation. DCL had its roots in IAS, TOPS-20, and RT-11 and was implemented as a standard across most of Digital's operating systems, notably RSX-11 and RSTS/E, but took its most powerful form in VAX/VMS. DCL continues to be developed by VSI as part of OpenVMS.
nslookup is a network administration command-line tool for querying the Domain Name System (DNS) to obtain the mapping between domain name and IP address, or other DNS records.
Command Prompt, also known as cmd.exe or cmd, is the default command-line interpreter for the OS/2, eComStation, ArcaOS, Microsoft Windows, and ReactOS operating systems. On Windows CE .NET 4.2, Windows CE 5.0 and Windows Embedded CE 6.0 it is referred to as the Command Processor Shell. Its implementations differ between operating systems, but the behavior and basic set of commands are consistent. cmd.exe is the counterpart of COMMAND.COM in DOS and Windows 9x systems, and analogous to the Unix shells used on Unix-like systems. The initial version of cmd.exe for Windows NT was developed by Therese Stowell. Windows CE 2.11 was the first embedded Windows release to support a console and a Windows CE version of cmd.exe. The ReactOS implementation of cmd.exe is derived from FreeCOM, the FreeDOS command line interpreter.
A job scheduler is a computer application for controlling unattended background program execution of jobs. This is commonly called batch scheduling, as execution of non-interactive jobs is often called batch processing, though traditional job and batch are distinguished and contrasted; see that page for details. Other synonyms include batch system, distributed resource management system (DRMS), distributed resource manager (DRM), and, commonly today, workload automation (WLA). The data structure of jobs to run is known as the job queue.
In Windows NT operating systems, a Windows service is a computer program that operates in the background. It is similar in concept to a Unix daemon. A Windows service must conform to the interface rules and protocols of the Service Control Manager, the component responsible for managing Windows services. It is the Services and Controller app, services.exe, that launches all the services and manages their actions, such as start, end, etc.
Windows Vista contains a range of new technologies and features that are intended to help network administrators and power users better manage their systems. Notable changes include a complete replacement of both the Windows Setup and the Windows startup processes, completely rewritten deployment mechanisms, new diagnostic and health monitoring tools such as random access memory diagnostic program, support for per-application Remote Desktop sessions, a completely new Task Scheduler, and a range of new Group Policy settings covering many of the features new to Windows Vista. Subsystem for UNIX Applications, which provides a POSIX-compatible environment is also introduced.
Task Scheduler is a job scheduler in Microsoft Windows that launches computer programs or scripts at pre-defined times or after specified time intervals. Microsoft introduced this component in the Microsoft Plus! for Windows 95 as System Agent. Its core component is an eponymous Windows service. The Windows Task Scheduler infrastructure is the basis for the Windows PowerShell scheduled jobs feature introduced with PowerShell v3.
A batch file is a script file in DOS, OS/2 and Microsoft Windows. It consists of a series of commands to be executed by the command-line interpreter, stored in a plain text file. A batch file may contain any command the interpreter accepts interactively and use constructs that enable conditional branching and looping within the batch file, such as IF, FOR, and GOTO labels. The term "batch" is from batch processing, meaning "non-interactive execution", though a batch file might not process a batch of multiple data.
In computing, type is a command in various command-line interpreters (shells) such as COMMAND.COM, cmd.exe, 4DOS/4NT and Windows PowerShell used to display the contents of specified files on the computer terminal. The analogous Unix command is cat.
In computing, TIME is a command in DEC RT-11, DOS, IBM OS/2, Microsoft Windows and a number of other operating systems that is used to display and set the current system time. It is included in command-line interpreters (shells) such as COMMAND.COM, cmd.exe, 4DOS, 4OS2 and 4NT.
To shut down or power off a computer is to remove power from a computer's main components in a controlled way. After a computer is shut down, main components such as CPUs, RAM modules and hard disk drives are powered down, although some internal components, such as an internal clock, may retain power.
In computing, start is a command of the IBM OS/2, Microsoft Windows and ReactOS command-line interpreter cmd.exe to start programs or batch files or to open files or directories using the default program. start is not available as a standalone program. The underlying Win32 API is ShellExecute.
In computing, net is a command in IBM OS/2, Microsoft Windows, ReactOS and Greentea OS used to manage and configure the operating system from the command-line. It is also part of the IBM PC Network Program for DOS.
A command-line interface (CLI) is a means of interacting with a device or computer program with commands from a user or client, and responses from the device or program, in the form of lines of text. Such access was first provided by computer terminals starting in the mid-1960s. This provided an interactive environment not available with punched cards or other input methods.
forfiles is a computer software utility for Microsoft Windows, which selects files and runs a command on them. File selection criteria include name and last modified date. The command specifier supports some special syntax options. It can be used directly on the command-line, or in batch files or other scripts.
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