| at | |
|---|---|
 TheReactOS 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 |
at is ashellcommand for scheduling commands to be executed at a futuretime; once. The command was developed forUnix and is available onUnix andUnix-like systems,Windows,[1] andReactOS.[2]
On Unix-like operating systems,at reads a series of commands fromstandard 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 sameworking directory and with the sameenvironment variables set as when it was scheduled. It differs fromcron, which is used for recurring executions (e.g. once an hour, every Tuesday, January 1 every year). As withcron, many Unix systems allow the administrator to restrict access to theat command.at can be made to mail a user when done carrying out a scheduled job, can use more than onejob queue, and can read a list of jobs to carry out from afile instead of standard input. The Linuxat command was mostly written by Thomas Koenig.[3]
Thebatch command can be used instead ofat to only run scheduled jobs if the system'sload average is below a certain value.
A sample command to compile aC program at 11:45 a.m. on January 31 would be:
$echo"cc -o foo foo.c"|at1145jan31
or
$at1145jan31at> cc -o foo foo.cat> ^D #(press Control-D while at the beginning of a line)
Theatq program lists the currently queued jobs, whileatrm removes jobs from the queue:
$atq1234 2011-08-12 11:45 cc -o foo foo.c user$atrm1234$atq$
In some Unix-like computeroperating systems, it uses adaemon,atd, which waits in the background periodically checking the list of jobs to do and executing those at their scheduled time on behalf ofat.
In addition to thegraphical user interface forWindows Task Scheduler inControl Panel, Windows provides anat shell command that schedules operations to run at a specified time and date (similar tocron). It is available sinceWindows NT, but is now deprecated in favor ofschtasks. It can only be used when theSchedule service is running. When used without parameters,at lists scheduled commands.[4]at cannot access tasks created or modified by Control Panel orschtasks.exe.[5] Also, tasks created withat are not interactive by default; interactivity needs to be explicitly requested.[6]
TheReactOS implementation is based on the Windows implementation. It was developed by Eric Kohl and is licensed under theGPLv2.[2]
To useat, 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]\\ ComputerNameID/delete/yeshours : minutes/interactive/every:date/next:command/?
at: execute commands at a later time – Shell and Utilities Reference,The Single UNIX Specification, Version 5 fromThe Open Groupbatch: schedule commands to be executed in a batch queue – Shell and Utilities Reference,The Single UNIX Specification, Version 5 fromThe Open Group| File system | |
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