The at command is used to schedule commands to be executed once at a particular time in the future. More precisely, it reads a series of commands from standard input and collects them into one "at-job" which is carried out at a later date. It is found in the Unix family of operating systems and other flavors as well. In computing, a command is a directive to a computer program acting as an interpreter of some kind, in order to perform a specific task. ... The standard streams are a set of input and output channels featured in Unix and Unix-like operating systems, and provided by the standard I/O library (stdio. ...
at can be made to mail a user when done carrying out a scheduled job of theirs, can use more than one job queue, and can read a list of jobs to carry out from a file instead of standard input.
It uses a daemon, atd, which waits in the background periodically checking the list of jobs to do and executing those at their allotted time on behalf of at. It can be made to only run scheduled jobs if the system's load average is below a certain value. In Unix and other computer operating systems, a daemon is a particular class of computer program that runs in the background, rather than under the direct control of a user; they are usually instantiated as processes. ... Load, in computing, is a measure of the amount of processing a computer system is currently performing, usually in the form of a scalar and as some variation on a percentage. ...
Surname redirect crontab ... Developed by Dave Zarzycki at Apple Computer, launchd is a unified framework for starting, stopping and managing daemons and other programs. ... Jump to: navigation, search Apple Computer, Inc. ...
External links
[1] The program's manpage Almost all substantial UNIX and Unix-like operating systems have extensive documentation available as an electronic manual, split into multiple sections called man pages (short for manual pages and based on the command used to display them). ...
Unix or UNIX is a computer operating system originally developed in the 1960s and 1970s by a group of ATandT Bell Labs employees including Ken Thompson, Dennis Ritchie, and Douglas McIlroy.
The Unix systems are characterized by various concepts: plain text files, command line interpreter, hierarchical file system, treating devices and certain types of inter-process communication as files, etc. In software engineering, Unix is mainly noted for its use of the C programming language and for the Unix philosophy.
During the late 1970s and early 1980s, Unix's influence in academic circles led to massive adoption (particularly of the BSD variant, originating from the University of California, Berkeley) of Unix by commercial startups, the most notable of which is Sun Microsystems.
UNIX® (or Unix) is a portable, multi-task and multi-user computer operating system originally developed by a group of AT&T Bell Labs employees including Ken Thompson, Dennis Ritchie and Douglas McIlroy.
The UNIX trademark and the certification rights were sold to the X/Open Consortium, which was an industry group to define a "UNIX Standard".
The command prompt with which users interacted was just an ordinary user-level process, a UNIX shell.
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