AT(1) | General Commands Manual | AT(1)

# NAME

`at`, `batch` — queue, examine or delete jobs for later execution

# SYNOPSIS

`at` | [`-bm`] [`-f` file] [`-l` [job ...]] [`-q` queue] `-t` time_arg | timespec

`at` | `-c` | `-r` job ...

`batch` | [`-m`] [`-f` file] [`-q` queue] [timespec]

# DESCRIPTION

`at` and `batch` read commands from standard input or a specified file which are to be executed at a later time, via the user's shell as specified by the `SHELL` environment variable. If `SHELL` is not set, the shell in the user's password database entry is used instead. If all else fails, sh(1) will be used.

The related programs are as follows:

`at`
  Executes commands at a specified time.
`batch`
  Executes commands when system load levels permit. In other words, when the load average drops below 1.5, or the value specified in the invocation of cron(8).

The options are as follows:

`-b`
  An alias for `batch`.
`-c` job ...
  Prints the jobs listed on the command line to standard output.
`-f` file
  Reads the job from file rather than standard input.
`-l` [job ...]
  Displays the queue of jobs which are currently awaiting execution. If a job argument is specified, only the specified jobs will be displayed. Unless the user is the superuser, only the user's own jobs will be displayed.
`-m`
  Send mail to the user when the job has completed, even if there was no output.
`-q` queue
  Uses the specified queue. A queue designation consists of a single letter. Valid queue designations range from a to z and A to Z. The c queue is the default for `at` and the E queue for `batch`. Queues with higher letters run with increased niceness. If a job is submitted to a queue designated with an uppercase letter, it is treated as if it had been submitted to batch at that time. If the user specified the `-l` option and `at` is given a specific queue, only jobs pending in that queue will be shown.
`-r` job ...
  Remove the specified job(s) from the `at` queue.
`-t` time_arg
  Specify the job time. The argument should be of the form [[cc]yy]mmddHHMM[.SS] (matching touch(1)'s `-t` format), where the parts of the argument represent the following:

  ccyy
    Year. If yy is specified, but cc is not, a value for yy between 69 and 99 results in a cc value of 19. Otherwise, a cc value of 20 is used.
  mm
    Month: a number from 1 to 12.
  dd
    Day: a number from 1 to 31.
  HH
    Hour: a number from 0 to 23.
  MM
    Minute: a number from 0 to 59.
  SS
    Second: a number from 0 to 60 (permitting a leap second), preceded by a period. The default is 0.
timespec
  As well as the `-t` option, `at` alternatively allows some moderately complex timespec specifications. It accepts times of the form HHMM or HH:MM to run a job at a specific time of day (if that time is already past, the next day is assumed). It is also possible to specify `midnight`, `noon`, `now`, or `teatime` (4pm), or have a time-of-day suffixed with `AM` or `PM` for running in the morning or the evening. To say what day the job will be run, give a date in the form month-name day with an optional year, or giving a date of the form dd.mm.ccyy, dd.mm.yy, mm/dd/ccyy, mm/dd/yy, mmddccyy, or mmddyy.

  The year may be given as two or four digits. If the year is given as two digits, it is taken to occur as soon as possible in the future, which may be in the next century — unless it's last year, in which case it's considered to be a typo.

  The specification of a date must follow the specification of the time of day. A time like [`now`] `+` count time-units may be given, where the time-units can be `minutes`, `hours`, `days`, `weeks`, `months`, or `years` (the singular forms are also accepted). To tell `at` to run the job today or tomorrow, suffix the time with `today` or `tomorrow`. The `next` keyword may be used as an alias for `+ 1`.

  For example, to run a job at 4pm three days from now, use `at 4pm + 3 days`. To run a job at 10:00am on July 31, use `at 10am Jul 31`. To run a job at 1am tomorrow, use `at 1am tomorrow`. To run a job at midnight in one week's time, use `at midnight next week`.

For both `at` and `batch`, commands are read from standard input (or the file specified with the `-f` option) and executed. The working directory, the environment (except for the variables `BASH_VERSINFO`, `DISPLAY`, `EUID`, `GROUPS`, `PPID`, `SHELLOPTS`, `SSH_AGENT_PID`, `SSH_AUTH_SOCK`, `TERM`, `TERMCAP`, `UID`, and `_`), and the umask are retained from the time of invocation. An `at` or `batch` command invoked from a su(1) shell will retain the current user ID. The user will be mailed standard error and standard output from his commands, if any. If `at` is executed from a su(1) shell, the owner of the login shell will receive the mail.

For non-root users, permission to run `at` is determined by the files /var/cron/at.allow and /var/cron/at.deny. Note: these files must be readable by group crontab (if they exist).

If the file /var/cron/at.allow exists, only usernames mentioned in it are allowed to use `at`. If /var/cron/at.allow does not exist, /var/cron/at.deny is checked. Every username not mentioned in it is then allowed to use `at`. If neither exists, only the superuser is allowed to run `at`.

An empty /var/cron/at.deny means that every user is allowed to use these commands. This is the default configuration.

# FILES

/var/cron/atjobs
  directory containing job files
/var/cron/at.allow
  allow permission control
/var/cron/at.deny
  deny permission control

# EXIT STATUS

The `at` utility exits with one of the following values:

0
  Jobs were successfully submitted, removed, or listed.
>0
  An error occurred.

# SEE ALSO

atq(1), atrm(1), nice(1), sh(1), touch(1), umask(2), cron(8)

# STANDARDS

The `at` and `batch` utilities are compliant with the specification.

The `at` flags [`-bc`] and the `teatime` timespec are extensions to that specification.

states that `batch` is equivalent to running "`at -q b -m now`". This implementation permits a timespec argument, as well as the ability to read from a file (`-f`) and specify a job queue (`-q`), and does not send mail to the user (`-m`) by default.

By default, schedules `at` jobs in queue a and `batch` jobs in queue b.

The at.allow/deny mechanism is marked by as being an X/Open System Interfaces option.

# AUTHORS

`at` was mostly written by Thomas Koenig <ig25@rz.uni-karlsruhe.de>. The time parsing routines are by David Parsons <orc@pell.chi.il.us>.

# BUGS

`at` and `batch` as presently implemented are not suitable when users are competing for resources.

November 5, 2024 | Debian