Format
- at [–m] [–f file]
[–q queue] –t time
- at [–m] [–f file]
[–q queue] timespec
- at –r [–q queue] at_job
…
- at –l [–q queue]
[at_job …]
Description
at lets
you set up a series of commands to be run later. It reads the commands
from the standard input (stdin) or from a file specified with the –f option.
When the commands run, they have the same environment variables, working
directory, file creation mask, and so on that are set up when you
run the at command; however, at does
not typically preserve open file descriptors, traps, or priority inherited
from the working environment.
Typically, you redirect the standard
output (stdout) from these commands to files so you can read the files
after the system runs the commands. at mails
the standard output (stdout) and standard error output (stderr) to
you if you do not redirect them.
The at command
displays an at-job identifier when you submit
commands, along with the time that the system is to run the commands.
at, batch,
and crontab submit jobs to cron;
the data in these jobs may contain double-byte characters. When the
jobs are run, the data in the jobs are interpreted in the locale that cron is
using. Since it is strongly recommended that cron be
started in the POSIX locale, double-byte characters in the job may
not be interpreted correctly. You can get around this by calling setlocale() in
the job itself.
Options
- –f file
- Reads commands from file rather than
from standard input (stdin).
- –l
- Reports on standard output (stdout) all jobs you have scheduled
and when the system is to run them if you do not specify at_job.
Specifying at_job reports information about
those jobs only.
- –m
- Sends you mail after your job has finished running. If you did
not redirect the stdout and stderr, at also
mails these to you. If stdout or stderr is non-null, at mails
this output to you even if you do not specify –m.
- –q queue
- Specifies the queue your at job is to
be recorded in or removed from. queue can
be any single-byte character except a space, a tab, a null character,
or a number sign (#). By default, at stores
all its jobs in a queue called a, and batch stores
all its jobs in a queue called b. If used with this
option, –l only reports information about at jobs
in queue.
- –r at_job
- Removes previously scheduled at jobs.
The at_job arguments must be the identifiers
assigned to the jobs when you set them up with at.
- –t time
- Specifies the time for the system to run the job. You specify time in
the same format as the time argument for touch.
When you do not use the
–t option,
you can use a
timespec argument to specify
the time. A
timespec argument consists of
three parts: a time, a date, and an increment (in that order). You
must always specify the time, but you can omit the date, the increment,
or both. Following are possible time formats:
- Format
- Meaning
- hhmm
- hh hours, mm minutes,
24-hour clock
- hh:mm
- hh hours, mm minutes,
24-hour clock
- h:mm
- h hours, mm minutes,
24-hour clock
- h:m
- h hours, m minutes,
24-hour clock
- hh:mm zone
- zone is time zone
- hh:mmam
- Morning, 12-hour clock
- hh:mmam zone
- Morning, 12-hour clock in given time zone
- hh:mmpm
- Afternoon, 12-hour clock
- hh:mmpm zone
- Afternoon, 12-hour clock in given time zone
- noon
- Noon
- midnight
- Midnight
- next
- The current time, next day that meets date and increment
- now
- The current time today
All minute specifications are optional. For
example, to specify an
at job to run at
1:00 p.m., you can enter
at 1pm
Currently,
the z/OS shell only
supports the time zones GMT, CUT, UTC, and ZULU, all of which stand
for Coordinated Universal Time (often called Greenwich Mean Time).
If you do not specify a zone, at interprets
times with respect to the TZ environment variable.
Format of the TZ environment variable explains how to set the local time zone
with the TZ environment variable.
Possible date formats are
shown in the following list:
- Format
- Meaning
- month day
- month is the full name, or the three-letter
abbreviation (as in January or Jan)
- month day, year
- day and year given
as appropriate numbers
- weekday
- weekday is the full name or the three-letter
abbreviation (as in Monday or Mon)
- today
- The current day
- tomorrow
- Next day
The increment is added to the time and date
you specify with the preceding parts of
timespec.
It has the format
+ n units where
n is
a number and
units is one of the following:
minute minutes hour hours
day days week weeks
month months year years
Here are some sample
time specifications:
0655
1855
18:55
6:55pm
6:55 pm Jan 10
now + 3 hours
noon tomorrow
midnight Friday
Environment variables
at uses
the following environment variables:
- SHELL
- Contains
the name of the shell used to invoke the at job.
- TZ
- Specifies
the default time zone for all times given on the command line. If
you include a time zone as part of time or timespec,
it overrides the value of TZ. Format of the TZ environment variable explains
how to set the local time zone with the TZ environment variable.
Usage notes
at jobs
that contain a line consisting of just the string "!!!ATEOF!!!" fail
with unexpected results.
Localization
at uses
the following localization variables:
- LANG
- LC_ALL
- LC_CTYPE
- LC_MESSAGES
- LC_TIME
- NLSPATH
The keywords
midnight,
noon,
today,
and
tomorrow are valid only in the
POSIX locale.
See Localization for more information.
Exit values
- 0
- Successful completion
- >0
- Returned if the command fails for any reason
If an error occurs, at does
not schedule, remove, or list the job.
Portability
POSIX.2 User Portability Extension, UNIX
systems.
Related information
batch, bg, cron, crontab, touch, tcsh