at(1) at(1)NAME at, batch - execute commands at a later time SYNOPSIS at time [date] [+increment] at -l [job...] at -r job... batch DESCRIPTION at and batch read commands from standard input to be execut- ed at a later time. at allows you to specify when the com- mands should be executed, while jobs queued with batch will execute when system load level permits. at -r removes jobs previously scheduled with at. The -l flag option reports all jobs scheduled for the invoking user. Standard output and standard error output are mailed to the user via mail(1) unless they are redirected elsewhere. The shell environment variables, current directory, umask, and ulimit are retained when the commands are executed. Open file descriptors, traps, and priority are lost. Users are permitted to use at if their name appears in the file /usr/lib/cron/at.allow. If that file does not exist, the file /usr/lib/cron/at.deny is checked to determine if the user should be denied access to at. If neither file ex- ists, only root is allowed to submit a job. The allow/deny files consist of one user name per line. The time may be specified as 1, 2, or 4 digits. One and two digit numbers are taken to be hours, four digits to be hours and minutes. The time may alternately be specified as two numbers separated by a colon, meaning hour:minute. A suffix am or pm may be appended; otherwise a 24-hour clock time is understood. The suffix zulu may be used to indicate GMT. The special names noon, midnight, now, and next are also recognized. An optional date may be specified as either a month name followed by a day number (and possibly year number preceded by an optional comma) or a day of the week (fully spelled or abbreviated to three characters). Two special days, today and tomorrow are recognized. If no date is given, today is assumed if the given hour is greater than the current hour and tomorrow is assumed if it is less. If the given month is less than the current month (and no year is given), next year is assumed. The optional increment is simply a number suffixed by one of the following: minutes, hours, days, weeks, months, or years. (The singular form is also accepted.) April, 1990 1
at(1) at(1)Thus legitimate commands include: at 0815am Jan 24 at 8:15am Jan 24 at now + 1 day at 5 pm Friday at and batch write the job number and schedule time to stan- dard error. batch submits a batch job. It is similar to at now, but goes into a different queue, and will respond more promptly with any error messages. at -r removes jobs previously scheduled by at or batch. The job number is the number given to you previously by the at or batch command. You can also get job numbers by typing at -l. You can remove only your own jobs unless you are the superuser. EXAMPLES The at and batch commands read from standard input the com- mands to be executed at a later time. sh(1) provides dif- ferent ways of specifying standard input. Within your com- mands, it may be useful to redirect standard output. This sequence can be used at a terminal: batch nroff filename > outfile CONTROL-d This sequence, which demonstrates redirecting standard error to a pipe, is useful in a shell procedure (the sequence of output redirection specifications is significant): batch <<! nroff filename 2>&1 > outfile | mail loginid ! To have a job reschedule itself, invoke at from within the shell procedure, by including code similar to the following within the shell file: echo "sh shellfile" | at 1900 thursday next week If the machine is down at the scheduled time, the job is not run. FILES /usr/bin/at /usr/bin/batch 2 April, 1990
at(1) at(1)/usr/lib/atrun executor (run by cron(1M) /usr/lib/cron main cron directory /usr/lib/cron/at.allow list of allowed users /usr/lib/cron/at.deny list of denied users /usr/lib/cron/queuedefs scheduling information /usr/spool/cron/atjobs spool area SEE ALSO crontab(1), kill(1), mail(1), nice(1), ps(1), sh(1), cron(1M). DIAGNOSTICS Complaints about various syntax errors and times out of range. April, 1990 3