batch - schedule commands to be executed in a batch queue
The batch utility shall read commands from standard input and schedule them for execution in a batch queue. It shall be the equivalent of the command:
at -q b -m now
where queue b is a special at queue, specifically for batch jobs. Batch jobs shall be submitted to the batch queue with no time constraints and shall be run by the system using algorithms, based on unspecified factors, that may vary with each invocation of batch.
Users shall be permitted to use batch 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 shall be checked to determine whether the user shall be denied access to batch. If neither file exists, only a process with the appropriate privileges shall be allowed to submit a job. If only at.deny exists and is empty, global usage shall be permitted. The at.allow and at.deny files shall consist of one user name per line.
The standard input shall be a text file consisting of commands acceptable to the shell command language described in Shell Command Language .
The text files /usr/lib/cron/at.allow and /usr/lib/cron/at.deny shall contain zero or more user names, one per line, of users who are, respectively, authorized or denied access to the at and batch utilities.
The following environment variables shall affect the execution of batch:
LANG Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of IEEE Std 1003.1-2001, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.)
LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables.
SHELL Determine the name of a command interpreter to be used to invoke the at-job. If the variable is unset or null, sh shall be used. If it is set to a value other than a name for sh, the implementation shall do one of the following: use that shell; use sh; use the login shell from the user database; any of the preceding accompanied by a warning diagnostic about which was chosen.
When standard input is a terminal, prompts of unspecified format for each line of the user input described in the STDIN section may be written to standard output.
The following shall be written to standard error when a job has been successfully submitted:
“job %s at %s\n", at_job_id, <date>
where date shall be equivalent in format to the output of:
date +"%a %b %e %T %Y"
The date and time written shall be adjusted so that they appear in the timezone of the user (as determined by the TZ variable).
Neither this, nor warning messages concerning the selection of the command interpreter, are considered a diagnostic that changes the exit status.
Diagnostic messages, if any, shall be written to standard error.
The following exit values shall be returned:
The job shall not be scheduled.
The following sections are informative.
It may be useful to redirect standard output within the specified commands.
1. This sequence can be used at a terminal:
sort < file >outfile
2. This sequence, which demonstrates redirecting standard error to a pipe, is useful in a command procedure (the sequence of output redirection specifications is significant):
! diff file1 file2 2>&1 >outfile | mailx mygroup !
Early proposals described batch in a manner totally separated from at, even though the historical model treated it almost as a synonym for at -qb. A number of features were added to list and control batch work separately from those in at. Upon further reflection, it was decided that the benefit of this did not merit the change to the historical interface.
The -m option was included on the equivalent at command because it is historical practice to mail results to the submitter, even if all jobproduced output is redirected. As explained in the RATIONALE for at, the now keyword submits the job for immediate execution (after scheduling delays), despite some historical systems where at now would have been considered an error.
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .
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