z/OS V1R9.0 UNIX System Services Command ... - Christian Grothoff

When matching the date and time expressions given in crontab entries, cron uses
the time zone in effect when the system started the daemon. As a result, you
should ensure that the TZ environment variable is set at this time. For information
on setting the TZ environment variable, see Appendix I. For at jobs, cron uses the
value of TZ in effect when you submitted the job.
at, batch, and crontab submit jobs to cron; the data for those jobs can contain
doublebyte characters. When the jobs are executed, the data in the jobs are
interpreted in the locale that cron is using. Because it is strongly recommended that
cron be started in the POSIX locale, doublebyte characters in the jobs may not be
interpreted correctly. You can get around this by calling the setlocale() system call
in the job itself.
The crontab, batch, and at job files store information about the MVS identity and
the UNIX identity (the real UID) of the user who created the jobs. The cron daemon
uses that information to set up the environment in which to run the jobs as follows:
v the MVS identity is set to the user’s MVS identity.
v the UNIX real and effective UIDs are set to the user’s real UID.
cron handles the following externally generated signals in a special way:
SIGTERM
Causes cron to exit. You can cause cron to exit with the following
command:
kill –TERM pid
where pid is the cron’s PID number. To find the cron’s PID number, you can
use:
ps -e | grep cron
SIGUSR1
Is sent by either at or crontab to indicate a new at job or an updated
crontab entry. cron does not delete at jobs until they finish running. If the
cron daemon is terminated while at jobs are running, cron runs them again
when the daemon is restarted.
SIGUSR2
Writes internal cron queue information to the log file.
The following is an example of output to a cron log from ’kill -USR2 5’. The
output was written to the log on a test system when the queuedefs job limit of 5
was exceeded. The number of jobs that are running is 5 (the limit is 500):
Queue `c’ 5j2n15w:
queued 4, running 5, jobs 5
Next try for queued jobs 13 seconds
RUNNING: uid/gid: 0/512: pid 33554441: sleep 10000 RUNNING: uid/gid: 0/512:
pid 385875972: echo start; sleep 10000; echo end RUNNING: uid/gid: 0/512: pid
67108876: echo start; sleep 10000; echo end RUNNING: uid/gid: 0/512: pid
33554445: echo start; sleep 10000; echo end RUNNING: uid/gid: 0/512: pid
67108879: echo start; sleep 10000; echo end QUEUED: uid/gid: 0/512: echo Hello!
QUEUED: uid/gid: 0/512: echo start; sleep 10000; echo end
QUEUED: uid/gid: 0/512: echo Hello!
QUEUED: uid/gid: 0/512: echo start; sleep 10000; echo end
cron uses a number of files in the /usr/lib/cron directory to determine which users
may and may not use the at and crontab commands.
v The file at.allow contains the list of users who have permission to use at.
cron daemon
v The file at.deny contains the list of users who do not have permission to use at.
Chapter 2. Shell command descriptions 169