The at command is used for jobs that only need to be run once. These jobs are run from either the command line or from scripts. The at entries do not go in the crontab files.
prw------- 1 root cron 0 Jul 23 15:16 FIFO -rw-r----- 1 bin cron 4 Sep 30 1997 at.deny -rw-r----- 1 bin cron 3 Sep 30 1997 cron.deny -rw-rw-r-- 1 bin bin 272 Aug 05 11:27 log -rw-r--r-- 1 root sys 1328 Sep 18 1997 queuedefs
Following is an example of an error message found in the log file:
Out of disk space for a temporary file: There is not enough space in the file system. read: no such file or directory
EventType.[Jobsj][Nicen][Waitw]Refer to the man page on the queuedefs file for additional information.
crontab -eThis starts an editing session for the /var/spool/cron/crontabs/user_id file. By default, the vi editor is used. If the EDITOR environment variable is set, that editor is used.
Any lines beginning with a pound sign (#) are comments and are ignored.
A crontab entry consists of six fields:
The specification of days may be made by two fields (day of the month and day of the week). If you specify both as a list of elements, both are adhered to. For example:
0 0 1,15 * 1 commandThis entry would run command on the first and fifteenth days of each month, as well as every Monday. To specify days by only one field, the other field should contain an "*" (asterisk).
For example, to run the date command at 2 a.m. on Monday:
0 2 * * 1 /bin/dateThe parameters can also be specified as a range with a dash (-), as in 1-5, or a list separated by commas, as in 1,2,3,4,5. For more information on crontab entries, see the man page for the crontab command.
* * * * * /bin/dateThen check your mail. cron sends the output from standard out and standard error to the mailbox of the user submitting the job. You should receive the output of the date command once each minute. If you do not get mail back, check to see if the cron daemon is running. Enter the following:
ps -eaf |grep cronLook for a line where the last field is: /usr/sbin/cron or /etc/cron. If cron is not running, check the /etc/inittab file for an entry such as the following:
cron:2:respawn:/etc/cronIf you have this entry and cron is still not running, execute:
telinit qThen recheck using the ps command above to see if cron is running. If this still does not work, contact your support organization for assistance.
ps -eaf |grep cronThe output will look something like the following:
root 20294 1 0 Sep 26 - 4:18 /etc/cronThe number after root is the process ID (PID). Type kill -9 PID to stop cron and cause it to start and reread the crontabs files.
#!/bin/ksh cd $HOME . .profileThis will only pick up the environment variables that are set in the .profile file. To completely duplicate your environment, from the command line run the env command and explicitly set all the variables in the cron script with:
export VARIABLE_NAME=valueNOTE: For the Korn shell, other environment variables may be set in /etc/profile and, depending upon the setting of the ENV environment variable, the file pointed to the variable is also run. You may have to explicitly set all the variables you need in the cron script.
croutAxwAXAxBC8These files are created as temporary files in /tmp when cron runs a job. When the job finishes, the crout file is usually removed. If the files are still there, the cron daemon is failing half way through the job and is getting respawned by init. Therefore the job in question never completes.
To locate the bad job, check the timestamp. Enter the following:
ls -l crout*Match the output to the entry in the crontabs file to which it belongs.
cron_job_file >/dev/null 2>&1If you are running a script, you may have to individually redirect any commands inside the file that write to either standard error or standard out.
cron_job_file | mail user_nameYou may have to do this inside the script file to catch all occurrences of output.
If cron is running and you can get the output by running the date command in the test, the program or script is probably not running. See the section in this document called "A job runs from the command line but not from cron".
If you can see the job is running but you get no mail, test to see if you can send mail to the user submitting the cron job.
If you can send mail, the command or script probably is not outputting anything to standard out or standard error, or it is redirecting it somewhere else.
Commands submitted by the at command are actually run by the cron command.
The Date variable to the -t flag is specified using the following format:The digits in the Date variable are defined as follows:
For more information on using the -t flag, refer to the at command man page.
The most common way to submit a job is:
echo <command to execute> |at -t 950603220000or
echo <command to execute> |at now + 200 minutesSee the at command man page for a complete list of time, day, and increment parameters.
[ Doc Ref: 90605200014612 Publish Date: Oct. 20, 2000 4FAX Ref: 4925 ]