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Annotation of coherent/a/usr/man/COHERENT/cron, revision 1.1.1.1

1.1       root        1: 
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                      3: cron                    System Maintenance                   cron
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                      8: Execute commands periodically
                      9: 
                     10: /etc/cron&
                     11: 
                     12: cron is  a daemon  that executes  commands at preset  times.  The
                     13: commands and their scheduled execution times are kept in the file
                     14: /usr/lib/crontab.
                     15: 
                     16: Once each minute cron searches through crontab.  For each command
                     17: stored there,  cron compares the current  time with the scheduled
                     18: execution time and executes the command if the times match.  When
                     19: it  finishes  the  search, cron  sleeps  until  the next  minute.
                     20: Because it  never exits, cron should be  executed only once (cus-
                     21: tomarily by /etc/rc).
                     22: 
                     23: crontab consists of  lines separated by newlines.  Each line con-
                     24: sists of  six fields separated  by white space  (tabs or blanks).
                     25: The first  five fields describe  the scheduled execution  time of
                     26: the  command.  Respectively,  they represent  the  minute (0-59),
                     27: hour (0-23),  day of the month (1-31), month  of the year (1-12),
                     28: and day  of the week  (0-6, 0 indicates Sunday).   Each field may
                     29: contain a single integer in  the appropriate range, a pair of in-
                     30: tegers separated  by a hyphen  `-' (meaning all  integers between
                     31: the two, inclusive),  an asterisk `*' (meaning all legal values),
                     32: or a  comma-separated list of the above  forms.  The remainder of
                     33: the line gives the command to be executed at the given time.
                     34: 
                     35: For example, the ccrroonnttaabb entry
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                     37: 
                     38:         29 * * 7 0 msg henry Succotash!
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                     41: means  that every  hour on  the half-hour  during each  Sunday in
                     42: July,  ccrroonn will invoke the command mmssgg, and the user named hheennrryy
                     43: will have the message
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                     46:         daemon: Succotash!
                     47: 
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                     49: written on his terminal's screen (if he is logged in).
                     50: 
                     51: cron recognizes three  special characters and escape sequences in
                     52: the crontab.   If a command  contains the percent  character `%',
                     53: cron executes only  the portion up to the first  `%' as a command
                     54: and passes  the remainder to  the command as  its standard input.
                     55: cron translates  any percent characters  `%' in the  remainder to
                     56: newlines.  The special  interpretation of `%' can be prevented by
                     57: preceding it  with a backslash, `\%'.   Finally, cron removes the
                     58: sequence \<nneewwlliinnee> from the  text before passing it to the shell
                     59: sh;  this can  be  used to  make  an entry  in  the crontab  more
                     60: legible.
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                     63: 
                     64: COHERENT Lexicon                                           Page 1
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                     68: 
                     69: cron                    System Maintenance                   cron
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                     72: 
                     73: cron is  designed for commands  that must be  executed regularly.
                     74: Temporal commands  that need to  be executed only  once should be
                     75: handled with the command at.
                     76: 
                     77: ***** Files *****
                     78: 
                     79: /uussrr/lliibb/ccrroonnttaabb for stored commands
                     80: 
                     81: ***** See Also *****
                     82: 
                     83: at, init, system maintenance
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                    130: COHERENT Lexicon                                           Page 2
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