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cron 1.9 KB

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  1. .TH CRON 8
  2. .SH NAME
  3. cron \- clock daemon
  4. .SH SYNOPSIS
  5. .B auth/cron
  6. [
  7. .B -c
  8. ]
  9. .SH DESCRIPTION
  10. .I Cron
  11. executes commands at specified dates and times according
  12. to instructions in the files
  13. .BI /cron/ user /cron\f1.
  14. It runs only on an authentication server.
  15. Option
  16. .B -c
  17. causes
  18. .I cron
  19. to create
  20. .BI /cron/ user
  21. and
  22. .BI /cron/ user /cron
  23. for the current user;
  24. it can be run from any Plan 9 machine.
  25. .PP
  26. Blank lines and lines beginning with
  27. .B #
  28. in these files are ignored.
  29. Entries are lines with fields
  30. .IP
  31. .I
  32. minute hour day month weekday host command
  33. .PP
  34. .I Command
  35. is a string, which may contain spaces, that is passed to an
  36. .IR rc (1)
  37. running on
  38. .I host
  39. for execution.
  40. The first five fields are integer patterns for
  41. .PD0
  42. .RS
  43. .TP \w'month\ of\ year\ \ 'u
  44. minute
  45. 0\-59
  46. .TP
  47. hour
  48. 0\-23
  49. .TP
  50. day of month
  51. 1\-31
  52. .TP
  53. month of year
  54. 1\-12
  55. .TP
  56. day of week
  57. 0\-6; 0=Sunday
  58. .PD
  59. .RE
  60. .PP
  61. The syntax for these patterns is
  62. .IP
  63. .EX
  64. time : '*'
  65. | range
  66. range : number
  67. | number '-' number
  68. | range ',' range
  69. .EE
  70. .PP
  71. Each number must be in the appropriate range.
  72. Hyphens specify inclusive ranges of valid times;
  73. commas specify lists of valid time ranges.
  74. .PP
  75. To run the job,
  76. .I cron
  77. calls
  78. .I host
  79. and authenticates remote execution, equivalent to running
  80. .B rx
  81. .I host
  82. .I command
  83. (see
  84. .IR con (1)).
  85. The user's profile is run with
  86. .B $service
  87. set to
  88. .BR rx .
  89. If
  90. .I host
  91. is
  92. set to
  93. .BR local ,
  94. .I cron
  95. will run the command as
  96. .I user
  97. on the local machine without using
  98. .BR rx .
  99. .PP
  100. .I Cron
  101. is not a reliable service.
  102. It skips commands if it cannot reach
  103. .I host
  104. within two minutes, or if the
  105. .I cron
  106. daemon is
  107. not running at the appropriate time.
  108. .SH EXAMPLES
  109. Here is the job that mails system news.
  110. .IP
  111. .EX
  112. % cat /cron/upas/cron
  113. # send system news
  114. 15 8-17,21 * * * helix /mail/lib/mailnews
  115. %
  116. .EE
  117. .SH FILES
  118. .TF /cron/lock
  119. .TP
  120. .B /cron/lock
  121. lock file to prevent multiple
  122. .IR cron s
  123. running
  124. .SH SOURCE
  125. .B /sys/src/cmd/auth/cron.c
  126. .SH "SEE ALSO"
  127. .IR con (1),
  128. .IR rc (1)