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Annotation of coherent/a/usr/man/COHERENT/at.c, revision 1.1

1.1     ! root        1: 
        !             2: 
        !             3: at                           Command                           at
        !             4: 
        !             5: 
        !             6: 
        !             7: 
        !             8: Execute commands at given time
        !             9: 
        !            10: aatt [ -vv ] [ -cc _c_o_m_m_a_n_d ] _t_i_m_e [ [ _d_a_y ] wweeeekk ] [ _f_i_l_e ]
        !            11: aatt [ -vv ] [ -cc _c_o_m_m_a_n_d ] _t_i_m_e _m_o_n_t_h _d_a_y [ _f_i_l_e ]
        !            12: 
        !            13: at executes commands at a given time in the future.
        !            14: 
        !            15: If the -c option is  used, aatt executes the following command.  If
        !            16: file  is named,  at reads  the commands from  it.  If  neither is
        !            17: given, at reads the standard input for commands.
        !            18: 
        !            19: If time  is a one-digit or two-digit number,  aatt interprets it as
        !            20: specifying an hour.  If  time is a three-digit or four-digit num-
        !            21: ber, aatt interprets it as specifying an hour and minutes.  If _t_i_m_e
        !            22: is followed  by aa, pp, nn,  or mm, at assumes AAMM,  PPMM, nnoooonn, or mmiidd-
        !            23: nniigghhtt, respectively; otherwise,  it assumes that time indicates a
        !            24: 24-hour clock.
        !            25: 
        !            26: For example, the command
        !            27: 
        !            28: 
        !            29:         at -c "time | msg henry" 1450
        !            30: 
        !            31: 
        !            32: set the ttiimmee  command to be executed at 2:50  PM, and pipe ttiimmee's
        !            33: output to the mmssgg command, which  will pass it to the terminal of
        !            34: user  hheennrryy.  Note  that  argument to  the  -cc option  had to  be
        !            35: enclosed  in  quotation  marks  because  it contains  spaces  and
        !            36: special characters;  if this were not done, aatt  would not be able
        !            37: to tell  when the argument ended, and so  would generate an error
        !            38: message.  Also note that if you wish pass information to a user's
        !            39: terminal with  the aatt command, you  must tell aatt to  whom to send
        !            40: the information.  The command
        !            41: 
        !            42: 
        !            43:         at 250p commandfile
        !            44: 
        !            45: 
        !            46: will set the file ccoommmmaannddffiillee to be read and executed at 2:50 PM.
        !            47: Note that it  is _n_o_t necessary to use the  file's full path name.
        !            48: Also, if  the suffix pp  were not appended  to the time,  the file
        !            49: would be set to be read at 2:50 AM.
        !            50: 
        !            51: The time set in aatt's command  line is _n_o_t the exact time that the
        !            52: command is  executed.  Rather, the daemon cron  wakes up the file
        !            53: /usr/lib/atrun  periodically to  see  if any  commands have  been
        !            54: scheduled commands  to be executed  at or before  that time.  The
        !            55: frequency   with  which  cron   executes  atrun   determines  the
        !            56: ``granularity''  of at  execution  times; it  may  be changed  by
        !            57: editing the file /usr/lib/crontab.  For example, the entry
        !            58: 
        !            59: 
        !            60: 
        !            61: 
        !            62: 
        !            63: 
        !            64: COHERENT Lexicon                                           Page 1
        !            65: 
        !            66: 
        !            67: 
        !            68: 
        !            69: at                           Command                           at
        !            70: 
        !            71: 
        !            72: 
        !            73:         0,5,10,15,20,25,30,35,40,45,50,55 * * * *   /usr/lib/atrun
        !            74: 
        !            75: 
        !            76: sets /uussrr/lliibb/aattrruunn to be executed every five minutes.  Thus, the
        !            77: aatt command that is set, for  example, to 2:53 PM will actually be
        !            78: executed at  2:55 PM.  atrun executes  specified commands when it
        !            79: discovers that the given time is past; therefore, at commands are
        !            80: executed even if  the system is down at the  specified time or if
        !            81: the system's time is changed.
        !            82: 
        !            83: The aatt command has two forms, as shown above.  In the first form,
        !            84: the option day names a day of the week (lower case, spelled out).
        !            85: If week  is specified,  at interprets the  given time and  day as
        !            86: meaning that  time and day the following  week.  For example, the
        !            87: command
        !            88: 
        !            89: 
        !            90:         at -c "time | msg henry" 1450 friday week
        !            91: 
        !            92: 
        !            93: executes ttiimmee  and sends its output to  hheennrryy's terminal one week
        !            94: from Friday at 2:50 PM.
        !            95: 
        !            96: In  the second  form given  above, month  specifies a  month name
        !            97: (lower case,  spelled out) and the number day  specifies a day of
        !            98: the month.  For example, the command
        !            99: 
        !           100: 
        !           101:         at 1450 july 4 commandfile
        !           102: 
        !           103: 
        !           104: set the file ccoommmmaannddffiillee to be read at 2:50 PM on July 4.
        !           105: 
        !           106: If the  -v flag is  given, at prints  the time when  the commands
        !           107: will be  executed, giving you enough information  to plan for the
        !           108: execution of  the command.  For example, if it  is now August 13,
        !           109: 1990, at 2:30 PM, and you type the command
        !           110: 
        !           111: 
        !           112:         at -v -c "/usr/games/fortune | msg henry" 1435
        !           113: 
        !           114: 
        !           115: aatt will reply:
        !           116: 
        !           117: 
        !           118:         Tue Aug 13 14:35:00
        !           119: 
        !           120: 
        !           121: indicating that  the command will  be executed five  minutes from
        !           122: now.  However, if you type
        !           123: 
        !           124: 
        !           125: 
        !           126: 
        !           127: 
        !           128: 
        !           129: 
        !           130: COHERENT Lexicon                                           Page 2
        !           131: 
        !           132: 
        !           133: 
        !           134: 
        !           135: at                           Command                           at
        !           136: 
        !           137: 
        !           138: 
        !           139:         at -v -c "/usr/games/fortune | msg henry" 1435 august 10
        !           140: 
        !           141: 
        !           142: aatt will reply
        !           143: 
        !           144: 
        !           145:         Sun Aug 10 14:35:00 1991
        !           146: 
        !           147: 
        !           148: which indicates  that on Sunday, August 10 of  next year, at 2:35
        !           149: PM, the COHERENT system will print a ffoorrttuunnee onto your terminal.
        !           150: 
        !           151: Should you  create such a long-distance aatt  file by accident, you
        !           152: can correct the error by simply deleting the file that encodes it
        !           153: from the  directory /uussrr/ssppooooll/aatt.  The file  will be named after
        !           154: the time  that it is set to execute,  plus a unique two-character
        !           155: suffix, should  more than one command be scheduled  to run at the
        !           156: same time.  For example, the  file for the above command would be
        !           157: named 99110088110011443355.aaaa.
        !           158: 
        !           159: Finally, note that  the current working directory, exported shell
        !           160: variables, file creation mask, user id, and group id are restored
        !           161: when the given command is executed.
        !           162: 
        !           163: ***** Files *****
        !           164: 
        !           165: /bbiinn/ppwwdd -- To find current directory
        !           166: /uussrr/lliibb/aattrruunn -- Execute scheduled commands
        !           167: /uussrr/ssppooooll/aatt -- Scheduled activity directory
        !           168: /uussrr/ssppooooll/aatt/ _y_y_m_m_d_d_h_h_m_m._x_x -- Commands scheduled at given time
        !           169: 
        !           170: ***** See Also *****
        !           171: 
        !           172: at, commands, cron
        !           173: 
        !           174: 
        !           175: 
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        !           195: 
        !           196: COHERENT Lexicon                                           Page 3
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