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- AT User Commands AT
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- NNAAMMEE
- at - execute commands at a later time
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- SSYYNNOOPPSSIISS
- aatt [[ --cc ]] [[ --ss ]] [[ --mm ]] time [ day ] [ file ]
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- DDEESSCCRRIIPPTTIIOONN
- _A_t spools away a copy of the named _f_i_l_e to be used as input
- to _s_h(1) or _c_s_h(1). If the --cc flag (for (_c_s_h(1))) or the --ss
- flag (for (_s_h(1))) is specified, then that shell will be
- used to execute the job; if no shell is specified, the
- current environment shell is used. If no file name is
- specified, _a_t prompts for commands from standard input until
- a ^D is typed.
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- If the --mm flag is specified, mail will be sent to the user
- after the job has been run. If errors occur during execution
- of the job, then a copy of the error diagnostics will be
- sent to the user. If no errors occur, then a short message
- is sent informing the user that no errors occurred.
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- The format of the spool file is as follows: A four line
- header that includes the owner of the job, the name of the
- job, the shell used to run the job, and whether mail will be
- set after the job is executed. The header is followed by a
- _c_d command to the current directory and a _u_m_a_s_k command to
- set the modes on any files created by the job. Then _a_t
- copies all relevant environment variables to the spool file.
- When the script is run, it uses the user and group ID of the
- creator of the spool file.
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- The _t_i_m_e is 1 to 4 digits, with an optional following `A',
- `P', `N' or `M' for AM, PM, noon or midnight. One and two
- digit numbers are taken to be hours, three and four digits
- to be hours and minutes. If no letters follow the digits, a
- 24 hour clock time is understood.
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- The optional _d_a_y is either (1) a month name followed by a
- day number, or (2) a day of the week; if the word `week'
- follows, invocation is moved seven days further off. Names
- of months and days may be recognizably truncated. Examples
- of legitimate commands are
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- at 8am jan 24
- at -c -m 1530 fr week
- at -s -m 1200n week
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- _A_t programs are executed by periodic execution of the com-
- mand /usr/lib/atrun from _c_r_o_n(8). The granularity of _a_t
- depends upon the how often atrun is executed.
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- Error output is lost unless redirected or the -_m flag is
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- AT User Commands AT
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- requested, in which case a copy of the errors is sent to the
- user via _m_a_i_l(1).
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- FFIILLEESS
- /usr/spool/at spooling area
- /usr/spool/at/yy.ddd.hhhh.* job file
- /usr/spool/at/past directory where jobs are executed from
- /usr/spool/at/lasttimedone last time atrun was run
- /usr/lib/atrun executor (run by cron(8))
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- SSEEEE AALLSSOO
- atq(1), atrm(1), calendar(1), sleep(1), cron(8)
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- DDIIAAGGNNOOSSTTIICCSS
- Complains about various syntax errors and times out of
- range.
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- BBUUGGSS
- Due to the granularity of the execution of /_u_s_r/_l_i_b/_a_t_r_u_n,
- there may be bugs in scheduling things almost exactly 24
- hours into the future.
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- If the system crashes, mail is not sent to the user inform-
- ing them that the job was not completed.
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- Sometimes old spool files are not removed from the directory
- /usr/spool/at/past. This is usually due to a system crash,
- and requires that they be removed by hand.
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- Sprite v1.0 March 20, 1986 2
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