名字

at, batch, atq, atrm - 排隊、檢查或刪除以后要執行的作業。  

總覽

at [-V] [-q 隊列] [-f 文件] [-mldbv] 時間 at -c 作業 [作業...] atq [-V] [-q 隊列] [-v]
atrm [-V] 作業 [作業...]
batch [-V] [-q 隊列] [-f 文件] [-mv] [時間]  

描述

at 和 batch 從標準輸入或一個指定的文件讀取命令，這些命令在以后某個時間用 /bin/sh 執行。

at

在指定的時間執行命令。

atq

列出用戶的等待執行的作業；在用戶是超級用戶的情況下，列出所有人的作業。

atrm

刪除作業。

batch

在系統負載水平允許的時候執行命令；換句話說，當平均負載降到低于0.8，或降到了在 atrun 文件中指定的期望值時運行。譯注：atrun 文件參見 atd 手冊頁。

At 允許相當復雜的時間指定，它擴展了 POSIX.2 標準。它接受 HH:MM 的時間式樣，用來指定在一天的某個時間運行一個作業。 (如果時間已經過了則假定為第二天。)你可以指定 midnight (午夜)、 noon (中午) 或 teatime (下午4點)，你可以用 AM 或 PM 后綴指定一天的上午或下午。你可以給出 month-name day 加上可選的年份的式樣用來指定運行 at 的日期，或者給出 MMDDYY 、 MM/DD/YY 或 DD.MM.YY 式樣用來指定運行 at 的日期。日期的指定必須跟在時間指定的后面。你也可以給出象 now + 計數 時間單位 的式樣，這里的時間單位可以是 minutes 、 hours 、 days 或 weeks， 你可以給時間加一個 today 后綴來指定 at 今天運行作業，可以給時間加一個 tomorrow 后綴來指定 at 明天運行作業。

例如，要在三天以后的下午 4 點運行一個作業，at 時間參數可以指定為 4pm + 3 days。 要在7月31日上午10:00運行一個作業， at 時間參數可以指定為 10am Jul 31， 要在明天上午1點運行一個作業，at 時間參數可以指定為 1am tomorrow。

時間指定的精確的定義可以在 /usr/doc/at-3.1.7/timespec 找到。

對于 at 和 batch 兩者，從標準輸入或以 -f 選項指定的文件中讀取命令并執行之。工作路徑、環境變量(除了 TERM、 DISPLAY 和 _)、 umask 從所期望的時間起保持不變。從一個從執行 su(1) 命令得到的 shell 中調用的 at - 或 batch - 命令將保持當前的 userid。用戶的命令的標準錯誤輸出和標準輸出將用郵件發給用戶。發送郵件使用命令 /usr/sbin/sendmail。 從一個從執行 su(1)命令得到的 shell 中執行了 at ，登錄 shell 的所有者將接到郵件。 譯注：userid 是用戶標識的意思。umask 是與每個進程相關聯的文件方式創建屏蔽字。

超級用戶可以在任何情況下使用這些命令。對于其他用戶，使用 at 的權限由文件 /etc/at.allow 和 /etc/at.deny 確定。

如果文件 /etc/at.allow 存在，在其中提及的用戶名被允許使用 at 命令。

如果 /etc/at.allow 不存在，而 /etc/at.deny 存在，所有在 /etc/at.deny 中未提及的用戶被允許使用 at 命令。

如果兩者均不存在，只用超級用戶可以使用 at 命令。

一個空的 /etc/at.deny 意味著所有用戶均被允許使用這些命令，這是缺省的配置。

選項

-V

在標準錯誤上輸出版本號。

-q queue

使用指定的隊列。一個隊列用一個字母標定，有效的的隊列標定的范圍是從a到z和從A到Z。at 的缺省隊列是 a,batch 的缺省隊列是 b。隊列的字母順序越高，則隊列運行時越謙讓(運行級別越低)。指定的隊列 "=" 保留給當前運行的作業所在的隊列。 如果一個作業被提交到一個以大寫字母標定的隊列，則與提交到 batch 同樣對待。如果給 atq 指定一個隊列，則只顯示在此指定隊列中的作業。

-m

當作業完成時即使沒有輸出也給用戶發郵件。

-f file

從文件而不是標準輸入中讀取作業信息。

-l

是 atq 的別名。

-d

是 atrm 的別名。

-v

對于 atq， 顯示完整的在隊列中未被刪除的作業，對于其他命令，顯示作業將要執行的時間。 顯示的時間的格式類似于"1997-02-20 14:50"，但如果設置了 POSIXLY_CORRECT 環境變量之后，格式類似于"Thu Feb 20 14:50:00 1996"。

-c

連接命令行中列出的作業并輸出到標準輸出。

相關文件

/var/spool/at
/var/spool/at/spool
/proc/loadavg
/var/run/utmp
/etc/at.allow
/etc/at.deny  

參見

cron(1), nice(1), sh(1), umask(2), atd(8)

#p#

NAME

at, batch, atq, atrm - queue, examine or delete jobs for later execution  

SYNOPSIS

at [-V] [-q queue] [-f file] [-mldbv] TIME
at [-V] [-q queue] [-f file] [-mldbv] -t time_arg
at -c job [job...]
atq [-V] [-q queue]
atrm [-V] job [job...]
batch [-V] [-q queue] [-f file] [-mv] [TIME]  

DESCRIPTION

at and batch read commands from standard input or a specified file which are to be executed at a later time .

at

executes commands at a specified time.

atq

lists the user's pending jobs, unless the user is the superuser; in that case, everybody's jobs are listed. The format of the output lines (one for each job) is: Job number, date, hour, job class.

atrm

deletes jobs, identified by their job number.

batch

executes commands when system load levels permit; in other words, when the load average drops below 0.8, or the value specified in the invocation of atrun.

At allows fairly complex time specifications, extending the POSIX.2 standard. It accepts times of the form HH:MM to run a job at a specific time of day. (If that time is already past, the next day is assumed.) You may also specify midnight, noon, or teatime (4pm) and you can have a time-of-day suffixed with AM or PM for running in the morning or the evening. You can also say what day the job will be run, by giving a date in the form month-name day with an optional year, or giving a date of the form MMDDYY or MM/DD/YY or DD.MM.YY. The specification of a date must follow the specification of the time of day. You can also give times like now + count time-units, where the time-units can be minutes, hours, days, or weeks and you can tell at to run the job today by suffixing the time with today and to run the job tomorrow by suffixing the time with tomorrow.

For example, to run a job at 4pm three days from now, you would do at 4pm + 3 days, to run a job at 10:00am on July 31, you would do at 10am Jul 31 and to run a job at 1am tomorrow, you would do at 1am tomorrow.

The exact definition of the time specification can be found in /usr/share/doc/at-3.1.8/timespec.

For both at and batch, commands are read from standard input or the file specified with the -f option and executed. The working directory, the environment (except for the variables TERM, DISPLAY and _) and the umask are retained from the time of invocation. An at - or batch - command invoked from a su(1) shell will retain the current userid. The user will be mailed standard error and standard output from his commands, if any. Mail will be sent using the command /usr/sbin/sendmail. If at is executed from a su(1) shell, the owner of the login shell will receive the mail.

The superuser may use these commands in any case. For other users, permission to use at is determined by the files /etc/at.allow and /etc/at.deny.

If the file /etc/at.allow exists, only usernames mentioned in it are allowed to use at.

If /etc/at.allow does not exist, /etc/at.deny is checked, every username not mentioned in it is then allowed to use at.

If neither exists, only the superuser is allowed use of at.

An empty /etc/at.deny means that every user is allowed use these commands, this is the default configuration.  

OPTIONS

-V

prints the version number to standard error.

-q queue

uses the specified queue. A queue designation consists of a single letter; valid queue designations range from a to z. and A to Z. The a queue is the default for at and the b queue for batch. Queues with higher letters run with increased niceness. The special queue "=" is reserved for jobs which are currently running. If a job is submitted to a queue designated with an uppercase letter, it is treated as if it had been submitted to batch at that time. If atq is given a specific queue, it will only show jobs pending in that queue.

-m

Send mail to the user when the job has completed even if there was no output.

-f file

Reads the job from file rather than standard input.

-l

Is an alias for atq.

-d

Is an alias for atrm.

-v

Shows the time the job will be executed. Times displayed will be in the format "1997-02-20 14:50" unless the environment variable POSIXLY_CORRECT is set; then, it will be "Thu Feb 20 14:50:00 1997".

-c

cats the jobs listed on the command line to standard output.

-t time_arg

Submit the job to be run at the time specified by the time_arg option argument, which must have the same format as specified for the touch(1) utility's -t time option argument ([[CC]YY]MMDDhhmm).

ENVIRONMENT

SHELL

The value of the SHELL environment variable at the time of at invocation will determine which shell is used to execute the at job commands. If SHELL is unset when at is invoked, the user's login shell will be used; otherwise, if SHELL is set when at is invoked, it must contain the path of a shell interpreter executable that will be used to run the commands at the specified time. at will record the values of environment variables present at time of at invocation. When the commands are run at the specified time, at will restore these variables to their recorded values . These variables are excluded from this processing and are never set by at when the commands are run :
TERM, DISPLAY, SHELLOPTS, _, PPID, BASH_VERSINFO, EUID, UID, GROUPS.
If the user submitting the at job is not the super-user, variables that alter the behaviour of the loader ld.so(8), such as LD_LIBRARY_PATH , cannot be recorded and restored by at .

FILES

/var/spool/at
/var/spool/at/spool
/proc/loadavg
/var/run/utmp
/etc/at.allow
/etc/at.deny  

SEE ALSO

cron(1), nice(1), sh(1), umask(2), atd(8).