每天一个Linux命令（43）at命令

    at命令用于在指定时间执行命令。at允许使用一套相当复杂的指定时间的方法。可以用相对时间法指定，也可以用绝对时间法指定。

    (1)用法:

    用法:  at  [选项参数]  [时间]

    (2)功能:

    功能:  在指定的时间执行命令。

    (3)选项参数:

      1) -c　　　　　　　　　　显示即将执行任务的细节

      2) -d　　　　　　　　　  用任务id号删除指定的任务

      3) -l    　　　　　　　　  等同于atq，用job的id号显示指定的未删除而待执行的任务

    (4)实例: 

      1)[root@localhost sunjimeng]# at now + 1 minutes　　　　　  用相对时间，在一分钟之后执行命令

[root@localhost sunjimeng]# at now + 2 minutes
at> echo "I'm MenAngel!,I'm study at order!"
at> <EOT>
job 11 at Wed Jun 8 17:46:00 2016

      at> <EOT> 

      <这里输入 [ctrl] + d 就会出现 <EOF> 的字样代表结束! 

      当你输入下一个命令时，系统会自动提醒你，您在 /var/spool/mail/sunjimeng 中有邮件。此邮件中就包含这个命令执行的结果。

      2)[root@localhost sunjimeng]# at 17:47　　　　　　　　　　　在一个绝对时间执行一个命令

[root@localhost sunjimeng]# at 17:47
at> ls -l /home/sunjimeng/Documents
at> <EOT>
job 13 at Wed Jun  8 17:47:00 2016
您在 /var/spool/mail/sunjimeng 中有新邮件

      这里在语句的末尾提醒你有新邮件，可以用cat命令查看文件:/var/spool/mail/sunjimeng。

      3)[root@localhost sunjimeng]# atq　　　　　　　　　　　　　　计划任务设定后，在没有执行之前我们可以用atq命令来查看系统没有执行工作任务　　　　　　　　　　　

[root@localhost sunjimeng]# atq
1    Wed Jun  8 17:21:00 2016 a root
2    Wed Jun  8 17:23:00 2016 a root
3    Wed Jun  8 17:23:00 2016 a root
4    Wed Jun  8 17:26:00 2016 a root
5    Sat Jun 11 17:00:00 2016 a root
6    Wed Jun  8 17:31:00 2016 a root

      4)[root@localhost sunjimeng]# atq　　　　　　　　　　　　　　删除已经设置的任务

[root@localhost sunjimeng]# atq
1    Wed Jun  8 17:21:00 2016 a root
2    Wed Jun  8 17:23:00 2016 a root
3    Wed Jun  8 17:23:00 2016 a root
4    Wed Jun  8 17:26:00 2016 a root
5    Sat Jun 11 17:00:00 2016 a root
6    Wed Jun  8 17:31:00 2016 a root
[root@localhost sunjimeng]# atrm 1 2 3 4 5
[root@localhost sunjimeng]# atq
6    Wed Jun  8 17:31:00 2016 a root

    5)[root@localhost sunjimeng]# cat /var/spool/mail/sunjimeng　　　　　　显示at命令的执行结果　　

[root@localhost sunjimeng]# cat /var/spool/mail/sunjimeng
From root@localhost.localdomain  Wed Jun  8 17:46:01 2016
Return-Path: <root@localhost.localdomain>
X-Original-To: sunjimeng
Delivered-To: sunjimeng@localhost.localdomain
Received: by localhost.localdomain (Postfix, from userid 0)
    id 24622632F338; Wed,  8 Jun 2016 17:46:01 -0700 (PDT)
Subject: Output from your job       11
To: sunjimeng@localhost.localdomain
Message-Id: <20160609004601.24622632F338@localhost.localdomain>
Date: Wed,  8 Jun 2016 17:46:01 -0700 (PDT)
From: root@localhost.localdomain (root)

I'm MenAngel!,I'm study at order!

From root@localhost.localdomain  Wed Jun  8 17:47:00 2016
Return-Path: <root@localhost.localdomain>
X-Original-To: sunjimeng
Delivered-To: sunjimeng@localhost.localdomain
Received: by localhost.localdomain (Postfix, from userid 0)
    id C83A5632F338; Wed,  8 Jun 2016 17:47:00 -0700 (PDT)
Subject: Output from your job       13
To: sunjimeng@localhost.localdomain
Message-Id: <20160609004700.C83A5632F338@localhost.localdomain>
Date: Wed,  8 Jun 2016 17:47:00 -0700 (PDT)
From: root@localhost.localdomain (root)

总用量 0
drwxr-xr-x. 2 root root 72 5月  31 18:25 grepDir
-rw-r--r--. 1 root root  0 6月   7 23:34 myfile
drwxr-xr-x. 2 root root  6 6月   7 23:33 newWatch

From root@localhost.localdomain  Wed Jun  8 17:47:00 2016
Return-Path: <root@localhost.localdomain>
X-Original-To: sunjimeng
Delivered-To: sunjimeng@localhost.localdomain
Received: by localhost.localdomain (Postfix, from userid 0)
    id C9EA3632F33A; Wed,  8 Jun 2016 17:47:00 -0700 (PDT)
Subject: Output from your job       12
To: sunjimeng@localhost.localdomain
Message-Id: <20160609004700.C9EA3632F33A@localhost.localdomain>
Date: Wed,  8 Jun 2016 17:47:00 -0700 (PDT)
From: root@localhost.localdomain (root)

总用量 0
drwxr-xr-x. 2 root root 72 5月  31 18:25 grepDir
-rw-r--r--. 1 root root  0 6月   7 23:34 myfile
drwxr-xr-x. 2 root root  6 6月   7 23:33 newWatch

From root@localhost.localdomain  Wed Jun  8 17:52:01 2016
Return-Path: <root@localhost.localdomain>
X-Original-To: sunjimeng
Delivered-To: sunjimeng@localhost.localdomain
Received: by localhost.localdomain (Postfix, from userid 0)
    id F3239632F338; Wed,  8 Jun 2016 17:52:00 -0700 (PDT)
Subject: Output from your job       14
To: sunjimeng@localhost.localdomain
Message-Id: <20160609005200.F3239632F338@localhost.localdomain>
Date: Wed,  8 Jun 2016 17:52:00 -0700 (PDT)
From: root@localhost.localdomain (root)

I'm MenAngel

From root@localhost.localdomain  Wed Jun  8 17:54:00 2016
Return-Path: <root@localhost.localdomain>
X-Original-To: sunjimeng
Delivered-To: sunjimeng@localhost.localdomain
Received: by localhost.localdomain (Postfix, from userid 0)
    id 4B264632F338; Wed,  8 Jun 2016 17:54:00 -0700 (PDT)
Subject: Output from your job       15
To: sunjimeng@localhost.localdomain
Message-Id: <20160609005400.4B264632F338@localhost.localdomain>
Date: Wed,  8 Jun 2016 17:54:00 -0700 (PDT)
From: root@localhost.localdomain (root)

总用量 4
drwxr-xr-x. 2 sunjimeng sunjimeng    6 5月   1 01:23 Desktop
drwxrwxr-x. 4 sunjimeng users     4096 5月  28 00:24 Document
drwxr-xr-x. 4 root      sunjimeng   48 6月   7 23:34 Documents
drwxr-xr-x. 2 sunjimeng sunjimeng    6 5月   1 01:23 Downloads
drwxrwxr-x. 2 sunjimeng sunjimeng    6 5月  17 04:55 findTextDir
drwxr-xr-x. 2 sunjimeng sunjimeng    6 5月   1 01:23 Music
drwxr-xr-x. 2 sunjimeng sunjimeng    6 5月   1 01:23 Pictures
drwxr-xr-x. 2 sunjimeng sunjimeng    6 5月   1 01:23 Public
drwxr-xr-x. 2 sunjimeng sunjimeng    6 5月   1 01:23 Templates
drwxr-xr-x. 2 sunjimeng sunjimeng    6 5月   1 01:23 Videos

From root@localhost.localdomain  Wed Jun  8 17:54:00 2016
Return-Path: <root@localhost.localdomain>
X-Original-To: sunjimeng
Delivered-To: sunjimeng@localhost.localdomain
Received: by localhost.localdomain (Postfix, from userid 0)
    id 4E5D2632F33A; Wed,  8 Jun 2016 17:54:00 -0700 (PDT)
Subject: Output from your job       16
To: sunjimeng@localhost.localdomain
Message-Id: <20160609005400.4E5D2632F33A@localhost.localdomain>
Date: Wed,  8 Jun 2016 17:54:00 -0700 (PDT)
From: root@localhost.localdomain (root)

总用量 0
drwxr-xr-x. 2 root root 72 5月  31 18:25 grepDir
-rw-r--r--. 1 root root  0 6月   7 23:34 myfile
drwxr-xr-x. 2 root root  6 6月   7 23:33 newWatch

      6)[sunjimeng@localhost ~]$ at -c 18　　　　　　　　　　根据id号查看即将要执行命令的细节

[sunjimeng@localhost ~]$ atq                      //显示结果表明没有即将要执行的任务
[sunjimeng@localhost ~]$ at now + 1 minutes       //新建一个要执行的任务
at> ls -l
at> <EOT>
job 18 at Wed Jun  8 18:09:00 2016
[sunjimeng@localhost ~]$ atq                      //查看
18    Wed Jun  8 18:09:00 2016 a sunjimeng
[sunjimeng@localhost ~]$ at -c 18                //根据id号查看，它的即将执行的细节
#!/bin/sh
# atrun uid=1000 gid=1000
# mail sunjimeng 0
umask 2
XDG_VTNR=1; export XDG_VTNR
SSH_AGENT_PID=3132; export SSH_AGENT_PID
XDG_SESSION_ID=2; export XDG_SESSION_ID
HOSTNAME=localhost.localdomain; export HOSTNAME
IMSETTINGS_INTEGRATE_DESKTOP=yes; export IMSETTINGS_INTEGRATE_DESKTOP
GPG_AGENT_INFO=/run/user/1000/keyring-CchymL/gpg:0:1; export GPG_AGENT_INFO
VTE_VERSION=3406; export VTE_VERSION
SHELL=/bin/bash; export SHELL
XDG_MENU_PREFIX=gnome-; export XDG_MENU_PREFIX
HISTSIZE=1000; export HISTSIZE
GJS_DEBUG_OUTPUT=stderr; export GJS_DEBUG_OUTPUT
WINDOWID=25197065; export WINDOWID
GNOME_KEYRING_CONTROL=/run/user/1000/keyring-CchymL; export GNOME_KEYRING_CONTROL
GJS_DEBUG_TOPICS=JS ERROR;JS LOG; export GJS_DEBUG_TOPICS
IMSETTINGS_MODULE=IBus; export IMSETTINGS_MODULE
USER=sunjimeng; export USER
LS_COLORS=rs=0:di=38;5;27:ln=38;5;51:mh=44;38;5;15:pi=40;38;5;11:so=38;5;13:do=38;5;5:bd=48;5;232;38;5;11:cd=48;5;232;38;5;3:or=48;5;232;38;5;9:mi=05;48;5;232;38;5;15:su=48;5;196;38;5;15:sg=48;5;11;38;5;16:ca=48;5;196;38;5;226:tw=48;5;10;38;5;16:ow=48;5;10;38;5;21:st=48;5;21;38;5;15:ex=38;5;34:*.tar=38;5;9:*.tgz=38;5;9:*.arc=38;5;9:*.arj=38;5;9:*.taz=38;5;9:*.lha=38;5;9:*.lz4=38;5;9:*.lzh=38;5;9:*.lzma=38;5;9:*.tlz=38;5;9:*.txz=38;5;9:*.tzo=38;5;9:*.t7z=38;5;9:*.zip=38;5;9:*.z=38;5;9:*.Z=38;5;9:*.dz=38;5;9:*.gz=38;5;9:*.lrz=38;5;9:*.lz=38;5;9:*.lzo=38;5;9:*.xz=38;5;9:*.bz2=38;5;9:*.bz=38;5;9:*.tbz=38;5;9:*.tbz2=38;5;9:*.tz=38;5;9:*.deb=38;5;9:*.rpm=38;5;9:*.jar=38;5;9:*.war=38;5;9:*.ear=38;5;9:*.sar=38;5;9:*.rar=38;5;9:*.alz=38;5;9:*.ace=38;5;9:*.zoo=38;5;9:*.cpio=38;5;9:*.7z=38;5;9:*.rz=38;5;9:*.cab=38;5;9:*.jpg=38;5;13:*.jpeg=38;5;13:*.gif=38;5;13:*.bmp=38;5;13:*.pbm=38;5;13:*.pgm=38;5;13:*.ppm=38;5;13:*.tga=38;5;13:*.xbm=38;5;13:*.xpm=38;5;13:*.tif=38;5;13:*.tiff=38;5;13:*.png=38;5;13:*.svg=38;5;13:*.svgz=38;5;13:*.mng=38;5;13:*.pcx=38;5;13:*.mov=38;5;13:*.mpg=38;5;13:*.mpeg=38;5;13:*.m2v=38;5;13:*.mkv=38;5;13:*.webm=38;5;13:*.ogm=38;5;13:*.mp4=38;5;13:*.m4v=38;5;13:*.mp4v=38;5;13:*.vob=38;5;13:*.qt=38;5;13:*.nuv=38;5;13:*.wmv=38;5;13:*.asf=38;5;13:*.rm=38;5;13:*.rmvb=38;5;13:*.flc=38;5;13:*.avi=38;5;13:*.fli=38;5;13:*.flv=38;5;13:*.gl=38;5;13:*.dl=38;5;13:*.xcf=38;5;13:*.xwd=38;5;13:*.yuv=38;5;13:*.cgm=38;5;13:*.emf=38;5;13:*.axv=38;5;13:*.anx=38;5;13:*.ogv=38;5;13:*.ogx=38;5;13:*.aac=38;5;45:*.au=38;5;45:*.flac=38;5;45:*.mid=38;5;45:*.midi=38;5;45:*.mka=38;5;45:*.mp3=38;5;45:*.mpc=38;5;45:*.ogg=38;5;45:*.ra=38;5;45:*.wav=38;5;45:*.axa=38;5;45:*.oga=38;5;45:*.spx=38;5;45:*.xspf=38;5;45:; export LS_COLORS
SSH_AUTH_SOCK=/run/user/1000/keyring-CchymL/ssh; export SSH_AUTH_SOCK
SESSION_MANAGER=local/unix:@/tmp/.ICE-unix/2990,unix/unix:/tmp/.ICE-unix/2990; export SESSION_MANAGER
USERNAME=sunjimeng; export USERNAME
GNOME_SHELL_SESSION_MODE=classic; export GNOME_SHELL_SESSION_MODE
PATH=/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:/home/sunjimeng/.local/bin:/home/sunjimeng/bin; export PATH
MAIL=/var/spool/mail/sunjimeng; export MAIL
DESKTOP_SESSION=gnome-classic; export DESKTOP_SESSION
QT_IM_MODULE=ibus; export QT_IM_MODULE
PWD=/home/sunjimeng; export PWD
XMODIFIERS=@im=ibus; export XMODIFIERS
GNOME_KEYRING_PID=2967; export GNOME_KEYRING_PID
LANG=zh_CN.utf8; export LANG
GDM_LANG=zh_CN.utf8; export GDM_LANG
GDMSESSION=gnome-classic; export GDMSESSION
HISTCONTROL=ignoredups; export HISTCONTROL
XDG_SEAT=seat0; export XDG_SEAT
HOME=/home/sunjimeng; export HOME
SHLVL=2; export SHLVL
GNOME_DESKTOP_SESSION_ID=this-is-deprecated; export GNOME_DESKTOP_SESSION_ID
LOGNAME=sunjimeng; export LOGNAME
DBUS_SESSION_BUS_ADDRESS=unix:abstract=/tmp/dbus-O0naLUCbYg,guid=ad8d9a1bab9eccd8c11d0a6257493a83; export DBUS_SESSION_BUS_ADDRESS
LESSOPEN=||/usr/bin/lesspipe.sh %s; export LESSOPEN
WINDOWPATH=1; export WINDOWPATH
XDG_RUNTIME_DIR=/run/user/1000; export XDG_RUNTIME_DIR
COLORTERM=gnome-terminal; export COLORTERM
XAUTHORITY=/run/gdm/auth-for-sunjimeng-Bcg9Bg/database; export XAUTHORITY
cd /home/sunjimeng || {
     echo 'Execution directory inaccessible' >&2
     exit 1
}
${SHELL:-/bin/sh} << 'marcinDELIMITER7e20521d'
ls -l

marcinDELIMITER7e20521d
[sunjimeng@localhost ~]$ 

      7)[sunjimeng@localhost ~]$ at -d 21　　　　　　　　取消指向执行id号为21的任务

[sunjimeng@localhost ~]$ atq
20    Wed Jun  8 18:15:00 2016 a sunjimeng
21    Wed Jun  8 18:16:00 2016 a sunjimeng
[sunjimeng@localhost ~]$ atrm 20
[sunjimeng@localhost ~]$ atq
21    Wed Jun  8 18:16:00 2016 a sunjimeng
[sunjimeng@localhost ~]$ at -d 21
[sunjimeng@localhost ~]$ atq