[[PageOutline]]

 * [http://miya0.dyndns.org/pc/settei/crontab.html crontabの書き方]
 * [http://www.server-memo.net/tips/crontab.html crontabの書き方 — server-memo.net]

 = 遅延実行 =
 * [http://d.hatena.ne.jp/Oswald/20090117/1232175381 cronスクリプトをバックグラウンドで実行するときの注意点 - ハッカー現役続行]
   * これを解決するには、このプロセスがopenしているファイルディスクリプタをcloseします。
{{{
sleep 15 >/dev/null 2>&1 &
}}}

 == 問題 ==
 * 次のようなタスクを登録した場合
   1. /etc/cron.hourly/1
{{{
#!/bin/sh

sleep 60
touch /tmp/1.$$.`date +%T.%N`
ls -l /tmp/1*
}}}
   1. /etc/cron.hourly/2
{{{
#!/bin/sh

sleep 60
touch /tmp/2.$$.`date +%T.%N`
ls -l /tmp/2*
}}}
   1. /etc/cron.hourly/3
{{{
#!/bin/sh

sleep 60
touch /tmp/3.$$.`date +%T.%N`
ls -l /tmp/3*
}}}

 * 1 -> 2 -> 3 と逐次実行されるため、同時並行より遅いタイミングでタスクが処理される
   1. pstree -ap
{{{
  ├─cron,3751
  │   └─cron,3792
  │       └─sh,3794 -c    cd / && run-parts --report /etc/cron.hourly
  │           └─run-parts,3795 --report /etc/cron.hourly
  │               └─1,3796 /etc/cron.hourly/1
  │                  └─sleep,3797 60
}}}
   1. pstree -ap
{{{
  ├─cron,3751
  │   └─cron,3792
  │       ├─sendmail,3806 -i -FCronDaemon -oem root
  │       │   └─postdrop,3809 -r
  │       └─sh,3794 -c    cd / && run-parts --report /etc/cron.hourly
  │           └─run-parts,3795 --report /etc/cron.hourly
  │               └─2,3807 /etc/cron.hourly/2
  │                  └─sleep,3808 60
}}}
   1. pstree -ap
{{{
  ├─cron,3751
  │   └─cron,3792
  │       ├─sendmail,3806 -i -FCronDaemon -oem root
  │       │   └─postdrop,3809 -r
  │       └─sh,3794 -c    cd / && run-parts --report /etc/cron.hourly
  │           └─run-parts,3795 --report /etc/cron.hourly
  │               └─3,3816 /etc/cron.hourly/3
  │                  └─sleep,3817 60
}}}

 * 実行ログはまとめて配送される
   * mail
{{{
Mail version 8.1.2 01/15/2001.  Type ? for help.
"/var/mail/mitty": 1 message 1 new
>N  1 root@lucid.mitty.  Tue May 18 17:20   24/968   Cron <root@lucid>    cd / &
&
Message 1:
From root@lucid.mitty.jp  Tue May 18 17:20:01 2010
X-Original-To: root
From: root@lucid.mitty.jp (Cron Daemon)
To: root@lucid.mitty.jp
Subject: Cron <root@lucid>    cd / && run-parts --report /etc/cron.hourly
Content-Type: text/plain; charset=ANSI_X3.4-1968
X-Cron-Env: <SHELL=/bin/sh>
X-Cron-Env: <PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin>
X-Cron-Env: <HOME=/root>
X-Cron-Env: <LOGNAME=root>
Date: Tue, 18 May 2010 17:18:01 +0900 (JST)

/etc/cron.hourly/1:
-rw-r--r-- 1 root root 0 May 18 17:18 /tmp/1.3796.17:18:01.530794512
/etc/cron.hourly/2:
-rw-r--r-- 1 root root 0 May 18 17:19 /tmp/2.3807.17:19:01.552276713
/etc/cron.hourly/3:
-rw-r--r-- 1 root root 0 May 18 17:20 /tmp/3.3816.17:20:01.573785281
}}}

 === サブシェルにより解決法 ===
 * 各タスクを次のようにサブシェル化する
   1. /etc/cron.hourly/1
{{{
#!/bin/sh

(
sleep 60
touch /tmp/1.$$.`date +%T.%N`
ls -l /tmp/1* 2>&1 | mail $LOGNAME
) >/dev/null 2>&1 &
}}}
   1. /etc/cron.hourly/2
{{{
#!/bin/sh

(
sleep 60
touch /tmp/2.$$.`date +%T.%N`
ls -l /tmp/2* 2>&1 | mail $LOGNAME
) >/dev/null 2>&1 &
}}}
   1. /etc/cron.hourly/3
{{{
#!/bin/sh

(
sleep 60
touch /tmp/3.$$.`date +%T.%N`
ls -l /tmp/3* 2>&1 | mail $LOGNAME
) >/dev/null 2>&1 &
}}}

 * 同時実行される
   *  pstree -ap
{{{
  ├─1,3860 /etc/cron.hourly/1
  │  └─sleep,3865 60
  ├─2,3862 /etc/cron.hourly/2
  │  └─sleep,3864 60
  ├─3,3866 /etc/cron.hourly/3
  │  └─sleep,3867 60

  ├─cron,3836
}}}

 * 実行ログはmailコマンドにより個別に配送される
   * mail
{{{
Mail version 8.1.2 01/15/2001.  Type ? for help.
"/var/mail/mitty": 3 messages 3 new
>N  1 root@lucid.mitty.  Tue May 18 17:18   13/480
 N  2 root@lucid.mitty.  Tue May 18 17:18   13/480
 N  3 root@lucid.mitty.  Tue May 18 17:18   13/480
&
Message 1:
From root@lucid.mitty.jp  Tue May 18 17:18:01 2010
X-Original-To: root
To: root@lucid.mitty.jp
Date: Tue, 18 May 2010 17:18:01 +0900 (JST)
From: root@lucid.mitty.jp (root)

-rw-r--r-- 1 root root 0 May 18 17:18 /tmp/3.3863.17:18:01.400271817

&
Message 2:
From root@lucid.mitty.jp  Tue May 18 17:18:01 2010
X-Original-To: root
To: root@lucid.mitty.jp
Date: Tue, 18 May 2010 17:18:01 +0900 (JST)
From: root@lucid.mitty.jp (root)

-rw-r--r-- 1 root root 0 May 18 17:18 /tmp/2.3861.17:18:01.397221662

&
Message 3:
From root@lucid.mitty.jp  Tue May 18 17:18:01 2010
X-Original-To: root
To: root@lucid.mitty.jp
Date: Tue, 18 May 2010 17:18:01 +0900 (JST)
From: root@lucid.mitty.jp (root)

-rw-r--r-- 1 root root 0 May 18 17:18 /tmp/1.3859.17:18:01.401215856
}}}

 == 実行サンプル ==
 * /etc/cron.hourly/crontest
{{{
#!/bin/sh

(
/bin/df -h 2>&1 | mail -E -s "Cron <$LOGNAME@`/bin/hostname`> $0" $LOGNAME
) >/dev/null 2>&1 &
}}}
 * mail
{{{
Mail version 8.1.2 01/15/2001.  Type ? for help.
"/var/mail/mitty": 1 message 1 new
>N  1 root@lucid.mitty.  Wed May 19 10:17   21/903   Cron <root@lucid> /etc/cron
&
Message 1:
From root@lucid.mitty.jp  Wed May 19 10:17:01 2010
X-Original-To: root
To: root@lucid.mitty.jp
Subject: Cron <root@lucid> /etc/cron.hourly/crontest
Date: Wed, 19 May 2010 10:17:01 +0900 (JST)
From: root@lucid.mitty.jp (root)

Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1             3.8G  903M  2.9G  24% /
none                  243M  168K  243M   1% /dev
none                  247M     0  247M   0% /dev/shm
none                  247M   40K  247M   1% /var/run
none                  247M     0  247M   0% /var/lock
none                  247M     0  247M   0% /lib/init/rw
none                  3.8G  903M  2.9G  24% /var/lib/ureadahead/debugfs
}}}

 = 遅延実行テスト =
 * crontab -l
{{{
*/2 * * * * /home/mitty/crontest
}}}

 == フォアグラウンド sleep ==
 * /home/mitty/crontest
{{{
#!/bin/sh

export LANG=C


touch /tmp/$$.`date +%T`
ls -l /tmp

sleep 60;

touch /tmp/$$.`date +%T`
ls -l /tmp
}}}

 * pstree -ap
{{{
  ├─cron,662
  │   └─cron,2325
  │       ├─sendmail,2332 -i -FCronDaemon -oem mitty
  │       │   └─postdrop,2333 -r
  │       └─sh,2326 -c /home/mitty/crontest
  │           └─crontest,2327 /home/mitty/crontest
  │               └─sleep,2331 60
}}}

 * mail
{{{
Mail version 8.1.2 01/15/2001.  Type ? for help.
"/var/mail/mitty": 1 message 1 new
>N  1 root@lucid.mitty.  Tue May 18 16:07   25/937   Cron <mitty@lucid> /home/mi
&
Message 1:
From mitty@lucid.mitty.jp  Tue May 18 16:07:01 2010
X-Original-To: mitty
From: root@lucid.mitty.jp (Cron Daemon)
To: mitty@lucid.mitty.jp
Subject: Cron <mitty@lucid> /home/mitty/crontest
Content-Type: text/plain; charset=ANSI_X3.4-1968
X-Cron-Env: <SHELL=/bin/sh>
X-Cron-Env: <HOME=/home/mitty>
X-Cron-Env: <PATH=/usr/bin:/bin>
X-Cron-Env: <LOGNAME=mitty>
Date: Tue, 18 May 2010 16:06:01 +0900 (JST)

total 0
-rw-r--r-- 1 mitty mitty  0 May 18 16:06 2327.16:06:01
drwx------ 2 mitty mitty 22 May 18 13:51 ssh-qAiiolp854
total 0
-rw-r--r-- 1 mitty mitty  0 May 18 16:06 2327.16:06:01
-rw-r--r-- 1 mitty mitty  0 May 18 16:07 2327.16:07:01
drwx------ 2 mitty mitty 22 May 18 13:51 ssh-qAiiolp854
}}}

 === with mail command ===
 * /home/mitty/crontest
{{{
#!/bin/sh

export LANG=C


touch /tmp/$$.`date +%T`
ls -l /tmp 2>&1 | mail $LOGNAME

sleep 60;

touch /tmp/$$.`date +%T`
ls -l /tmp 2>&1 | mail $LOGNAME
}}}

 * pstree -ap
{{{
  ├─cron,662
  │   └─cron,2647
  │       └─sh,2649 -c /home/mitty/crontest
  │           └─crontest,2650 /home/mitty/crontest
  │               └─sleep,2658 60
}}}

 * mail
{{{
Mail version 8.1.2 01/15/2001.  Type ? for help.
"/var/mail/mitty": 2 messages 2 new
>N  1 mitty@lucid.mitty  Tue May 18 16:30   15/540
 N  2 mitty@lucid.mitty  Tue May 18 16:31   16/595
&
Message 1:
From mitty@lucid.mitty.jp  Tue May 18 16:30:01 2010
X-Original-To: mitty
To: mitty@lucid.mitty.jp
Date: Tue, 18 May 2010 16:30:01 +0900 (JST)
From: mitty@lucid.mitty.jp (mitty)

total 0
-rw-r--r-- 1 mitty mitty  0 May 18 16:30 2650.16:30:01
drwx------ 2 mitty mitty 22 May 18 13:51 ssh-qAiiolp854

&
Message 2:
From mitty@lucid.mitty.jp  Tue May 18 16:31:02 2010
X-Original-To: mitty
To: mitty@lucid.mitty.jp
Date: Tue, 18 May 2010 16:31:01 +0900 (JST)
From: mitty@lucid.mitty.jp (mitty)

total 0
-rw-r--r-- 1 mitty mitty  0 May 18 16:30 2650.16:30:01
-rw-r--r-- 1 mitty mitty  0 May 18 16:31 2650.16:31:01
drwx------ 2 mitty mitty 22 May 18 13:51 ssh-qAiiolp854
}}}



 == バックグラウンド sleep ==
 * /home/mitty/crontest
{{{
#!/bin/sh

export LANG=C


touch /tmp/cron.$$.`date +%T.%N`
ls -l /tmp

sleep 60 &

touch /tmp/cron.$$.`date +%T.%N`
ls -l /tmp
}}}

 * pstree -ap
{{{
  ├─cron,662
  │   └─cron,2948
  │       ├─sendmail,2955 -i -FCronDaemon -oem mitty
  │       │   └─postdrop,2959 -r
  │       └─(sh,2950)

  ├─sleep,2956 60
}}}

 * mail
{{{
Mail version 8.1.2 01/15/2001.  Type ? for help.
"/var/mail/mitty": 1 message 1 new
>N  1 root@lucid.mitty.  Tue May 18 16:53   25/982   Cron <mitty@lucid> /home/mi
&
Message 1:
From mitty@lucid.mitty.jp  Tue May 18 16:53:02 2010
X-Original-To: mitty
From: root@lucid.mitty.jp (Cron Daemon)
To: mitty@lucid.mitty.jp
Subject: Cron <mitty@lucid> /home/mitty/crontest
Content-Type: text/plain; charset=ANSI_X3.4-1968
X-Cron-Env: <SHELL=/bin/sh>
X-Cron-Env: <HOME=/home/mitty>
X-Cron-Env: <PATH=/usr/bin:/bin>
X-Cron-Env: <LOGNAME=mitty>
Date: Tue, 18 May 2010 16:52:02 +0900 (JST)

total 0
-rw-r--r-- 1 mitty mitty  0 May 18 16:52 cron.2951.16:52:01.997709994
drwx------ 2 mitty mitty 22 May 18 13:51 ssh-qAiiolp854
total 0
-rw-r--r-- 1 mitty mitty  0 May 18 16:52 cron.2951.16:52:01.997709994
-rw-r--r-- 1 mitty mitty  0 May 18 16:52 cron.2951.16:52:02.013689211
drwx------ 2 mitty mitty 22 May 18 13:51 ssh-qAiiolp854
}}}

 === with mail command ===
 * /home/mitty/crontest
{{{
#!/bin/sh

export LANG=C


touch /tmp/cron.$$.`date +%T.%N`
ls -l /tmp 2>&1 | mail $LOGNAME

sleep 60 &

touch /tmp/cron.$$.`date +%T.%N`
ls -l /tmp 2>&1 | mail $LOGNAME
}}}

 * pstree -ap
{{{
  ├─cron,662
  │   └─cron,3006
  │       └─(sh,3008)

  ├─sleep,3017 60
}}}

 * mail
{{{
Mail version 8.1.2 01/15/2001.  Type ? for help.
"/var/mail/mitty": 2 messages 2 new
>N  1 mitty@lucid.mitty  Tue May 18 16:56   15/555
 N  2 mitty@lucid.mitty  Tue May 18 16:56   16/625
&
Message 1:
From mitty@lucid.mitty.jp  Tue May 18 16:56:01 2010
X-Original-To: mitty
To: mitty@lucid.mitty.jp
Date: Tue, 18 May 2010 16:56:01 +0900 (JST)
From: mitty@lucid.mitty.jp (mitty)

total 0
-rw-r--r-- 1 mitty mitty  0 May 18 16:56 cron.3009.16:56:01.044354156
drwx------ 2 mitty mitty 22 May 18 13:51 ssh-qAiiolp854

&
Message 2:
From mitty@lucid.mitty.jp  Tue May 18 16:56:01 2010
X-Original-To: mitty
To: mitty@lucid.mitty.jp
Date: Tue, 18 May 2010 16:56:01 +0900 (JST)
From: mitty@lucid.mitty.jp (mitty)

total 0
-rw-r--r-- 1 mitty mitty  0 May 18 16:56 cron.3009.16:56:01.044354156
-rw-r--r-- 1 mitty mitty  0 May 18 16:56 cron.3009.16:56:01.089449007
drwx------ 2 mitty mitty 22 May 18 13:51 ssh-qAiiolp854
}}}

 === >/dev/null 2>&1 & ===
 * /home/mitty/crontest
{{{
#!/bin/sh

export LANG=C


touch /tmp/cron.$$.`date +%T.%N`
ls -l /tmp 2>&1 | mail $LOGNAME

sleep 60 >/dev/null 2>&1 &

touch /tmp/cron.$$.`date +%T.%N`
ls -l /tmp 2>&1 | mail $LOGNAME
}}}

 * pstree -ap
{{{
  ├─cron,662

  ├─sleep,3083 60
}}}

 * mail
{{{
Mail version 8.1.2 01/15/2001.  Type ? for help.
"/var/mail/mitty": 2 messages 2 new
>N  1 mitty@lucid.mitty  Tue May 18 17:00   15/555
 N  2 mitty@lucid.mitty  Tue May 18 17:00   16/625
&
Message 1:
From mitty@lucid.mitty.jp  Tue May 18 17:00:01 2010
X-Original-To: mitty
To: mitty@lucid.mitty.jp
Date: Tue, 18 May 2010 17:00:01 +0900 (JST)
From: mitty@lucid.mitty.jp (mitty)

total 0
-rw-r--r-- 1 mitty mitty  0 May 18 17:00 cron.3075.17:00:01.108414369
drwx------ 2 mitty mitty 22 May 18 13:51 ssh-qAiiolp854

&
Message 2:
From mitty@lucid.mitty.jp  Tue May 18 17:00:01 2010
X-Original-To: mitty
To: mitty@lucid.mitty.jp
Date: Tue, 18 May 2010 17:00:01 +0900 (JST)
From: mitty@lucid.mitty.jp (mitty)

total 0
-rw-r--r-- 1 mitty mitty  0 May 18 17:00 cron.3075.17:00:01.108414369
-rw-r--r-- 1 mitty mitty  0 May 18 17:00 cron.3075.17:00:01.161439061
drwx------ 2 mitty mitty 22 May 18 13:51 ssh-qAiiolp854
}}}

 == サブシェル ==
 * /home/mitty/crontest 
{{{
#!/bin/sh

export LANG=C

(

touch /tmp/cron.$$.`date +%T.%N`
ls -l /tmp 2>&1 | mail $LOGNAME

sleep 60

touch /tmp/cron.$$.`date +%T.%N`
ls -l /tmp 2>&1 | mail $LOGNAME

)  >/dev/null 2>&1 &
}}}

 * pstree -ap
{{{
  ├─cron,662
  ├─crontest,3343 /home/mitty/crontest
  │   └─sleep,3351 60
}}}

 * mail
{{{
Mail version 8.1.2 01/15/2001.  Type ? for help.
"/var/mail/mitty": 2 messages 2 new
>N  1 mitty@lucid.mitty  Tue May 18 17:24   15/555
 N  2 mitty@lucid.mitty  Tue May 18 17:25   16/625
&
Message 1:
From mitty@lucid.mitty.jp  Tue May 18 17:24:01 2010
X-Original-To: mitty
To: mitty@lucid.mitty.jp
Date: Tue, 18 May 2010 17:24:01 +0900 (JST)
From: mitty@lucid.mitty.jp (mitty)

total 0
-rw-r--r-- 1 mitty mitty  0 May 18 17:24 cron.3342.17:24:01.565319416
drwx------ 2 mitty mitty 22 May 18 13:51 ssh-qAiiolp854

&
Message 2:
From mitty@lucid.mitty.jp  Tue May 18 17:25:01 2010
X-Original-To: mitty
To: mitty@lucid.mitty.jp
Date: Tue, 18 May 2010 17:25:01 +0900 (JST)
From: mitty@lucid.mitty.jp (mitty)

total 0
-rw-r--r-- 1 mitty mitty  0 May 18 17:24 cron.3342.17:24:01.565319416
-rw-r--r-- 1 mitty mitty  0 May 18 17:25 cron.3342.17:25:01.614828392
drwx------ 2 mitty mitty 22 May 18 13:51 ssh-qAiiolp854
}}}

 = 環境変数 =
 == Ubuntu lucid ==
 === normal user task ===
 * crontab -l
{{{
* * * * * /home/mitty/test
}}}
 * cat /home/mitty/test
{{{
#!/bin/sh

export
}}}
 * mail
{{{
From mitty@lucid.mitty.jp  Tue May 18 16:25:01 2010
X-Original-To: mitty
From: root@lucid.mitty.jp (Cron Daemon)
To: mitty@lucid.mitty.jp
Subject: Cron <mitty@lucid> /home/mitty/test
Content-Type: text/plain; charset=ANSI_X3.4-1968
X-Cron-Env: <SHELL=/bin/sh>
X-Cron-Env: <HOME=/home/mitty>
X-Cron-Env: <PATH=/usr/bin:/bin>
X-Cron-Env: <LOGNAME=mitty>
Date: Tue, 18 May 2010 16:25:01 +0900 (JST)

export HOME='/home/mitty'
export LOGNAME='mitty'
export PATH='/usr/bin:/bin'
export PWD='/home/mitty'
export SHELL='/bin/sh'
}}}
 === system task ===
 * cat /etc/cron.hourly/test
{{{
#!/bin/sh

export
}}}
 * mail
{{{
From root@lucid.mitty.jp  Tue May 18 17:17:01 2010
X-Original-To: root
From: root@lucid.mitty.jp (Cron Daemon)
To: root@lucid.mitty.jp
Subject: Cron <root@lucid>    cd / && run-parts --report /etc/cron.hourly
Content-Type: text/plain; charset=ANSI_X3.4-1968
X-Cron-Env: <SHELL=/bin/sh>
X-Cron-Env: <PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin>
X-Cron-Env: <HOME=/root>
X-Cron-Env: <LOGNAME=root>
Date: Tue, 18 May 2010 17:17:01 +0900 (JST)

/etc/cron.hourly/test:
export HOME='/root'
export LOGNAME='root'
export OLDPWD='/root'
export PATH='/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin'
export PWD='/'
export SHELL='/bin/sh'
}}}