timeout 是個奇妙的Linux命令，它可以控制程序運行的時間，這對于我們希望控制程序的運行時間非常有用。
timeout在CentOS 6平臺上，從屬于軟件包coreutils
# which timeout
/usr/bin/timeout
# rpm -qf /usr/bin/timeout
coreutils-8.4-19.el6_4.2.x86_64
timeout的原理很簡單，一個簡單的計時器，一個kill命令，其中-s 可以跟kill的參數，具體怎么殺，就看它。
man timeout僅僅半頁，如下
TIMEOUT(1) User Commands TIMEOUT(1)
NAME
timeout - run a commandwith a timelimit
SYNOPSIS
timeout [OPTION] NUMBER[SUFFIX] COMMAND [ARG]...
timeout [OPTION]
DESCRIPTION
Start COMMAND, and killit ifstill running after NUMBER seconds. SUFFIX may be ‘s’forseconds (the default), ‘m’ forminutes, ‘h’
forhours or ‘d’ fordays.
Mandatory arguments to long options are mandatory forshort options too.
-s, --signal=SIGNAL
specify the signal to be sent on timeout. SIGNAL may be a name like ‘HUP’ or a number. See ‘kill-l‘ fora list of signals
--help display this help and exit
--version
output version information and exit
If the commandtimesout, thenexitwith status 124. Otherwise, exitwith the status of COMMAND. If no signal is specified, send the
TERM signal upon timeout. The TERM signal kills any process that does not block or catch that signal. For other processes, it may be
necessary to use the KILL (9) signal, since this signal cannot be caught.
AUTHOR
Written by Padraig Brady.
用法舉例
1timeout 120 command
上面的command命令如果在120秒內完成，則平安結束，運行超過120秒后將被殺死。
腳本經常是傻乎乎的一口氣跑到完，搞得我們需要寫另一個腳本定期去殺它。自打有了timeout命令，腰也不疼了，腿也不酸了，跑跑歇歇更健康。
一句話，我們在腳本里或者crontab里就不用再造輪子了。
