blocks|key|1058232|text|您可以使用shell循环模拟基本功能：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1058233|while+:;+do+clear;+your_command;+sleep+2;+done|code-block|syntax|javascript|1058234|这将永远循环，清除屏幕，运行您的命令，并等待两秒钟-基本的watch+your_command实现。|offset|length|style|CODE|1058235|您可以更进一步，创建一个可以接受your_command和sleep_duration作为参数的watch.sh脚本：|1058236|#!/bin/bash
#+usage:+watch.sh+<your_command>+<sleep_duration>

while+:;+
++do+
++clear
++date
++$1
++sleep+$2
done|1058237|entityMap^0|0|0|T|I|0|G|C|T|E|1C|8|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@$I|V|J|W|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|X|8|@$I|Y|J|Z|K|L]|$I|10|J|11|K|L]|$I|12|J|13|K|L]]|9|@]|A|$]]|$1|O|3|P|5|D|7|14|8|@]|9|@]|A|$E|F]]|$1|Q|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|R|$]]

You can emulate the basic functionality with the shell loop:

<pre><code>while :; do clear; your_command; sleep 2; done
</code></pre>

That will loop forever, clear the screen, run your command, and wait two seconds - the basic <code>watch your_command</code> implementation.

You can take this a step further and create a <code>watch.sh</code> script that can accept <code>your_command</code> and <code>sleep_duration</code> as parameters:

<pre><code>#!/bin/bash
# usage: watch.sh &lt;your_command&gt; &lt;sleep_duration&gt;

while :; 
 do 
 clear
 date
 $1
 sleep $2
done
</code></pre>

blocks|key|760452|text|我将采用here的答案|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|760453|bash+-c+'while+[+0+];+do+<your+command>;+sleep+5;+done'|code-block|syntax|javascript|760454|但你最好还是用installing+watch，因为这不是很干净...|760455|entityMap|0|LINK|mutability|MUTABLE|url|https://unix.stackexchange.com/questions/10646/repeat-a-unix-command-every-x-seconds-forever/28859#28859|1|http://osxdaily.com/2010/08/22/install-watch-command-on-os-x/^0|4|4|0|0|0|7|G|1|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@$A|V|B|W|1|X]]|C|$]]|$1|D|3|E|5|F|7|Y|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|Z|8|@]|9|@$A|10|B|11|1|12]]|C|$]]|$1|K|3|-4|5|6|7|13|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]|S|$5|N|O|P|C|$Q|T]]]]

I am going with the answer from <a href="https://unix.stackexchange.com/questions/10646/repeat-a-unix-command-every-x-seconds-forever/28859#28859">here</a>:
<pre><code>bash -c 'while [ 0 ]; do &lt;your command&gt;; sleep 5; done'
</code></pre>
But you're really better off <a href="http://osxdaily.com/2010/08/22/install-watch-command-on-os-x/" rel="nofollow noreferrer">installing watch</a> as this isn't very clean...

blocks|key|1775736|text|也许“看”不是你想要的。您可能希望寻求帮助来解决您的问题，而不是实现您的解决方案！:)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1775737|如果您的真正目标是基于从tail命令中看到的内容来触发操作，那么您可以将其作为尾部本身的一部分来实现。您可以按需运行代码，而不是像watch那样“定期”运行。|offset|length|style|CODE|1775738|#!/bin/sh

tail+-F+/var/log/somelogfile+%7C+while+read+line;+do
++if+echo+"$line"+%7C+grep+-q+'[Ss]ome.regex';+then
++++#+do+your+stuff
++fi
done|code-block|syntax|javascript|1775739|请注意，tail+-F将继续跟踪日志文件，即使它被newsyslog或logrotate轮换。您希望使用它而不是小写的tail+-f。有关详细信息，请查看man+tail。|1775740|也就是说，如果您确实希望定期运行命令，可以将提供的其他答案转换为简短的shell脚本：|1775741|#!/bin/sh
if+[+-z+"$2"+];+then
++echo+"Usage:+$0+SECONDS+COMMAND"+>&2
++exit+1
fi

SECONDS=$1
shift+1
while+sleep+$SECONDS;+do
++clear
++$*
done|1775742|entityMap^0|0|C|4|1T|5|0|0|4|7|1N|7|25|8|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@$D|W|E|X|F|G]|$D|Y|E|Z|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|10|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|11|8|@$D|12|E|13|F|G]|$D|14|E|15|F|G]|$D|16|E|17|F|G]]|9|@]|A|$]]|$1|O|3|P|5|6|7|18|8|@]|9|@]|A|$]]|$1|Q|3|R|5|J|7|19|8|@]|9|@]|A|$K|L]]|$1|S|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]]|T|$]]

It may be that "watch" is not what you want. You probably want to ask for help in solving your problem, not in implementing your solution! :)

If your real goal is to trigger actions based on what's seen from the <code>tail</code> command, then you can do that as part of the tail itself. Instead of running "periodically", which is what <code>watch</code> does, you can run your code on demand.

<pre><code>#!/bin/sh

tail -F /var/log/somelogfile | while read line; do
 if echo "$line" | grep -q '[Ss]ome.regex'; then
 # do your stuff
 fi
done
</code></pre>

Note that <code>tail -F</code> will continue to follow a log file even if it gets rotated by newsyslog or logrotate. You want to use this instead of the lower-case <code>tail -f</code>. Check <code>man tail</code> for details.

That said, if you really do want to run a command periodically, the other answers provided can be turned into a short shell script:

<pre><code>#!/bin/sh
if [ -z "$2" ]; then
 echo "Usage: $0 SECONDS COMMAND" &gt;&amp;2
 exit 1
fi

SECONDS=$1
shift 1
while sleep $SECONDS; do
 clear
 $*
done
</code></pre>

blocks|key|760455|text|上面的shell可以做到这一点，您甚至可以将它们转换为别名(您可能需要包装在一个函数中来处理参数)：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|760456|alias+myWatch='_()+{+while+:;+do+clear;+$2;+sleep+$1;+done+};+_'|code-block|syntax|javascript|760457|示例：|760458|myWatch+1+ls+##+Self-explanatory
myWatch+5+"ls+-lF+$HOME"+##+Every+5+seconds,+list+out+home+directory;+double-quotes+around+command+to+keep+its+arguments+together|760459|或者，Homebrew可以从http://procps.sourceforge.net/安装手表|offset|length|760460|brew+install+watch|760461|entityMap|0|LINK|mutability|MUTABLE|url|https://en.wikipedia.org/wiki/Homebrew_%2528package_management_software%2529|1|http://procps.sourceforge.net/^0|0|0|0|0|3|8|0|E|U|1|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|12|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|13|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|14|8|@]|9|@$M|15|N|16|1|17]|$M|18|N|19|1|1A]]|A|$]]|$1|O|3|P|5|D|7|1B|8|@]|9|@]|A|$E|F]]|$1|Q|3|-4|5|6|7|1C|8|@]|9|@]|A|$]]]|R|$S|$5|T|U|V|A|$W|X]]|Y|$5|T|U|V|A|$W|Z]]]]

The shells above will do the trick, and you could even convert them to an alias (you may need to wrap in a function to handle parameters):
<pre><code>alias myWatch='_() { while :; do clear; $2; sleep $1; done }; _'
</code></pre>
Examples:
<pre><code>myWatch 1 ls ## Self-explanatory
myWatch 5 &quot;ls -lF $HOME&quot; ## Every 5 seconds, list out home directory; double-quotes around command to keep its arguments together
</code></pre>
Alternately, <a href="https://en.wikipedia.org/wiki/Homebrew_%28package_management_software%29" rel="nofollow noreferrer">Homebrew</a> can install the watch from <a href="http://procps.sourceforge.net/" rel="nofollow noreferrer">http://procps.sourceforge.net/</a>:
<pre><code>brew install watch
</code></pre>

blocks|key|1775752|text|使用MacPorts|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1775753|$+sudo+port+install+watch|code-block|syntax|javascript|1775754|entityMap|0|LINK|mutability|MUTABLE|url|http://www.macports.org/^0|2|8|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

Use <a href="http://www.macports.org/" rel="nofollow noreferrer">MacPorts</a>:
<pre><code>$ sudo port install watch
</code></pre>

blocks|key|5096197|text|或者，在~/.bashrc文件中：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5096198|function+watch+{
++++while+:;+do+clear;+date;+echo;+$@;+sleep+2;+done
}|code-block|syntax|javascript|5096199|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Or, in your ~/.bashrc file:
<pre><code>function watch {
 while :; do clear; date; echo; $@; sleep 2; done
}
</code></pre>

blocks|key|5096225|text|安装了Homebrew后：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|5096226|brew+install+watch|style|CODE|5096227|entityMap|0|LINK|mutability|MUTABLE|url|http://brew.sh/^0|3|8|0|0|0|I|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@$A|Q|B|R|1|S]]|C|$]]|$1|D|3|E|5|6|7|T|8|@$A|U|B|V|F|G]]|9|@]|C|$]]|$1|H|3|-4|5|6|7|W|8|@]|9|@]|C|$]]]|I|$J|$5|K|L|M|C|$N|O]]]]

With <a href="http://brew.sh/">Homebrew</a> installed:

<code>brew install watch</code>

blocks|key|760543|text|下面是一个略微更改过的of+this+answer版本：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|760544|760545|检查有效参数|unordered-list-item|760546|在顶部显示日期和持续时间标题|760547|将"+duration“参数移动为第一个参数，因此可以轻松地将复杂命令作为其余参数进行传递。|760548|760549|要使用它：|760550|760551|通过运行watch+1+echo+"hi+there"|style|CODE|760552|将其保存到终端中的chmod+700+~/bin/watch，使其对其执行executable.|760553|try操作|760554|760555|~/bin/观看|BOLD|760556|#!/bin/bash

function+show_help()
{
++echo+""
++echo+"usage:+watch+[sleep+duration+in+seconds]+[command]"
++echo+""
++echo+"e.g.+To+cat+a+file+every+second,+run+the+following"
++echo+""
++echo+"+++++watch+1+cat+/tmp/it.txt"+
++exit;
}

function+show_help_if_required()
{
++if+[+"$1"+==+"help"+]
++then
++++++show_help
++fi
++if+[+-z+"$1"+]
++++then
++++++show_help
++fi
}

function+require_numeric_value()
{
++REG_EX='%5E[0-9]%2B$'
++if+!+[[+$1+=~+$REG_EX+]]+;+then
++++show_help
++fi
}

show_help_if_required+$1
require_numeric_value+$1

DURATION=$1
shift

while+:;+do+
++clear
++echo+"Updating+every+$DURATION+seconds.+Last+updated+$(date)"
++bash+-c+"$*"
++sleep+$DURATION
done|code-block|syntax|javascript|760557|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/9574089/osx-bash-watch-command/9574123#9574123^0|B|E|0|0|0|0|0|0|0|0|0|4|N|0|9|L|0|0|0|0|8|0|0^^$0|@$1|2|3|4|5|6|7|1E|8|@]|9|@$A|1F|B|1G|1|1H]]|C|$]]|$1|D|3|-4|5|6|7|1I|8|@]|9|@]|C|$]]|$1|E|3|F|5|G|7|1J|8|@]|9|@]|C|$]]|$1|H|3|I|5|G|7|1K|8|@]|9|@]|C|$]]|$1|J|3|K|5|G|7|1L|8|@]|9|@]|C|$]]|$1|L|3|-4|5|6|7|1M|8|@]|9|@]|C|$]]|$1|M|3|N|5|6|7|1N|8|@]|9|@]|C|$]]|$1|O|3|-4|5|6|7|1O|8|@]|9|@]|C|$]]|$1|P|3|Q|5|G|7|1P|8|@$A|1Q|B|1R|R|S]]|9|@]|C|$]]|$1|T|3|U|5|6|7|1S|8|@$A|1T|B|1U|R|S]]|9|@]|C|$]]|$1|V|3|W|5|G|7|1V|8|@]|9|@]|C|$]]|$1|X|3|-4|5|6|7|1W|8|@]|9|@]|C|$]]|$1|Y|3|Z|5|6|7|1X|8|@$A|1Y|B|1Z|R|10]]|9|@]|C|$]]|$1|11|3|12|5|13|7|20|8|@]|9|@]|C|$14|15]]|$1|16|3|-4|5|6|7|21|8|@]|9|@]|C|$]]]|17|$18|$5|19|1A|1B|C|$1C|1D]]]]

Here's a slightly changed version <a href="https://stackoverflow.com/questions/9574089/osx-bash-watch-command/9574123#9574123">of this answer</a> that:

<ul>
<li>checks for valid args</li>
<li>shows a date and duration title at the top</li>
<li>moves the "duration" argument to be the 1st argument, so complex commands can be easily passed as the remaining arguments.</li>
</ul>

To use it:

<ul>
<li>Save this to <code>~/bin/watch</code></li>
<li>execute <code>chmod 700 ~/bin/watch</code> in a terminal to make it executable.</li>
<li>try it by running <code>watch 1 echo "hi there"</code></li>
</ul>

~/bin/watch

<pre><code>#!/bin/bash

function show_help()
{
 echo ""
 echo "usage: watch [sleep duration in seconds] [command]"
 echo ""
 echo "e.g. To cat a file every second, run the following"
 echo ""
 echo " watch 1 cat /tmp/it.txt" 
 exit;
}

function show_help_if_required()
{
 if [ "$1" == "help" ]
 then
 show_help
 fi
 if [ -z "$1" ]
 then
 show_help
 fi
}

function require_numeric_value()
{
 REG_EX='^[0-9]+$'
 if ! [[ $1 =~ $REG_EX ]] ; then
 show_help
 fi
}

show_help_if_required $1
require_numeric_value $1

DURATION=$1
shift

while :; do 
 clear
 echo "Updating every $DURATION seconds. Last updated $(date)"
 bash -c "$*"
 sleep $DURATION
done
</code></pre>

blocks|key|5096304|text|试试这个：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5096305|#!/bin/bash
#+usage:+watch+[-n+integer]+COMMAND

case+$#+in
++++0)
++++++++echo+"Usage+$0+[-n+int]+COMMAND"
++++++++;;
++++*)++++++
++++++++sleep=2;
++++++++;;
esac++++

if+[+"$1"+==+"-n"+];+then
++++sleep=$2
++++shift;+shift
fi


while+:;+
++++do+
++++clear;+
++++echo+"$(date)+every+${sleep}s+$@";+echo+
++++$@;+
++++sleep+$sleep;+
done|code-block|syntax|javascript|5096306|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Try this:

<pre><code>#!/bin/bash
# usage: watch [-n integer] COMMAND

case $# in
 0)
 echo "Usage $0 [-n int] COMMAND"
 ;;
 *) 
 sleep=2;
 ;;
esac 

if [ "$1" == "-n" ]; then
 sleep=$2
 shift; shift
fi


while :; 
 do 
 clear; 
 echo "$(date) every ${sleep}s $@"; echo 
 $@; 
 sleep $sleep; 
done
</code></pre>

blocks|key|5096336|text|如果watch不想通过|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5096337|brew+install+watch|code-block|syntax|javascript|5096338|还有另一个类似的/复制版本，它安装并完美地工作在我身上|5096339|brew+install+visionmedia-watch|5096340|https://github.com/tj/watch|offset|length|5096341|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|0|0|0|R|0|0^^$0|@$1|2|3|4|5|6|7|V|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|W|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|X|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|Y|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|Z|8|@]|9|@$M|10|N|11|1|12]]|A|$]]|$1|O|3|-4|5|6|7|13|8|@]|9|@]|A|$]]]|P|$Q|$5|R|S|T|A|$U|L]]]]

If watch doesn't want to install via 

<pre><code>brew install watch
</code></pre>

There is another similar/copy version that installed and worked perfectly for me

<pre><code>brew install visionmedia-watch
</code></pre>

<a href="https://github.com/tj/watch" rel="noreferrer">https://github.com/tj/watch</a>

blocks|key|1781606|text|为了防止主命令在可察觉的时间内完成时出现闪烁，您可以捕获输出并在完成时仅清除屏幕。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1781607|function+watch+{while+:;+do+a=$($@);+clear;+echo+"$(date)\n\n$a";+sleep+1;++done}|code-block|syntax|javascript|1781608|然后通过以下方式使用它：|1781609|watch+istats|1781610|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

To prevent flickering when your main command takes perceivable time to complete, you can capture the output and only clear screen when it's done.
<pre><code>function watch {while :; do a=$($@); clear; echo &quot;$(date)\n\n$a&quot;; sleep 1; done}
</code></pre>
Then use it by:
<pre><code>watch istats
</code></pre>

blocks|key|1781640|text|使用Nix包管理器！|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1781641|安装Nix，然后执行nix-env+-iA+nixpkgs.watch，在完成安装说明(包括在shell中获取.+"$HOME/.nix-profile/etc/profile.d/nix.sh"+)后，应该可以使用它。|style|CODE|1781642|entityMap|0|LINK|mutability|MUTABLE|url|https://nixos.org/nix/download.html^0|2|3|0|0|A|P|1J|17|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@$A|Q|B|R|1|S]]|C|$]]|$1|D|3|E|5|6|7|T|8|@$A|U|B|V|F|G]|$A|W|B|X|F|G]]|9|@]|C|$]]|$1|H|3|-4|5|6|7|Y|8|@]|9|@]|C|$]]]|I|$J|$5|K|L|M|C|$N|O]]]]

Use the <a href="https://nixos.org/nix/download.html" rel="nofollow noreferrer">Nix</a> package manager!
Install Nix, and then do <code>nix-env -iA nixpkgs.watch</code> and it should be available for use after the completing the install instructions (including sourcing <code>. &quot;$HOME/.nix-profile/etc/profile.d/nix.sh&quot;</code> in your shell).

I'm looking for the best way to duplicate the Linux 'watch' command on Mac OS X. I'd like to run a command every few seconds to pattern match on the contents of an output file using 'tail' and 'sed'.
What's my best option on a Mac, and can it be done without downloading software?

OS X Bash, 'watch' command

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我正在寻找在Mac OS X上复制Linux 'watch‘命令的最佳方法。我想每隔几秒钟运行一次命令，以便使用'tail’和'sed‘对输出文件的内容进行模式匹配。我在Mac上最好的选择是什么，不下载软件就能做到吗？

问OS X Bash，'watch‘命令
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问OS X Bash，'watch‘命令EN