blocks|key|1467714|text|通常我们会将其中一个放在脚本的顶部或靠近脚本的顶部。解析其命令行的脚本将在解析后执行重定向。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1467715|将stdout发送到文件|1467716|exec+>+file|code-block|syntax|javascript|1467717|使用stderr|1467718|exec+>+file++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
exec+2>&1|1467719|将stdout和stderr都追加到文件|1467720|exec+>>+file
exec+2>&1|1467721|作为Jonathan+Leffler+mentioned+in+his+comment|offset|length|1467722|exec有两个独立的工作。第一种方法是用新程序替换当前正在执行的shell+(脚本)。另一个是更改当前shell中的I/O重定向。这一点的区别在于没有exec参数。|style|CODE|1467723|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/users/15168/jonathan-leffler|1|https://stackoverflow.com/questions/314675/how-do-i-redirect-the-output-of-an-entire-shell-script-within-the-script-itself#comment68457734_314678^0|0|0|0|0|0|0|0|2|G|0|J|O|1|0|0|4|23|4|0^^$0|@$1|2|3|4|5|6|7|18|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|19|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|1A|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|1B|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|1C|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|1D|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|1E|8|@]|9|@]|A|$G|H]]|$1|Q|3|R|5|6|7|1F|8|@]|9|@$S|1G|T|1H|1|1I]|$S|1J|T|1K|1|1L]]|A|$]]|$1|U|3|V|5|6|7|1M|8|@$S|1N|T|1O|W|X]|$S|1P|T|1Q|W|X]]|9|@]|A|$]]|$1|Y|3|-4|5|6|7|1R|8|@]|9|@]|A|$]]]|Z|$10|$5|11|12|13|A|$14|15]]|16|$5|11|12|13|A|$14|17]]]]

Typically we would place one of these at or near the top of the script. Scripts that parse their command lines would do the redirection after parsing.

Send stdout to a file

<pre><code>exec &gt; file
</code></pre>

with stderr

<pre><code>exec &gt; file 
exec 2&gt;&amp;1
</code></pre>

append both stdout and stderr to file

<pre><code>exec &gt;&gt; file
exec 2&gt;&amp;1
</code></pre>

As <a href="https://stackoverflow.com/users/15168/jonathan-leffler">Jonathan Leffler</a> <a href="https://stackoverflow.com/questions/314675/how-do-i-redirect-the-output-of-an-entire-shell-script-within-the-script-itself#comment68457734_314678">mentioned in his comment</a>:

<code>exec</code> has two separate jobs. The first one is to replace the currently executing shell (script) with a new program. The other is changing the I/O redirections in the current shell. This is distinguished by having no argument to <code>exec</code>.

blocks|key|1467773|text|您可以使整个脚本成为如下所示的函数：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1467774|main_function()+{
++do_things_here
}|code-block|syntax|javascript|1467775|然后，在脚本的末尾添加以下内容：|1467776|if+[+-z+$TERM+];+then
++#+if+not+run+via+terminal,+log+everything+into+a+log+file
++main_function+2>&1+>>+/var/log/my_uber_script.log
else
++#+run+via+terminal,+only+output+to+screen
++main_function
fi|1467777|或者，您可以在每次运行时将所有内容都记录到日志文件中，然后通过简单的操作将其输出到stdout：|1467778|#+log+everything,+but+also+output+to+stdout
main_function+2>&1+%7C+tee+-a+/var/log/my_uber_script.log|1467779|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|U|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

You can make the whole script a function like this:

<pre><code>main_function() {
 do_things_here
}
</code></pre>

then at the end of the script have this:

<pre><code>if [ -z $TERM ]; then
 # if not run via terminal, log everything into a log file
 main_function 2&gt;&amp;1 &gt;&gt; /var/log/my_uber_script.log
else
 # run via terminal, only output to screen
 main_function
fi
</code></pre>

Alternatively, you may log everything into logfile each run and still output it to stdout by simply doing:

<pre><code># log everything, but also output to stdout
main_function 2&gt;&amp;1 | tee -a /var/log/my_uber_script.log
</code></pre>

blocks|key|1467787|text|[+-t+<&0+]+%7C%7C+exec+>>+test.log|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1467788|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

blocks|key|1467841|text|要保存原始stdout和stderr，您可以使用：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1467842|exec+[fd+number]<&1+
exec+[fd+number]<&2|code-block|syntax|javascript|1467843|例如，以下代码将把"walla1“和"walla2”输出到日志文件(a.txt)，将"walla3“输出到stdout，将"walla4”输出到stderr。|offset|length|style|CODE|1467844|#!/bin/bash

exec+5<&1
exec+6<&2

exec+1>+~/a.txt+2>&1

echo+"walla1"
echo+"walla2"+>&2
echo+"walla3"+>&5
echo+"walla4"+>&6|1467845|entityMap^0|0|0|Y|5|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@$I|T|J|U|K|L]]|9|@]|A|$]]|$1|M|3|N|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

For saving the original stdout and stderr you can use: 

<pre><code>exec [fd number]&lt;&amp;1 
exec [fd number]&lt;&amp;2
</code></pre>

For example, the following code will print "walla1" and "walla2" to the log file (<code>a.txt</code>), "walla3" to stdout, "walla4" to stderr.

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

exec 5&lt;&amp;1
exec 6&lt;&amp;2

exec 1&gt; ~/a.txt 2&gt;&amp;1

echo "walla1"
echo "walla2" &gt;&amp;2
echo "walla3" &gt;&amp;5
echo "walla4" &gt;&amp;6
</code></pre>

Is it possible to redirect all of the output of a Bourne shell script to somewhere, but with shell commands inside the script itself?
Redirecting the output of a single command is easy, but I want something more like this:
<pre><code>#!/bin/sh
if [ ! -t 0 ]; then
 # redirect all of my output to a file here
fi

# rest of script...
</code></pre>
Meaning: if the script is run non-interactively (for example, cron), save off the output of everything to a file. If run interactively from a shell, let the output go to stdout as usual.
I want to do this for a script normally run by the FreeBSD periodic utility. It's part of the daily run, which I don't normally care to see every day in email, so I don't have it sent. However, if something inside this one particular script fails, that's important to me and I'd like to be able to capture and email the output of this one part of the daily jobs.
Update: Joshua's answer is spot-on, but I also wanted to save and restore stdout and stderr around the entire script, which is done like this:
<pre><code># save stdout and stderr to file 
# descriptors 3 and 4, 
# then redirect them to &quot;foo&quot;
exec 3&gt;&amp;1 4&gt;&amp;2 &gt;foo 2&gt;&amp;1

# ...

# restore stdout and stderr
exec 1&gt;&amp;3 2&gt;&amp;4
</code></pre>

How to redirect output of an entire shell script within the script itself?

日志文件

FreeBSD

有没有可能将Bourne shell脚本的所有输出重定向到某个地方，但脚本本身包含shell命令？重定向单个命令的输出很简单，但我想要更多这样的输出：#!/bin/shif [ ! -t 0 ]; then    # redirect all of my output to a file herefi# rest of...

问如何在脚本本身中重定向整个shell脚本的输出？
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