blocks|key|4198697|text|您可以使用>&2将输出重定向到文件句柄2上的sdterr错误文件|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4198698|示例：|4198699|#+print+a+log+a+message
log+()
{
echo+"Log+message:+$1"+>&2
}

get_animals()
{
log+"Fetching+animals"
echo+"cat+dog+mouse"
}

values=`get_animals`
echo+$values|code-block|syntax|javascript|4198700|只接受标准输出上的输出，而不接受标准错误上的输出。另一方面，控制台同时显示两者。|4198701|如果你真的想要在标准输出中显示日志信息，你可以在给变量赋值后，将重定向回标准输出：|offset|length|style|BOLD|4198702|#+print+a+log+a+message
log+()
{
++++echo+"Log+message:+$1"+>&2
}

get_animals()
{
++++log+"Fetching+animals"
++++echo+"cat+dog+mouse"
}

values=`get_animals`+2>&1
echo+$values|4198703|entityMap^0|0|0|0|0|W|9|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|X|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|Y|8|@$M|Z|N|10|O|P]]|9|@]|A|$]]|$1|Q|3|R|5|F|7|11|8|@]|9|@]|A|$G|H]]|$1|S|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|T|$]]

You can redirect the output to the sdterr error file on file handle 2 using >&amp;2 

example :

<pre><code># print a log a message
log ()
{
echo "Log message: $1" &gt;&amp;2
}

get_animals()
{
log "Fetching animals"
echo "cat dog mouse"
}

values=`get_animals`
echo $values
</code></pre>

the `` only take the output on stdout, not on stderr. The console on the other hand displays both.

If you really want the Log message on the stdout you can redirect error back to stdout after assigning to the variable :

<pre><code># print a log a message
log ()
{
 echo "Log message: $1" &gt;&amp;2
}

get_animals()
{
 log "Fetching animals"
 echo "cat dog mouse"
}

values=`get_animals` 2&gt;&amp;1
echo $values
</code></pre>

blocks|key|4198730|text|您可以将日志输出重定向到标准错误流：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4198731|log()
{
++++echo+1>&2+"Log+message:+$1"
}|code-block|syntax|javascript|4198732|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|$]]

You could redirect log output to the standard error stream:

<pre><code>log()
{
 echo 1&gt;&amp;2 "Log message: $1"
}
</code></pre>

blocks|key|4198734|text|++++#
++++#------------------------------------------------------------------------------
++++#+echo+pass+params+and+print+them+to+a+log+file+and+terminal
++++#+with+timestamp+and+$host_name+and+$0+PID
++++#+usage:
++++#+doLog+"INFO+some+info+message"
++++#+doLog+"DEBUG+some+debug+message"
++++#+doLog+"WARN+some+warning+message"
++++#+doLog+"ERROR+some+really+ERROR+message"
++++#+doLog+"FATAL+some+really+fatal+message"
++++#------------------------------------------------------------------------------
++++doLog(){
++++++++type_of_msg=$(echo+$*%7Ccut+-d"+"+-f1)
++++++++msg=$(echo+"$*"%7Ccut+-d"+"+-f2-)
++++++++[[+$type_of_msg+==+DEBUG+]]+&&+[[+$do_print_debug_msgs+-ne+1+]]+&&+return
++++++++[[+$type_of_msg+==+INFO+]]+&&+type_of_msg="INFO+"+#+one+space+for+aligning
++++++++[[+$type_of_msg+==+WARN+]]+&&+type_of_msg="WARN+"+#+as+well

++++++++#+print+to+the+terminal+if+we+have+one
++++++++test+-t+1+&&+echo+"+[$type_of_msg]+`date+"%2B%25Y.%25m.%25d-%25H:%25M:%25S+%25Z"`+[$run_unit][@$host_name]+[$$]+""$msg"

++++++++#+define+default+log+file+none+specified+in+cnf+file
++++++++test+-z+$log_file+&&+\
++++++++++++mkdir+-p+$product_instance_dir/dat/log/bash+&&+\
++++++++++++++++log_file="$product_instance_dir/dat/log/bash/$run_unit.`date+"%2B%25Y%25m"`.log"
++++++++echo+"+[$type_of_msg]+`date+"%2B%25Y.%25m.%25d-%25H:%25M:%25S+%25Z"`+[$run_unit][@$host_name]+[$$]+""$msg"+>>+$log_file
++++}
++++#eof+func+doLog|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|4198735|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|$]]

<pre><code> #
 #------------------------------------------------------------------------------
 # echo pass params and print them to a log file and terminal
 # with timestamp and $host_name and $0 PID
 # usage:
 # doLog "INFO some info message"
 # doLog "DEBUG some debug message"
 # doLog "WARN some warning message"
 # doLog "ERROR some really ERROR message"
 # doLog "FATAL some really fatal message"
 #------------------------------------------------------------------------------
 doLog(){
 type_of_msg=$(echo $*|cut -d" " -f1)
 msg=$(echo "$*"|cut -d" " -f2-)
 [[ $type_of_msg == DEBUG ]] &amp;&amp; [[ $do_print_debug_msgs -ne 1 ]] &amp;&amp; return
 [[ $type_of_msg == INFO ]] &amp;&amp; type_of_msg="INFO " # one space for aligning
 [[ $type_of_msg == WARN ]] &amp;&amp; type_of_msg="WARN " # as well

 # print to the terminal if we have one
 test -t 1 &amp;&amp; echo " [$type_of_msg] `date "+%Y.%m.%d-%H:%M:%S %Z"` [$run_unit][@$host_name] [$$] ""$msg"

 # define default log file none specified in cnf file
 test -z $log_file &amp;&amp; \
 mkdir -p $product_instance_dir/dat/log/bash &amp;&amp; \
 log_file="$product_instance_dir/dat/log/bash/$run_unit.`date "+%Y%m"`.log"
 echo " [$type_of_msg] `date "+%Y.%m.%d-%H:%M:%S %Z"` [$run_unit][@$host_name] [$$] ""$msg" &gt;&gt; $log_file
 }
 #eof func doLog
</code></pre>

blocks|key|4198776|text|choroba's+solution+to+another+question展示了如何使用exec打开一个新的文件描述符。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|4198777|将这个解决方案翻译成这个问题，可以得到如下结果：|4198778|#+Open+a+new+file+descriptor+that+redirects+to+stdout:
exec+3>&1

log+()
{
++++echo+"Log+message:+$1"+1>&3
}

get_animals()
{
++++log+"Fetching+animals"
++++echo+"cat+dog+mouse"
}

animals=`get_animals`
echo+Animals:+$animals|code-block|syntax|javascript|4198779|执行上述命令会产生以下结果：|4198780|Log+message:+Fetching+animals
Animals:+cat+dog+mouse|4198781|有关在Bash中使用I/O重定向和文件描述符的更多信息，请访问：|4198782|4198783|Bash+Guide+for+Beginners,+section+8.2.3,+Redirection+and+file+descriptors|unordered-list-item|4198784|Advanced+Bash-Scripting+Guide,+Chapter+20,+I/O+Redirection|4198785|4198786|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/18101327|1|http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_08_02.html#sect_08_02_03|2|http://www.tldp.org/LDP/abs/html/io-redirection.html^0|0|12|0|0|0|0|0|0|0|0|0|21|1|0|0|1M|2|0|0^^$0|@$1|2|3|4|5|6|7|19|8|@]|9|@$A|1A|B|1B|1|1C]]|C|$]]|$1|D|3|E|5|6|7|1D|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|1E|8|@]|9|@]|C|$I|J]]|$1|K|3|L|5|6|7|1F|8|@]|9|@]|C|$]]|$1|M|3|N|5|H|7|1G|8|@]|9|@]|C|$I|J]]|$1|O|3|P|5|6|7|1H|8|@]|9|@]|C|$]]|$1|Q|3|-4|5|6|7|1I|8|@]|9|@]|C|$]]|$1|R|3|S|5|T|7|1J|8|@]|9|@$A|1K|B|1L|1|1M]]|C|$]]|$1|U|3|V|5|T|7|1N|8|@]|9|@$A|1O|B|1P|1|1Q]]|C|$]]|$1|W|3|-4|5|6|7|1R|8|@]|9|@]|C|$]]|$1|X|3|-4|5|6|7|1S|8|@]|9|@]|C|$]]]|Y|$Z|$5|10|11|12|C|$13|14]]|15|$5|10|11|12|C|$13|16]]|17|$5|10|11|12|C|$13|18]]]]

<a href="https://stackoverflow.com/a/18101327">choroba's solution to another question</a> shows how to use exec to open a new file descriptor.

Translating that solution to this question gives something like:

<pre><code># Open a new file descriptor that redirects to stdout:
exec 3&gt;&amp;1

log ()
{
 echo "Log message: $1" 1&gt;&amp;3
}

get_animals()
{
 log "Fetching animals"
 echo "cat dog mouse"
}

animals=`get_animals`
echo Animals: $animals
</code></pre>

Executing the above produces:

<pre><code>Log message: Fetching animals
Animals: cat dog mouse
</code></pre>

More information about using I/O redirection and file descriptors in Bash can be found at:

<ul>
<li><a href="http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_08_02.html#sect_08_02_03" rel="noreferrer">Bash Guide for Beginners, section 8.2.3, Redirection and file descriptors</a></li>
<li><a href="http://www.tldp.org/LDP/abs/html/io-redirection.html" rel="noreferrer">Advanced Bash-Scripting Guide, Chapter 20, I/O Redirection</a></li>
</ul>

I'd like to be able to put log messages in the middle of bash functions, without affecting the output of those very functions. For example, consider the following functions <code>log()</code> and <code>get_animals()</code>:

<pre><code># print a log a message
log ()
{
 echo "Log message: $1"
}

get_animals()
{
 log "Fetching animals"
 echo "cat dog mouse"
}

values=`get_animals`
echo $values
</code></pre>

After which <code>$values</code> contains the string <code>"Log message: Fetching animals cat dog mouse"</code>.

How should I modify this script so that <code>"Log message: Fetching animals"</code> is outputted to the terminal, and <code>$values</code> contains <code>"cat dog mouse"</code>?

Logging functions in bash and stdout

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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我希望能够将日志消息放在bash函数的中间，而不会影响这些函数的输出。例如，考虑以下函数log()和get_animals()# print a log a messagelog (){    echo "Log message: $1"}get_animals(){    log "Fetching animals"...

问bash和stdout中的日志函数
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问bash和stdout中的日志函数EN