blocks|key|3504078|text|bash中并没有真正的try/catch+(我假设您正在使用bash)，但是您可以使用&&或%7C%7C来实现非常类似的行为。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3504079|在此示例中，如果a_command+失败(返回一个非零值)，则要运行：|3504080|a_command+%7C%7C+fallback_command|code-block|syntax|javascript|3504081|在此示例中，如果a_command+成功执行(返回0)，则希望执行：|BOLD|3504082|a_command+&&+second_command|3504083|通过使用子subshell可以很容易地将它们混合在一起，例如，以下命令将执行a_command，如果成功，它将运行other_command，但如果a_command或other_command失败，则将执行fallback_command：|3504084|(a_command+&&+other_command)+%7C%7C+fallback_command|3504085|entityMap^0|B|9|17|2|1A|2|0|8|9|0|0|8|9|I|4|0|0|12|9|1L|D|22|9|2C|D|2W|G|0|0^^$0|@$1|2|3|4|5|6|7|X|8|@$9|Y|A|Z|B|C]|$9|10|A|11|B|C]|$9|12|A|13|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|14|8|@$9|15|A|16|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|17|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|18|8|@$9|19|A|1A|B|C]|$9|1B|A|1C|B|O]]|D|@]|E|$]]|$1|P|3|Q|5|J|7|1D|8|@]|D|@]|E|$K|L]]|$1|R|3|S|5|6|7|1E|8|@$9|1F|A|1G|B|C]|$9|1H|A|1I|B|C]|$9|1J|A|1K|B|C]|$9|1L|A|1M|B|C]|$9|1N|A|1O|B|C]]|D|@]|E|$]]|$1|T|3|U|5|J|7|1P|8|@]|D|@]|E|$K|L]]|$1|V|3|-4|5|6|7|1Q|8|@]|D|@]|E|$]]]|W|$]]

There is not really a <code>try/catch</code> in bash (i assume you're using bash), but you can achieve a quite similar behaviour using <code>&amp;&amp;</code> or <code>||</code>.

In this example, you want to run <code>fallback_command</code> if <code>a_command</code> fails (returns a non-zero value):

<pre><code>a_command || fallback_command
</code></pre>

And in this example, you want to execute <code>second_command</code> if <code>a_command</code> is successful (returns 0):

<pre><code>a_command &amp;&amp; second_command
</code></pre>

They can easily be mixed together by using a subshell, for example, the following command will execute <code>a_command</code>, if it succeeds it will then run <code>other_command</code>, but if <code>a_command</code> or <code>other_command</code> fails, <code>fallback_command</code> will be executed:

<pre><code>(a_command &amp;&amp; other_command) || fallback_command
</code></pre>

blocks|key|3789219|text|if/else结构和退出代码可以帮助您伪造一些代码。这应该可以在Bash或Bourne+(sh)中工作。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3789220|if+foo+;+then
else
++e=$?++++++++#+return+code+from+if
++if+[+"${e}"+-eq+"1"];+then
++++echo+"Foo+returned+exit+code+1"
++elif+[+"${e}"+-gt+"1"];+then
++++echo+"Foo+returned+BAD+exit+code+${e}"
++fi
fi|code-block|syntax|javascript|3789221|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|$]]

The if/else structure and exit codes can help you fake some of it. This should work in Bash or Bourne (sh).

<pre><code>if foo ; then
else
 e=$? # return code from if
 if [ "${e}" -eq "1"]; then
 echo "Foo returned exit code 1"
 elif [ "${e}" -gt "1"]; then
 echo "Foo returned BAD exit code ${e}"
 fi
fi
</code></pre>

blocks|key|3789251|text|{
++++#+command+which+may+fail+and+give+an+error+
}+%7C%7C+{
+++#+command+which+should+be+run+instead+of+the+above+failing++++++command
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|3789252|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>{
 # command which may fail and give an error 
} || {
 # command which should be run instead of the above failing command
}
</code></pre>

blocks|key|3789239|text|以下是bash中的two+simple+bashfunctions+which+enable+eventhandling：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3789240|您可以使用它进行基本的异常处理，如下所示：|3789241|onFoo(){
++echo+"onFoo()+called+width+arg+$1!"
}++

foo(){
++[[+-f+/tmp/somefile+]]+%7C%7C+throw+EXCEPTION_FOO_OCCURED+"some+arg"
}+

addListener+EXCEPTION_FOO_OCCURED+onFoo|code-block|syntax|javascript|3789242|使用try/catch块的异常处理在bash中是不受支持的，但是你可能想看看支持它的BANGSH框架(它有点像bash的jquery+)。|3789243|然而，没有级联try/catch块的异常处理类似于eventhandling，，在几乎所有支持数组的语言中，都是可能的。|style|BOLD|3789244|如果你想让你的代码保持整洁(不需要if/else冗长)，我建议使用事件。|3789245|对于函数，不推荐使用MatToufoutu推荐的建议(使用%7C%7C和&&)，但对于简单的命令，可以。(有关风险，请参阅BashPitfalls+)|3789246|entityMap|0|LINK|mutability|MUTABLE|url|https://gist.github.com/coderofsalvation/8268365|1|http://mywiki.wooledge.org/BashPitfalls#cmd1_.26.26_cmd2_.7C.7C_cmd3^0|9|1F|0|0|0|0|0|P|D|1I|2|0|0|19|Q|1L|C|1|0^^$0|@$1|2|3|4|5|6|7|14|8|@]|9|@$A|15|B|16|1|17]]|C|$]]|$1|D|3|E|5|6|7|18|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|19|8|@]|9|@]|C|$I|J]]|$1|K|3|L|5|6|7|1A|8|@]|9|@]|C|$]]|$1|M|3|N|5|6|7|1B|8|@$A|1C|B|1D|O|P]|$A|1E|B|1F|O|P]]|9|@]|C|$]]|$1|Q|3|R|5|6|7|1G|8|@]|9|@]|C|$]]|$1|S|3|T|5|6|7|1H|8|@$A|1I|B|1J|O|P]]|9|@$A|1K|B|1L|1|1M]]|C|$]]|$1|U|3|-4|5|6|7|1N|8|@]|9|@]|C|$]]]|V|$W|$5|X|Y|Z|C|$10|11]]|12|$5|X|Y|Z|C|$10|13]]]]

Here are <a href="https://gist.github.com/coderofsalvation/8268365" rel="nofollow">two simple bashfunctions which enable eventhandling</a> in bash:

You could use it for basic exceptionhandling like this:

<pre><code>onFoo(){
 echo "onFoo() called width arg $1!"
} 

foo(){
 [[ -f /tmp/somefile ]] || throw EXCEPTION_FOO_OCCURED "some arg"
} 

addListener EXCEPTION_FOO_OCCURED onFoo
</code></pre>

Exceptionhandling using try/catch blocks is not supported in bash, however, you might wanna try looking at the BANGSH framework which supports it (its a bit like jquery for bash).

However, exceptionhandling without cascading try/catch-blocks is similar to eventhandling, which is possible in almost any language with array-support.

If you want to keep your code nice and tidy (without if/else verbosity), I would recommend to use events.

The suggestion which MatToufoutu recommends (using || and &amp;&amp;) is not recommended for functions, but ok for simple commands. (see <a href="http://mywiki.wooledge.org/BashPitfalls#cmd1_.26.26_cmd2_.7C.7C_cmd3" rel="nofollow">BashPitfalls</a> about the risks)

blocks|key|177018|text|在error_exit是接受一个参数的函数的情况下，使用下面的方法来正确处理错误。如果没有传递参数，那么它将抛出未知错误，并在实际发生错误的地方抛出LineNo。请在实际用于生产之前进行实验-|type|unstyled|depth|inlineStyleRanges|entityRanges|data|177019|#!/bin/bash

PROGNAME=$(basename+$0)

error_exit()

{

++++echo+"${PROGNAME}:+${1:-"Unknown+Error"}"+1>&2
++++exit+1
}

echo+"Example+of+error+with+line+number+and+message"
error_exit+"$LINENO:+An+error+has+occurred."|code-block|syntax|javascript|177020|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|$]]

Use following to handle error properly where error_exit is function that accepts one argument. In case if argument is not passed then it will throw unknown error with LineNo where actually error is happening. Please experiment before actually uses for production -

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

PROGNAME=$(basename $0)

error_exit()

{

 echo "${PROGNAME}: ${1:-"Unknown Error"}" 1&gt;&amp;2
 exit 1
}

echo "Example of error with line number and message"
error_exit "$LINENO: An error has occurred."
</code></pre>

I'm looking for exception handling mechanism in shell script. Is there any try,catch equivalent mechanism in shell script ?

Exception handling in shell scripting?

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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