blocks|key|358354|text|如果您想在注销后保持进程运行，请执行：|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|358355|disown+-h+<pid>|CODE|358356|是一个很有用的内置bash。与nohup不同，您可以在已经运行的进程上运行disown。|358357|首先，使用control-Z停止您的作业，从ps获取pid+(或使用echo+$!)，使用bg将其发送到后台，然后使用带有-h标志的disown。|358358|别忘了给你的工作设置后台，否则当你注销的时候它会被杀死。|358359|entityMap^0|I|1|0|0|F|0|F|5|11|6|0|M|2|Y|7|19|2|1U|6|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|T|8|@$9|U|A|V|B|H]]|D|@]|E|$]]|$1|I|3|J|5|6|7|W|8|@$9|X|A|Y|B|H]|$9|Z|A|10|B|H]]|D|@]|E|$]]|$1|K|3|L|5|6|7|11|8|@$9|12|A|13|B|H]|$9|14|A|15|B|H]|$9|16|A|17|B|H]|$9|18|A|19|B|H]]|D|@]|E|$]]|$1|M|3|N|5|6|7|1A|8|@]|D|@]|E|$]]|$1|O|3|-4|5|6|7|1B|8|@]|D|@]|E|$]]]|P|$]]

If you want to keep a process running after you log out:

<code>disown -h &lt;pid&gt;</code> 

is a useful bash built-in. Unlike <code>nohup</code>, you can run <code>disown</code> on an already-running process.

First, stop your job with control-Z, get the pid from <code>ps</code> (or use <code>echo $!</code>), use <code>bg</code> to send it to the background, then use <code>disown</code> with the -h flag. 

Don't forget to background your job or it will be killed when you logout.

blocks|key|3148238|text|手册中扩展部分列出的几乎所有内容|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3148239|具体来说，参数扩展：|3148240|$+I=foobar
$+echo+${I/oo/aa}+#replacement
faabar
$+echo+${I:1:2}+++#substring
oo
$+echo+${I%25bar}+++#trailing+substitution
foo
$+echo+${I#foo}+++#leading+substitution
bar|code-block|syntax|javascript|3148241|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Almost everything listed under EXPANSION section in the manual

In particular, parameter expansion:

<pre><code>$ I=foobar
$ echo ${I/oo/aa} #replacement
faabar
$ echo ${I:1:2} #substring
oo
$ echo ${I%bar} #trailing substitution
foo
$ echo ${I#foo} #leading substitution
bar
</code></pre>

blocks|key|3148899|text|我的最爱：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3148900|sudo+!!|code-block|syntax|javascript|3148901|使用sudo重新运行前面的命令。|3148902|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

My favorite:

<pre><code>sudo !!
</code></pre>

Rerun the previous command with sudo.

blocks|key|360373|text|获取历史记录命令和参数|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|360374|可以使用!操作符有选择地访问以前的命令和参数。当您使用长路径时，它非常有用。|CODE|360375|您可以使用history检查您的最后一个命令。|360376|您可以使用以前的命令，其中!<n>是history中命令的索引，负数从历史上的最后一个命令开始倒数。|360377|ls+-l+foo+bar
touch+foo+bar
!-2|code-block|syntax|javascript|360378|您可以将前面的参数与!:<n>一起使用，0是命令，>=+1是参数。|360379|ls+-l+foo
touch+!:2
cp+!:1+bar|360380|您可以使用!<n>:<m>将这两者结合起来|360381|touch+foo+bar
ls+-l+!:1+!:2
rm+!-2:1+!-2:2
!-2|360382|您还可以使用参数范围!<n>:<x>-<y>|360383|touch+boo+far
ls+-l+!:1-2|360384|其他!特殊修饰符包括：|360385|所有参数的|360386|*|unordered-list-item|360387|360388|对于第一个参数，ls+-l+foo+bar+ls+!*|360389|%5E+(对于最后一个参数，!%5E)|360390|
|360391|$为!:1+==|360392|360393|ls+-l+foo+bar+cat+!$+>+/dev/null|360394|entityMap^0|0|B|0|4|1|0|5|7|0|D|4|I|7|0|0|A|5|0|0|5|8|0|0|A|C|0|0|2|1|0|0|0|1|0|0|0|0|1|C|2|0|0|0|1|2|3|0|0|0^^$0|@$1|2|3|4|5|6|7|1O|8|@$9|1P|A|1Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|1R|8|@$9|1S|A|1T|B|H]]|D|@]|E|$]]|$1|I|3|J|5|6|7|1U|8|@$9|1V|A|1W|B|H]]|D|@]|E|$]]|$1|K|3|L|5|6|7|1X|8|@$9|1Y|A|1Z|B|H]|$9|20|A|21|B|H]]|D|@]|E|$]]|$1|M|3|N|5|O|7|22|8|@]|D|@]|E|$P|Q]]|$1|R|3|S|5|6|7|23|8|@$9|24|A|25|B|H]]|D|@]|E|$]]|$1|T|3|U|5|O|7|26|8|@]|D|@]|E|$P|Q]]|$1|V|3|W|5|6|7|27|8|@$9|28|A|29|B|H]]|D|@]|E|$]]|$1|X|3|Y|5|O|7|2A|8|@]|D|@]|E|$P|Q]]|$1|Z|3|10|5|6|7|2B|8|@$9|2C|A|2D|B|H]]|D|@]|E|$]]|$1|11|3|12|5|O|7|2E|8|@]|D|@]|E|$P|Q]]|$1|13|3|14|5|6|7|2F|8|@$9|2G|A|2H|B|H]]|D|@]|E|$]]|$1|15|3|16|5|6|7|2I|8|@]|D|@]|E|$]]|$1|17|3|18|5|19|7|2J|8|@$9|2K|A|2L|B|H]]|D|@]|E|$]]|$1|1A|3|-4|5|6|7|2M|8|@]|D|@]|E|$]]|$1|1B|3|1C|5|6|7|2N|8|@]|D|@]|E|$]]|$1|1D|3|1E|5|19|7|2O|8|@$9|2P|A|2Q|B|H]|$9|2R|A|2S|B|H]]|D|@]|E|$]]|$1|1F|3|1G|5|6|7|2T|8|@]|D|@]|E|$]]|$1|1H|3|1I|5|19|7|2U|8|@$9|2V|A|2W|B|H]|$9|2X|A|2Y|B|H]]|D|@]|E|$]]|$1|1J|3|-4|5|6|7|2Z|8|@]|D|@]|E|$]]|$1|1K|3|1L|5|6|7|30|8|@]|D|@]|E|$]]|$1|1M|3|-4|5|6|7|31|8|@]|D|@]|E|$]]]|1N|$]]

Get back history commands and arguments

It's possible to selectively access previous commands and arguments using the <code>!</code> operator. It's very useful when you are working with long paths.

You can check your last commands with <code>history</code>.

You can use previous commands with <code>!&lt;n&gt;</code> being <code>n</code> the index of the command in <code>history</code>, negative numbers count backwards from the last command in history.

<pre><code>ls -l foo bar
touch foo bar
!-2
</code></pre>

You can use previous arguments with <code>!:&lt;n&gt;</code>, zero is the command, >= 1 are the arguments.

<pre><code>ls -l foo
touch !:2
cp !:1 bar
</code></pre>

And you can combine both with <code>!&lt;n&gt;:&lt;m&gt;</code>

<pre><code>touch foo bar
ls -l !:1 !:2
rm !-2:1 !-2:2
!-2
</code></pre>

You can also use argument ranges <code>!&lt;n&gt;:&lt;x&gt;-&lt;y&gt;</code>

<pre><code>touch boo far
ls -l !:1-2
</code></pre>

Other <code>!</code> special modifiers are:

<ul>
<li><code>*</code> for all the arguments

<pre><code>ls -l foo bar
ls !*
</code></pre></li>
<li><code>^</code> for the first argument (<code>!:1</code> == <code>!^</code>)</li>
<li><code>$</code> for the last argument

<pre><code>ls -l foo bar
cat !$ &gt; /dev/null
</code></pre></li>
</ul>

blocks|key|3148221|text|我喜欢-x特性，它允许查看脚本中发生的事情。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3148222|bash+-x+script.sh+|code-block|syntax|javascript|3148223|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|$]]

I like the -x feature, allowing to see what's going on in your script.

<pre><code>bash -x script.sh 
</code></pre>

blocks|key|3361441|text|SECONDS=0;+sleep+5+;+echo+"that+took+approximately+$SECONDS+seconds"|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3361442|3361443|+秒数|blockquote|BOLD|3361444|3361445|每次引用此参数时，返回自shell调用以来的秒数。如果将某个值赋给秒数，则后续引用时返回的值是赋值后的秒数加上赋值后的秒数。如果取消设置秒数，它将失去其特殊属性，即使随后被重置也是如此。|3361446|entityMap^0|0|1W|0|0|1|2|0|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|S|8|@]|D|@]|E|$]]|$1|G|3|H|5|I|7|T|8|@$9|U|A|V|B|J]]|D|@]|E|$]]|$1|K|3|-4|5|6|7|W|8|@]|D|@]|E|$]]|$1|L|3|M|5|6|7|X|8|@]|D|@]|E|$]]|$1|N|3|-4|5|6|7|Y|8|@]|D|@]|E|$]]]|O|$]]

<code>SECONDS=0; sleep 5 ; echo &quot;that took approximately $SECONDS seconds&quot;</code>
<blockquote>
SECONDS
Each time this parameter is
referenced, the number of seconds
since shell invocation is returned.
If a value is assigned to SECONDS,
the value returned upon subsequent
references is the number of seconds
since the assignment plus the value
assigned. If SECONDS is unset, it
loses its special properties, even if
it is subsequently reset.
</blockquote>

blocks|key|3148594|text|这是我的最爱之一。这会将制表符完成设置为不区分大小写。它非常适合快速输入目录路径，特别是在Mac上，默认情况下文件系统不区分大小写。我把它放在主文件夹的.inputrc中。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3148595|set+completion-ignore-case+on|code-block|syntax|javascript|3148596|entityMap^0|24|8|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

Here is one of my favorites. This sets tab completion to not be case sensitive. It's really great for quickly typing directory paths, especially on a Mac where the file system is not case sensitive by default. I put this in <code>.inputrc</code> in my home folder.

<pre><code>set completion-ignore-case on
</code></pre>

blocks|key|362908|text|特殊变量random：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|362909|if+[[+$(($RANDOM+%25+6))+=+0+]]
++++then+echo+"BANG"
else
++++echo+"Try+again"
fi+++|code-block|syntax|javascript|362910|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 special variable random:

<pre><code>if [[ $(($RANDOM % 6)) = 0 ]]
 then echo "BANG"
else
 echo "Try again"
fi 
</code></pre>

blocks|key|363013|text|处理的正则表达式|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|363014|最近的bash版本提供了正则表达式匹配功能，因此您可以执行以下操作：|363015|if+[[+"mystring"+=~+REGEX+]]+;+then++
++++echo+match
fi|code-block|syntax|javascript|363016|其中，REGEX是采用man+re_format描述的格式的原始正则表达式。|363017|任何带括号的部分的匹配项都存储在BASH_REMATCH数组中，从元素1开始(元素0是整个匹配的字符串)，因此您也可以使用它来执行正则表达式支持的解析。|363018|entityMap^0|3|5|0|0|Y|0|0|0|12|0|0|24|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|V|8|@$9|W|A|X|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|Y|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|Z|8|@$9|10|A|11|B|C]]|D|@]|E|$]]|$1|O|3|P|5|6|7|12|8|@$9|13|A|14|B|C]]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|15|8|@]|D|@]|E|$]]]|R|$]]

Regular expression handling

Recent bash releases feature regular expression matching, so you can do:

<pre><code>if [[ "mystring" =~ REGEX ]] ; then 
 echo match
fi
</code></pre>

where REGEX is a raw regular expression in the format described by man re_format.

Matches from any bracketed parts are stored in the BASH_REMATCH array, starting at element 1 (element 0 is the matched string in its entirety), so you can use this to do regex-powered parsing too.

blocks|key|359747|text|快速和粗略地纠正打字错误(特别适用于连接速度较慢的长命令，在这种情况下，使用命令历史记录和滚动它将是可怕的)：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|359748|$+cat+/proc/cupinfo
cat:+/proc/cupinfo:+No+such+file+or+directory
$+%5Ecup%5Ecpu|code-block|syntax|javascript|359749|还可以尝试!:s/old/new，它会在前面的命令中用新旧替换一次旧的。|offset|length|style|CODE|359750|如果您想替换多个实例，您可以使用!:gs/old/new进行全局替换。|359751|您可以对任何历史事件使用gs和s命令，例如|359752|!-2:s/old/new|359753|在倒数第二个命令中用new+(once)替换old。|359754|entityMap^0|0|0|5|B|0|G|C|0|C|2|F|1|0|0|A|3|M|3|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Y|8|@$I|Z|J|10|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|11|8|@$I|12|J|13|K|L]]|9|@]|A|$]]|$1|O|3|P|5|6|7|14|8|@$I|15|J|16|K|L]|$I|17|J|18|K|L]]|9|@]|A|$]]|$1|Q|3|R|5|D|7|19|8|@]|9|@]|A|$E|F]]|$1|S|3|T|5|6|7|1A|8|@$I|1B|J|1C|K|L]|$I|1D|J|1E|K|L]]|9|@]|A|$]]|$1|U|3|-4|5|6|7|1F|8|@]|9|@]|A|$]]]|V|$]]

Quick &amp; Dirty correction of typos (especially useful for long commands over slow connections where using the command history and scrolling through it would be horrible):

<pre><code>$ cat /proc/cupinfo
cat: /proc/cupinfo: No such file or directory
$ ^cup^cpu
</code></pre>

Also try <code>!:s/old/new</code> which substitutes old with new in the previous command once. 

If you want to substitute many occurrences you can do a global substitution with <code>!:gs/old/new</code>. 

You can use the <code>gs</code> and <code>s</code> commands with any history event, e.g.

<pre><code>!-2:s/old/new
</code></pre>

To substitute <code>old</code> with <code>new</code> (once) in the second to last command.

blocks|key|362954|text|下面是我最喜欢的两个例子：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|362955|要检查没有真正执行脚本的语法，请使用以下命令：|362956|bash+-n+script.sh|code-block|syntax|javascript|362957|返回到最后一个目录(是的，我知道pushd和popd，但这样更快)|362958|cd+-|362959|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Here two of my favorites:

To check the syntax w/o really executing the script use:

<pre><code>bash -n script.sh
</code></pre>

Go back to the last directory (yes I know pushd and popd, but this is quicker)

<pre><code>cd -
</code></pre>

blocks|key|3360931|text|使用中缀布尔运算符的|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3360932|考虑一下简单的if：|offset|length|style|BOLD|3360933|if+[+2+-lt+3+]
++++then+echo+"Numbers+are+still+good!"
fi|code-block|syntax|javascript|3360934|那个-lt看起来有点丑陋。不是很现代。如果你用双括号括起你的布尔表达式，你可以使用普通的布尔运算符！|3360935|if+[[+2+<+3+]]
++++then+echo+"Numbers+are+still+good!"
fi|3360936|entityMap^0|0|0|A|0|0|0|1E|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@$D|U|E|V|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|W|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|X|8|@$D|Y|E|Z|F|G]]|9|@]|A|$]]|$1|O|3|P|5|J|7|10|8|@]|9|@]|A|$K|L]]|$1|Q|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|R|$]]

Using Infix Boolean Operators

Consider the simple if:

<pre><code>if [ 2 -lt 3 ]
 then echo "Numbers are still good!"
fi
</code></pre>

That -lt looks kinda ugly. Not very modern. If you use double brackets around your boolean expression you can the normal boolean operators!

<pre><code>if [[ 2 &lt; 3 ]]
 then echo "Numbers are still good!"
fi
</code></pre>

blocks|key|3148263|text|数组：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3148264|#!/bin/bash

array[0]="a+string"
array[1]="a+string+with+spaces+and+\"quotation\"+marks+in+it"
array[2]="a+string+with+spaces,+\"quotation+marks\"+and+(parenthesis)+in+it"

echo+"There+are+${#array[*]}+elements+in+the+array."
for+n+in+"${array[@]}";+do
++++echo+"element+=+>>${n}<<"
done|code-block|syntax|javascript|3148265|有关数组(以及其他高级bash脚本)的更多详细信息，可以在Advanced+Bash-Scripting+Guide中找到。|offset|length|3148266|entityMap|0|LINK|mutability|MUTABLE|url|http://tldp.org/LDP/abs/html/^0|0|0|T|T|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]]|$1|G|3|H|5|6|7|U|8|@]|9|@$I|V|J|W|1|X]]|A|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

Arrays:

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

array[0]="a string"
array[1]="a string with spaces and \"quotation\" marks in it"
array[2]="a string with spaces, \"quotation marks\" and (parenthesis) in it"

echo "There are ${#array[*]} elements in the array."
for n in "${array[@]}"; do
 echo "element = &gt;&gt;${n}&lt;&lt;"
done
</code></pre>

More details on arrays (and other advanced bash scripting stuff) can be found in the <a href="http://tldp.org/LDP/abs/html/" rel="nofollow noreferrer">Advanced Bash-Scripting Guide</a>.

blocks|key|358392|text|在显示bash提示符之前运行命令|type|unstyled|depth|inlineStyleRanges|entityRanges|data|358393|在"PROMPT_COMMAND“环境变量中设置一个命令，它将在每次提示之前自动运行。示例：|358394|[lsc@home]$+export+PROMPT_COMMAND="date"
Fri+Jun++5+15:19:18+BST+2009
[lsc@home]$+ls
file_a++file_b++file_c
Fri+Jun++5+15:19:19+BST+2009
[lsc@home]$+ls|code-block|syntax|javascript|358395|对于下一个愚人节的笨蛋，在某人的.bashrc中添加“导出PROMPT_COMMAND=cd”，然后坐下来观看混乱的展开。|358396|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|O|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Running a command before displaying the bash prompt

Set a command in the "PROMPT_COMMAND" env variable and it will be run automatically before each prompt.
Example:

<pre><code>[lsc@home]$ export PROMPT_COMMAND="date"
Fri Jun 5 15:19:18 BST 2009
[lsc@home]$ ls
file_a file_b file_c
Fri Jun 5 15:19:19 BST 2009
[lsc@home]$ ls
</code></pre>

For the next april fools, add "export PROMPT_COMMAND=cd" to someone's .bashrc then sit back and watch the confusion unfold.

blocks|key|3361776|text|export+TMOUT=$((15*60))|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3361777|空闲15分钟后终止bash，设置为0表示禁用。我通常将其放到我的root帐户的~/.bashrc中。它在管理你的盒子时很方便，你可能会忘记在离开终端之前注销。|3361778|entityMap^0|0|N|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|M|8|@]|D|@]|E|$]]|$1|H|3|-4|5|6|7|N|8|@]|D|@]|E|$]]]|I|$]]

<code>export TMOUT=$((15*60))</code>

Terminate bash after 15 minutes of idle time, set to 0 to disable. I usually put this to ~/.bashrc on my root accounts. It's handy when administrating your boxes and you may forget to logout before walking away from the terminal.

blocks|key|360731|text|通过设置FIGNORE变量，可以在制表符完成时忽略某些文件。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|360732|例如，如果您有一个subverion存储库，并且想要更轻松地进行导航|360733|export+FIGNORE=".svn"|code-block|syntax|javascript|360734|现在，您可以在不被.svn目录阻止的情况下使用cd。|360735|entityMap^0|4|7|0|0|0|9|4|N|2|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|T|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|U|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|V|8|@$9|W|A|X|B|C]|$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|O|3|-4|5|6|7|10|8|@]|D|@]|E|$]]]|P|$]]

You can ignore certain files while tab completing by setting th <code>FIGNORE</code> variable. 

For example, if you have a subverion repo and you want to navigate more easily do

<pre><code>export FIGNORE=".svn"
</code></pre>

now you can <code>cd</code> without being blocked by <code>.svn</code> directories.

blocks|key|3148177|text|使用算术：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3148178|if+[[+$((2%2B1))+=+$((1%2B2))+]]
++++then+echo+"still+ok"
fi|code-block|syntax|javascript|3148179|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|$]]

Using arithmetic:

<pre><code>if [[ $((2+1)) = $((1+2)) ]]
 then echo "still ok"
fi
</code></pre>

blocks|key|3361975|text|支撑扩展|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3361976|使用{x，y，z}进行标准扩展：|3361977|$+echo+foo{bar,baz,blam}
foobar+foobaz+fooblam
$+cp+program.py{,.bak}++#+very+useful+with+cp+and+mv|code-block|syntax|javascript|3361978|使用{x..y}进行序列扩展：|3361979|$+echo+{a..z}
a+b+c+d+e+f+g+h+i+j+k+l+m+n+o+p+q+r+s+t+u+v+w+x+y+z
$+echo+{a..f}{0..3}
a0+a1+a2+a3+b0+b1+b2+b3+c0+c1+c2+c3+d0+d1+d2+d3+e0+e1+e2+e3+f0+f1+f2+f3|3361980|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Brace expansion

Standard expansion with {x,y,z}:

<pre><code>$ echo foo{bar,baz,blam}
foobar foobaz fooblam
$ cp program.py{,.bak} # very useful with cp and mv
</code></pre>

Sequence expansion with {x..y}:

<pre><code>$ echo {a..z}
a b c d e f g h i j k l m n o p q r s t u v w x y z
$ echo {a..f}{0..3}
a0 a1 a2 a3 b0 b1 b2 b3 c0 c1 c2 c3 d0 d1 d2 d3 e0 e1 e2 e3 f0 f1 f2 f3
</code></pre>

blocks|key|362897|text|我最近阅读了Csh+Programming+Considered+Harmful，其中包含了这个令人惊叹的宝石：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|362898|362899|考虑管道：|blockquote|362900|362901|362902|A+%7C+B+%7C+C|code-block|syntax|javascript|362903|你想知道C的状态，这很简单:它在$中，或者在csh中是$status。但是如果你想从A那里得到它，那你就不走运了--如果你是csh的话。在Bourne+shell中，您可以获得它，尽管这样做有点棘手。下面是我不得不做的事情，我在grep+-v管道中运行dd的stderr以消除记录的输入/输出噪声，但必须返回dd的退出状态，而不是grep的退出状态：|362904|362905|device=/dev/rmt8
dd_noise='%5E[0-9]%2B\%2B[0-9]%2B+records+(in%7Cout)$'
exec+3>&1
status=`((dd+if=$device+ibs=64k+2>&1+1>&3+3>&-+4>&-;+echo+$?+>&4)+%7C
++++egrep+-v+"$dd_noise"+1>&2+3>&-+4>&-)+4>&1`
exit+$status;|362906|entityMap|0|LINK|mutability|MUTABLE|url|http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/^0|6|Y|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|11|8|@]|9|@$A|12|B|13|1|14]]|C|$]]|$1|D|3|-4|5|6|7|15|8|@]|9|@]|C|$]]|$1|E|3|F|5|G|7|16|8|@]|9|@]|C|$]]|$1|H|3|-4|5|6|7|17|8|@]|9|@]|C|$]]|$1|I|3|-4|5|6|7|18|8|@]|9|@]|C|$]]|$1|J|3|K|5|L|7|19|8|@]|9|@]|C|$M|N]]|$1|O|3|P|5|6|7|1A|8|@]|9|@]|C|$]]|$1|Q|3|-4|5|6|7|1B|8|@]|9|@]|C|$]]|$1|R|3|S|5|L|7|1C|8|@]|9|@]|C|$M|N]]|$1|T|3|-4|5|6|7|1D|8|@]|9|@]|C|$]]]|U|$V|$5|W|X|Y|C|$Z|10]]]]

I recently read <a href="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/" rel="nofollow noreferrer">Csh Programming Considered Harmful</a> which contained this astounding gem:

<blockquote>
 Consider the pipeline:
</blockquote>

<pre><code>A | B | C
</code></pre>

<blockquote>
 You want to know the status of C, well, that's easy: it's in $?, or
 $status in csh. But if you want it from A, you're out of luck -- if
 you're in the csh, that is. In the Bourne shell, you can get it, although
 doing so is a bit tricky.
 Here's something I had to do where I ran dd's
 stderr into a grep -v pipe to get rid of the records in/out noise, but had
 to return the dd's exit status, not the grep's:
</blockquote>

<pre><code>device=/dev/rmt8
dd_noise='^[0-9]+\+[0-9]+ records (in|out)$'
exec 3&gt;&amp;1
status=`((dd if=$device ibs=64k 2&gt;&amp;1 1&gt;&amp;3 3&gt;&amp;- 4&gt;&amp;-; echo $? &gt;&amp;4) |
 egrep -v "$dd_noise" 1&gt;&amp;2 3&gt;&amp;- 4&gt;&amp;-) 4&gt;&amp;1`
exit $status;
</code></pre>

blocks|key|362990|text|截断文件内容(清零文件)|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|362991|>+file|code-block|syntax|javascript|362992|具体地说，这对于截断日志文件非常有用，因为当另一个进程打开该文件时，该进程仍可能写入该文件。|362993|entityMap^0|0|C|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|S|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

Truncate content of a file (zeroing file)

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

Specifically, this is very good for truncating log files, when the file is open by another process, which still may write to the file.

blocks|key|3361795|text|这不是一个真正的特性，而是一个方向:我在commandlinefu.com上发现了许多“隐藏的特性”、秘密和各种bash有用的东西。许多评分最高的答案，我是在那个网站上学到的:)|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3361796|entityMap|0|LINK|mutability|MUTABLE|url|http://www.commandlinefu.com/^0|K|H|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

Not really a feature but rather a direction: I found many "hidden features", secrets and various bash usefulness at <a href="http://www.commandlinefu.com/" rel="nofollow noreferrer">commandlinefu.com</a>. Many of the highest rated answers to this answers, I learned them on that site :)

blocks|key|363411|text|在for+do+done中用大括号代替和loop|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|CODE|entityRanges|data|363412|For循环体通常采用do...done格式(仅举个例子)：|363413|for+f+in+*;
do
++++ls+"$f";
done|code-block|syntax|javascript|363414|但是我们可以使用C风格，使用大括号：|363415|for+f+in+*;+{
++++ls+"$f";
}|363416|我觉得这个看起来比do...done好，而且我更喜欢这个。我还没有在任何Bash文档中发现这一点，所以这实际上是一个隐藏的特性。|363417|entityMap^0|5|2|8|4|E|6|5|2|8|4|0|0|T|0|3|A|9|0|0|0|I|0|0|0|1S|9|9|0^^$0|@$1|2|3|4|5|6|7|V|8|@$9|W|A|X|B|C]|$9|Y|A|Z|B|C]|$9|10|A|11|B|C]|$9|12|A|13|B|D]|$9|14|A|15|B|D]]|E|@]|F|$]]|$1|G|3|H|5|6|7|16|8|@$9|17|A|18|B|C]|$9|19|A|1A|B|D]|$9|1B|A|1C|B|D]]|E|@]|F|$]]|$1|I|3|J|5|K|7|1D|8|@]|E|@]|F|$L|M]]|$1|N|3|O|5|6|7|1E|8|@$9|1F|A|1G|B|C]]|E|@]|F|$]]|$1|P|3|Q|5|K|7|1H|8|@]|E|@]|F|$L|M]]|$1|R|3|S|5|6|7|1I|8|@$9|1J|A|1K|B|C]|$9|1L|A|1M|B|D]]|E|@]|F|$]]|$1|T|3|-4|5|6|7|1N|8|@]|E|@]|F|$]]]|U|$]]

Braces in lieu of <code>do</code> and <code>done</code> in for loop

<code>For</code> loop body are usually in <code>do...done</code> (just an example):

<pre><code>for f in *;
do
 ls "$f";
done
</code></pre>

But we can use a C style using braces:

<pre><code>for f in *; {
 ls "$f";
}
</code></pre>

I think this looks better than <code>do...done</code>and I prefer this one. I have not yet found this in any Bash documentation, so this is really a hidden feature.

blocks|key|3148368|text|C风格的数字表达式：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3148369|let+x="RANDOM%252**8"
echo+-n+"$x+=+0b"
for+((i=8;+i>=0;+i--));+do
++let+n="2**i"
++if+((+(x&n)+==+n+));+then+echo+-n+"1"
++else+echo+-n+"0"
++fi
done
echo+""|code-block|syntax|javascript|3148370|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|$]]

C style numeric expressions:

<pre><code>let x="RANDOM%2**8"
echo -n "$x = 0b"
for ((i=8; i&gt;=0; i--)); do
 let n="2**i"
 if (( (x&amp;n) == n )); then echo -n "1"
 else echo -n "0"
 fi
done
echo ""
</code></pre>

blocks|key|3361589|text|这些属性是我的另一个最爱。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3361590|export+HISTCONTROL=erasedups
export+HISTSIZE=1000|code-block|syntax|javascript|3361591|第一个是确保bash不会将命令记录超过一次，这将真正提高history的有用性；另一个是将历史记录的大小从默认的100扩展到1000，实际上我在我的机器上将其设置为100。|offset|length|style|CODE|3361592|entityMap^0|0|0|S|7|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

These properties are another one of my favorites.

<pre><code>export HISTCONTROL=erasedups
export HISTSIZE=1000
</code></pre>

The first one makes sure bash doesn't log commands more than once, will really improves <code>history</code>'s usefulness. The other expands the history size to 1000 from the default of 100. I actually set this to 10000 on my machines.

blocks|key|3148856|text|在多个目录之间轻松移动|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3148857|这不是一个隐藏的功能，但比需要堆栈导航的pushd灵活得多。|3148858|a()+{+alias+$1=cd\+$PWD;+}|code-block|syntax|javascript|3148859|在某个地方使用cd，然后键入a+1。稍后，只需输入1就会返回到该目录。|offset|length|style|CODE|3148860|entityMap^0|0|0|0|7|2|E|3|P|1|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|R|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|T|8|@$K|U|L|V|M|N]|$K|W|L|X|M|N]|$K|Y|L|Z|M|N]]|9|@]|A|$]]|$1|O|3|-4|5|6|7|10|8|@]|9|@]|A|$]]]|P|$]]

Easily move around between multiple directories

Not a hidden feature, but much more flexible than pushd which requires stack-like navigation.

<pre><code>a() { alias $1=cd\ $PWD; }
</code></pre>

<code>cd</code> somewhere and type <code>a 1</code>. Later on just typing <code>1</code> will return to that directory.

blocks|key|360658|text|我经常使用的一个是!$来引用最后一个命令的最后一个单词：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|360659|$+less+foobar.txt
...
#+I+dont+want+that+file+any+more
$+rm+!$|code-block|syntax|javascript|360660|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|$]]

One I use a lot is !$ to refer to the last word of the last command:

<pre><code>$ less foobar.txt
...
# I dont want that file any more
$ rm !$
</code></pre>

blocks|key|3149054|text|set+-o+vi，以便对命令历史记录以及当前键入的命令进行类似vi的编辑。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3149055|entityMap^0|0|9|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

<code>set -o vi</code> in order to have vi-like editing of the command history as well as of the currently typed command.

blocks|key|363184|text|Bash具有变量间接性：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|363185|$+foo=bar
$+baz=foo
$+echo+${!baz}
bar|code-block|syntax|javascript|363186|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|$]]

Bash has variable indirection:

<pre><code>$ foo=bar
$ baz=foo
$ echo ${!baz}
bar
</code></pre>

blocks|key|358546|text|我有一个别名r='fc-s'，我发现它在一些有限的情况下非常有用。要运行最后一个命令，只需输入r并按enter，就可以了。当然，这本身并不是很有用，因为up+arrow做了同样的事情。但是您可以使用r来运行前面的命令，并进行替换。假设您的最后一个命令是一个编译某个文件的长命令：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|358547|$+gcc+-c+<file_name>.c+<lots+of+options>+-o+<file_name>.o|code-block|syntax|javascript|358548|现在，您希望使用相同的选项编译另一个文件，并拥有一个相应的.o文件：|358549|$+r+<file_name>=<new_file>|358550|会去做的。您不必使用向上箭头，导航到正确的位置，然后手动替换它们。此操作可以重复多次，因此您可以在下一步执行此操作：|358551|$+r+<new_file>=<other_file>|358552|当然，对于这样的事情，您有makefile，但我希望我已经证明了别名是有用的。|358553|我不太需要使用这个别名，但有几次我很高兴我有这个别名！|358554|entityMap^0|6|8|1B|1|2R|1|0|0|T|2|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@$9|Z|A|10|B|C]|$9|11|A|12|B|C]|$9|13|A|14|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|15|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|16|8|@$9|17|A|18|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|19|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|1A|8|@]|D|@]|E|$]]|$1|Q|3|R|5|H|7|1B|8|@]|D|@]|E|$I|J]]|$1|S|3|T|5|6|7|1C|8|@]|D|@]|E|$]]|$1|U|3|V|5|6|7|1D|8|@]|D|@]|E|$]]|$1|W|3|-4|5|6|7|1E|8|@]|D|@]|E|$]]]|X|$]]

I have an alias <code>r='fc-s'</code>, and I find it very useful in some limited cases. To run the last command, just type <code>r</code> and hit enter, and that's it. Of course, that itself is not very useful because up arrow does the same thing. But you can use <code>r</code> to run the previous command with substitutions. Let's say your last command was a long command compiling some file:

<pre><code>$ gcc -c &lt;file_name&gt;.c &lt;lots of options&gt; -o &lt;file_name&gt;.o
</code></pre>

Now you want to compile another file with the same options and have a corresponding <code>.o</code> file:

<pre><code>$ r &lt;file_name&gt;=&lt;new_file&gt;
</code></pre>

will do it. You don't have to use up arrow, navigate to the right places and then replace them each manually. This can be repeated multiple times, so you can do this next:

<pre><code>$ r &lt;new_file&gt;=&lt;other_file&gt;
</code></pre>

Of course, for such a thing you have makefiles, but I hope I have shown that the alias is useful.

I haven't needed the use of this alias a lot, but there have been times that I have been glad that I have this alias!

blocks|key|358638|text|这里字符串(<<<)。Bash手册对此进行了描述：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|358639|358640|单词被展开，并在其标准输入上提供给命令。|blockquote|358641|358642|358643|示例：|358644|$+cat<<<"$((+10*3%2B1+))+nice+isn't+it?"
31+nice+isn't+it?|code-block|syntax|javascript|358645|entityMap^0|6|3|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|X|8|@]|D|@]|E|$]]|$1|G|3|H|5|I|7|Y|8|@]|D|@]|E|$]]|$1|J|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]|$1|K|3|-4|5|6|7|10|8|@]|D|@]|E|$]]|$1|L|3|M|5|6|7|11|8|@]|D|@]|E|$]]|$1|N|3|O|5|P|7|12|8|@]|D|@]|E|$Q|R]]|$1|S|3|-4|5|6|7|13|8|@]|D|@]|E|$]]]|T|$]]

Here Strings (<code>&lt;&lt;&lt;</code>). The Bash manual gives this description:

<blockquote>
 The word is expanded and supplied to the command on its standard input.
</blockquote>

Example:

<pre><code>$ cat&lt;&lt;&lt;"$(( 10*3+1 )) nice isn't it?"
31 nice isn't it?
</code></pre>

blocks|key|3148737|text|对基本算术使用'let‘内置bash命令的|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3148738|A=10
let+B="A+*+10+%2B+1"+#+B=101
let+B="B+/+8"++++++#+B=12,+let+does+not+do+floating+point
let+B="(RANDOM+%25+6)+%2B+1"+#+B+is+now+a+random+number+between+1+and+6|code-block|syntax|javascript|3148739|要进行浮点计算，可以使用"bc“命令(bash中没有)。|offset|length|style|BOLD|3148740|FP=`echo+"scale=4;+10+/+3"+%7C+bc`+#+FP="3.3333"|3148741|entityMap^0|0|0|0|S|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|$]]

Using 'let' built-in bash command for basic arithmetic

<pre><code>A=10
let B="A * 10 + 1" # B=101
let B="B / 8" # B=12, let does not do floating point
let B="(RANDOM % 6) + 1" # B is now a random number between 1 and 6
</code></pre>

To do floating point evaluations, you can use the "bc" command (no part of bash).

<pre><code>FP=`echo "scale=4; 10 / 3" | bc` # FP="3.3333"
</code></pre>

blocks|key|360787|text|进程替换为<(cmd+...)或>(cmd+...)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|360788|在每种形式中，cmd都是在其输入或输出连接到FIFO的情况下执行的，并且在命令行上替换到该FIFO的路径：|360789|$+echo+A+file+to+read:+<(cat),+a+file+to+write+to:+>(cat)
A+file+to+read:+/dev/fd/63,+a+file+to+write+to:+/dev/fd/62|code-block|syntax|javascript|360790|例如，在不保存中间文件的情况下比较两个网站：|360791|$+diff+<(curl+-s+http://tldp.org/LDP/abs/html/)+<(curl+-s+http://www.redhat.com/mirrors/LDP/LDP/abs/html/)|360792|如果您有一个接受文件名作为输入的命令，但不接受'-‘表示标准输出，那么您可以欺骗它：|360793|$+do_thingee+--log+-
error:+can't+open+log+file:+'-'
$+do_thingee+--log+>(cat)
do_thingee+v0.2
initializing+things
processing+4+things
done|360794|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|Y|8|@]|9|@]|A|$G|H]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

Process substitution with &lt;(cmd ...) or >(cmd ...)

In each form, the cmd is executed with its input or output hooked up to a FIFO, and the path to that FIFO is substituted on the command line:

<pre class="lang-none prettyprint-override"><code>$ echo A file to read: &lt;(cat), a file to write to: &gt;(cat)
A file to read: /dev/fd/63, a file to write to: /dev/fd/62
</code></pre>

For example, to compare two website without saving intermediate files:

<pre><code>$ diff &lt;(curl -s http://tldp.org/LDP/abs/html/) &lt;(curl -s http://www.redhat.com/mirrors/LDP/LDP/abs/html/)
</code></pre>

If you have a command that takes a file name as input, but doesn't accept '-' to mean stdout, you can trick it:

<pre class="lang-none prettyprint-override"><code>$ do_thingee --log -
error: can't open log file: '-'
$ do_thingee --log &gt;(cat)
do_thingee v0.2
initializing things
processing 4 things
done
</code></pre>

blocks|key|363319|text|特殊套接字文件名:+/dev/tcp/HOST/PORT和/dev/udp/HOST/PORT|type|unstyled|depth|inlineStyleRanges|entityRanges|data|363320|从日间服务器(端口13)读取：|363321|$+cat+<+/dev/tcp/utcnist.colorado.edu/13

55786+11-08-13+03:34:21+50+0+0+172.3+UTC(NIST)+*|code-block|syntax|javascript|363322|这在与tcpserver结合使用时非常有用。|offset|length|363323|如果您不能访问wget或curl，则来自http://thesmithfam.org/blog/2006/05/23/bash-socket-programming-with-devtcp-2/的一个更高级的示例：|363324|$+exec+3<>/dev/tcp/www.google.com/80+#+hook+up+to+file+desc+3
$+echo+-e+"GET+/+HTTP/1.1\n\n"+>&3+++#+send+the+HTTP+request
$+cat+<&3++++++++++++++++++++++++++++#+read+the+HTTP+response|363325|entityMap|0|LINK|mutability|MUTABLE|url|http://cr.yp.to/ucspi-tcp/tcpserver.html|1|http://thesmithfam.org/blog/2006/05/23/bash-socket-programming-with-devtcp-2/^0|0|0|0|3|9|0|0|K|25|1|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|11|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|12|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|13|8|@]|9|@$K|14|L|15|1|16]]|A|$]]|$1|M|3|N|5|6|7|17|8|@]|9|@$K|18|L|19|1|1A]]|A|$]]|$1|O|3|P|5|F|7|1B|8|@]|9|@]|A|$G|H]]|$1|Q|3|-4|5|6|7|1C|8|@]|9|@]|A|$]]]|R|$S|$5|T|U|V|A|$W|X]]|Y|$5|T|U|V|A|$W|Z]]]]

Special socket filenames: /dev/tcp/HOST/PORT and /dev/udp/HOST/PORT

Read from a daytime server (port 13):

<pre class="lang-none prettyprint-override"><code>$ cat &lt; /dev/tcp/utcnist.colorado.edu/13

55786 11-08-13 03:34:21 50 0 0 172.3 UTC(NIST) *
</code></pre>

This can be quite useful in conjunction with <a href="http://cr.yp.to/ucspi-tcp/tcpserver.html" rel="nofollow">tcpserver</a>.

A more advanced example from <a href="http://thesmithfam.org/blog/2006/05/23/bash-socket-programming-with-devtcp-2/" rel="nofollow">http://thesmithfam.org/blog/2006/05/23/bash-socket-programming-with-devtcp-2/</a> if you don't have access to wget or curl:

<pre class="lang-none prettyprint-override"><code>$ exec 3&lt;&gt;/dev/tcp/www.google.com/80 # hook up to file desc 3
$ echo -e "GET / HTTP/1.1\n\n" &gt;&amp;3 # send the HTTP request
$ cat &lt;&amp;3 # read the HTTP response
</code></pre>

blocks|key|3361248|text|嵌入式命令替换：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3361249|3361250|主机名&+dig+%2Bshort+$(主机名)&+dig+%2Bshort+-x+$(dig+%2Bshort+$(主机名))|blockquote|3361251|3361252|3361253|此命令适用于检查邮件服务器上的RDNS。:P|3361254|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|M|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|N|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|O|8|@]|9|@]|A|$]]|$1|G|3|-4|5|6|7|P|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|Q|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|R|8|@]|9|@]|A|$]]]|K|$]]

Embedded Command substitution:

<blockquote>
 hostname &amp;&amp; dig +short $(hostname) &amp;&amp; dig +short -x $(dig +short $(hostname))
</blockquote>

This command is good for checking RDNS on your mail server. :P

blocks|key|358710|text|快速历史记录搜索|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|358711|下面给出了一个类似于历史搜索的tcsh，它既方便又简单。|358712|将以下行添加到~/.inputrc或/etc/inputrc。|CODE|358713|$+cat+~/.inputrc
"\e[A":+history-search-backward
"\e[B":+history-search-forward|code-block|syntax|javascript|358714|您可能希望使用不太偶然的组合键，如Esc+%2B+p。如果是这样的话，使用|358715|"\ep":+history-search-backward
"\en":+history-search-forward|358716|然后，只需键入前几个字母并按UpArrow键。它将显示以给定字母开头的最新命令。|358717|例如：|358718|键入grep，UpArrow。它将显示类似于grep+-ri+myText+.的内容|358719|entityMap^0|0|8|0|0|7|A|I|C|0|0|H|3|N|1|0|0|0|0|2|4|M|H|0^^$0|@$1|2|3|4|5|6|7|11|8|@$9|12|A|13|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|14|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|15|8|@$9|16|A|17|B|J]|$9|18|A|19|B|J]]|D|@]|E|$]]|$1|K|3|L|5|M|7|1A|8|@]|D|@]|E|$N|O]]|$1|P|3|Q|5|6|7|1B|8|@$9|1C|A|1D|B|J]|$9|1E|A|1F|B|J]]|D|@]|E|$]]|$1|R|3|S|5|M|7|1G|8|@]|D|@]|E|$N|O]]|$1|T|3|U|5|6|7|1H|8|@]|D|@]|E|$]]|$1|V|3|W|5|6|7|1I|8|@]|D|@]|E|$]]|$1|X|3|Y|5|6|7|1J|8|@$9|1K|A|1L|B|J]|$9|1M|A|1N|B|J]]|D|@]|E|$]]|$1|Z|3|-4|5|6|7|1O|8|@]|D|@]|E|$]]]|10|$]]

Quick History Search

Following gives a tcsh like history search which is handy and easier.

Add the following lines to <code>~/.inputrc</code> or <code>/etc/inputrc</code>.

<pre><code>$ cat ~/.inputrc
"\e[A": history-search-backward
"\e[B": history-search-forward
</code></pre>

You may want to use a less accidental key combination such as <code>Esc</code> + <code>p</code>. If that's the case, use

<pre><code>"\ep": history-search-backward
"\en": history-search-forward
</code></pre>

Then, simply type the first few letters and press UpArrow key. It'll show the most recent command that start with the given letters.

ex:

type <code>grep</code>, UpArrow.
It'll show something like <code>grep -ri myText .</code>

blocks|key|3149307|text|获取有关http://linuxconfig.net/manual-howto/key-combinations-in-bash.html中的按键组合的更多信息|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3149308|entityMap|0|LINK|mutability|MUTABLE|url|http://linuxconfig.net/manual-howto/key-combinations-in-bash.html^0|4|1T|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

Get more info about Key combinations in Bash in <a href="http://linuxconfig.net/manual-howto/key-combinations-in-bash.html" rel="nofollow">http://linuxconfig.net/manual-howto/key-combinations-in-bash.html</a>

Shell scripts are often used as glue, for automation and simple one-off tasks. What are some of your favorite "hidden" features of the Bash shell/scripting language?

<ul>
<li>One feature per answer</li>
<li>Give an example and short description of the feature, not just a link to documentation</li>
<li>Label the feature using bold title as the first line</li>
</ul>

See also:

<ul>
<li><a href="https://stackoverflow.com/questions/132241/hidden-features-of-c">Hidden features of C</a></li>
<li><a href="https://stackoverflow.com/questions/9033/hidden-features-of-c">Hidden features of C#</a></li>
<li><a href="https://stackoverflow.com/questions/75538/hidden-features-of-c">Hidden features of C++</a></li>
<li><a href="https://stackoverflow.com/questions/102254/hidden-features-of-delphi">Hidden features of Delphi</a></li>
<li><a href="https://stackoverflow.com/questions/101268/hidden-features-of-python">Hidden features of Python</a></li>
<li><a href="https://stackoverflow.com/questions/15496/hidden-features-of-java">Hidden features of Java</a></li>
<li><a href="https://stackoverflow.com/questions/61088/hidden-features-of-javascript">Hidden features of JavaScript</a></li>
<li><a href="https://stackoverflow.com/questions/63998/hidden-features-of-ruby">Hidden features of Ruby</a></li>
<li><a href="https://stackoverflow.com/questions/61401/hidden-features-of-php">Hidden features of PHP</a></li>
<li><a href="https://stackoverflow.com/questions/161872/hidden-features-of-perl">Hidden features of Perl</a></li>
<li><a href="https://stackoverflow.com/questions/102084/hidden-features-of-vbnet">Hidden features of VB.Net</a></li>
</ul>

Hidden features of Bash

Shell脚本经常被用作粘合剂，用于自动化和简单的一次性任务。您最喜欢的Bash shell/脚本语言的“隐藏”特性是什么？One feature per answer提供了该功能的示例和简短描述，而不仅仅是使用粗体标题作为第一行来显示该功能的链接另请参阅：

问Bash的隐藏功能
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回答 36

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