blocks|key|3324728|text|这也可以完成这项工作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3324729|echo+"$pid"%7Cawk+'{print+$2}'|code-block|syntax|javascript|3324730|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|$]]

This will do the job too:

<pre><code>echo "$pid"|awk '{print $2}'
</code></pre>

blocks|key|1896856|text|下面的代码应该可以工作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1896857|var="pid:+1234"
var=${var:5}|code-block|syntax|javascript|1896858|你确定bash是执行你的脚本的外壳吗？|offset|length|style|CODE|1896859|即使是与POSIX兼容的|1896860|var=${var#?????}|1896861|这比使用外部过程更可取，尽管这需要您以固定长度模式的形式对5进行硬编码。|1896862|entityMap^0|0|0|3|4|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@$I|X|J|Y|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|Z|8|@]|9|@]|A|$]]|$1|O|3|P|5|D|7|10|8|@]|9|@]|A|$E|F]]|$1|Q|3|R|5|6|7|11|8|@]|9|@]|A|$]]|$1|S|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|T|$]]

The following should work:

<pre><code>var="pid: 1234"
var=${var:5}
</code></pre>

Are you sure <code>bash</code> is the shell executing your script?

Even the POSIX-compliant

<pre><code>var=${var#?????}
</code></pre>

would be preferable to using an external process, although this requires you to hard-code the 5 in the form of a fixed-length pattern.

blocks|key|1897318|text|下面是一个使用cut(1)截取前X个字符的简明方法。此示例通过剪切从第5个字符开始的子字符串来删除前4个字符。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1897319|echo+"$pid"+%7C+cut+-c+5-|code-block|syntax|javascript|1897320|entityMap^0|7|6|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's a concise method to cut the first X characters using <code>cut(1)</code>. This example removes the first 4 characters by cutting a substring starting with 5th character.

<pre><code>echo "$pid" | cut -c 5-
</code></pre>

blocks|key|1896823|text|使用sed的-r选项(“在脚本中使用扩展正则表达式”)以使用{n}语法：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1896824|$+echo+'pid:+1234'%7C+sed+-r+'s/%5E.{5}//'
1234|code-block|syntax|javascript|1896825|entityMap^0|2|3|6|2|U|3|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]|$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|U|8|@]|D|@]|E|$]]]|L|$]]

Use the <code>-r</code> option ("use extended regular expressions in the script") to <code>sed</code> in order to use the <code>{n}</code> syntax:

<pre><code>$ echo 'pid: 1234'| sed -r 's/^.{5}//'
1234
</code></pre>

blocks|key|1897333|text|从字符串中剪切前两个字符：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1897334|$+string="1234567890";+echo+"${string:2}"
34567890|code-block|syntax|javascript|1897335|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|$]]

Cut first two characters from string:

<pre><code>$ string="1234567890"; echo "${string:2}"
34567890
</code></pre>

blocks|key|3324881|text|通过管道将其传递给awk+'{print+substr($0,42)}'，其中42比要删除的字符数多1。例如：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3324882|$+echo+abcde%7C+awk+'{print+substr($0,2)}'
bcde
$|code-block|syntax|javascript|3324883|entityMap^0|9|R|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|$]]

pipe it through <code>awk '{print substr($0,42)}'</code> where 42 is one more than the number of characters to drop. For example:

<pre><code>$ echo abcde| awk '{print substr($0,2)}'
bcde
$
</code></pre>

blocks|key|1687898|text|很有可能，您也会拥有cut。如果是这样的话：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1687899|[me@home]$+echo+"pid:+1234"+%7C+cut+-d"+"+-f2
1234|code-block|syntax|javascript|1687900|entityMap|0|LINK|mutability|MUTABLE|url|http://ss64.com/bash/cut.html^0|A|3|A|3|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@$9|V|A|W|1|X]]|E|$]]|$1|F|3|G|5|H|7|Y|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]]|L|$M|$5|N|O|P|E|$Q|R]]]]

Chances are, you'll have <a href="http://ss64.com/bash/cut.html" rel="noreferrer"><code>cut</code></a> as well. If so:

<pre><code>[me@home]$ echo "pid: 1234" | cut -d" " -f2
1234
</code></pre>

blocks|key|1688246|text|好吧，这里已经有了使用sed、awk、cut和使用bash语法的解决方案。我只想抛出另一个符合POSIX的变体：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1688247|$+echo+"pid:+1234"+%7C+tail+-c+%2B6
1234|code-block|syntax|javascript|1688248|-c告诉tail从输入数据的末尾开始计算字节偏移量，但是如果数字以%2B符号开始，则从输入数据的开始到结束。|1688249|entityMap^0|B|3|F|3|J|3|P|4|0|0|0|2|X|1|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]|$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|Y|8|@$9|Z|A|10|B|C]|$9|11|A|12|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|13|8|@]|D|@]|E|$]]]|N|$]]

Well, there have been solutions here with <code>sed</code>, <code>awk</code>, <code>cut</code> and using <code>bash</code> syntax. I just want to throw in another POSIX conform variant:

<pre><code>$ echo "pid: 1234" | tail -c +6
1234
</code></pre>

<code>-c</code> tells tail at which byte offset to start, counting from the end of the input data, yet if the the number starts with a <code>+</code> sign, it is from the beginning of the input data to the end.

blocks|key|1896944|text|另一种方式，使用cut而不是sed。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1896945|result=`echo+$pid+%7C+cut+-c+5-`|code-block|syntax|javascript|1896946|entityMap^0|8|3|E|3|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|L|$]]

Another way, using <code>cut</code> instead of <code>sed</code>.

<pre><code>result=`echo $pid | cut -c 5-`
</code></pre>

blocks|key|1897389|text|我在this+question提供的纯sed中找到了答案(诚然，是在这个问题发布之后发布的)。这完全符合您的要求，只需使用sed：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1897390|result=\`echo+"$pid"+%7C+sed+'/./+{+s/pid:\+//g;+}'\``|code-block|syntax|javascript|1897391|sed+'/./中的点)是您想要匹配的任何内容。你的问题正是我想要的，除了在我的例子中，我想要匹配文件中的特定行，然后取消注释。在我的例子中是：|style|CODE|1897392|#+Uncomment+a+line+(edit+the+file+in-place):
sed+-i+'/#\+COMMENTED_LINE_TO_MATCH/+{+s/#\+//g;+}'+/path/to/target/file|1897393|sed之后的-i将就地编辑文件(如果要在编辑文件之前测试匹配的表达式，请删除此开关)。|1897394|(我之所以发布这篇文章，是因为我想按照这个问题的要求，完全使用sed来完成这项工作，而之前的答案都没有解决这个问题。)|1897395|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/12695029/366727^0|2|D|0|0|0|0|8|0|0|0|3|6|2|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@$A|11|B|12|1|13]]|C|$]]|$1|D|3|E|5|F|7|14|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|15|8|@$A|16|B|17|K|L]]|9|@]|C|$]]|$1|M|3|N|5|F|7|18|8|@]|9|@]|C|$G|H]]|$1|O|3|P|5|6|7|19|8|@$A|1A|B|1B|K|L]|$A|1C|B|1D|K|L]]|9|@]|C|$]]|$1|Q|3|R|5|6|7|1E|8|@]|9|@]|C|$]]|$1|S|3|-4|5|6|7|1F|8|@]|9|@]|C|$]]]|T|$U|$5|V|W|X|C|$Y|Z]]]]

I found the answer in pure sed supplied by <a href="https://stackoverflow.com/a/12695029/366727">this question</a> (admittedly, posted after this question was posted). This does exactly what you asked, solely in sed:
<pre><code>result=\`echo &quot;$pid&quot; | sed '/./ { s/pid:\ //g; }'\``
</code></pre>
The dot in <code>sed '/./</code>) is whatever you want to match. Your question is exactly what I was attempting to, except in my case I wanted to match a specific line in a file and then uncomment it. In my case it was:
<pre><code># Uncomment a line (edit the file in-place):
sed -i '/#\ COMMENTED_LINE_TO_MATCH/ { s/#\ //g; }' /path/to/target/file
</code></pre>
The <code>-i</code> after <code>sed</code> is to edit the file in place (remove this switch if you want to test your matching expression prior to editing the file).
(I posted this because I wanted to do this entirely with sed as this question asked and none of the previous answered solved that problem.)

blocks|key|3412873|text|也许你可以直接提取数字，而不是从一开始删除n个字符。像这样..。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3412874|$+echo+"pid:+1234"+%7C+grep+-Po+"\d%2B"|code-block|syntax|javascript|3412875|这可能是一个更健壮的解决方案，而且看起来更直观。|3412876|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|$]]

Rather than removing n characters from the start, perhaps you could just extract the digits directly. Like so...

<pre><code>$ echo "pid: 1234" | grep -Po "\d+"
</code></pre>

This may be a more robust solution, and seems more intuitive.

I am writing shell script for embedded Linux in a small industrial box. I have a variable containing the text <code>pid: 1234</code> and I want to strip first X characters from the line, so only 1234 stays. I have more variables I need to "clean", so I need to cut away X first characters and <code>${string:5}</code> doesn't work for some reason in my system.

The only thing the box seems to have is <code>sed</code>.

I am trying to make the following to work:

<pre><code>result=$(echo "$pid" | sed 's/^.\{4\}//g')
</code></pre>

Any ideas?

How can I strip first X characters from string using sed?

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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我正在为一个小型工业设备中的嵌入式Linux编写shell脚本。我有一个包含文本pid: 1234的变量，我想去掉该行的前X个字符，所以只保留1234个字符。我有更多的变量需要“清理”，所以我需要去掉X个开头的字符，并且由于某种原因，${string:5}在我的系统中不能工作。这个盒子里唯一的东西似乎是sed。我正在尝试使以下内容生效：result=$(echo "$pid" | sed 's/^

问如何使用sed从字符串中剥离前X个字符？
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问如何使用sed从字符串中剥离前X个字符？
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