Bash Shell(字符串)操作小结

小鱼儿 2022-06-10 00:25 280阅读 0赞

基本下面引用的文章，加了几项, 做个记录，懒得记了，也省得每次Google。

[http://my.oschina.net/aiguozhe/blog/41557][http_my.oschina.net_aiguozhe_blog_41557]

1. 取长度

<table> 
 <tbody> 
  <tr> 
   <td> <p>2</p> </td> 
   <td> <p><span>expr</span> length $str&nbsp;&nbsp; <span># 4</span></p> </td> 
  </tr> 
 </tbody> 
</table>

好像一般使用第二种

2. 查找子串的位置

<table> 
 <tbody> 
  <tr> 
   <td> <p>2</p> </td> 
   <td> <p><span>expr</span> index $str <span>"a"</span>&nbsp; <span># 1</span></p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>3</p> </td> 
   <td> <p><span>expr</span> index $str <span>"b"</span>&nbsp; <span># 2</span></p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>4</p> </td> 
   <td> <p><span>expr</span> index $str <span>"x"</span>&nbsp; <span># 0</span></p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>5</p> </td> 
   <td> <p><span>expr</span> index $str <span>""</span>&nbsp;&nbsp; <span># 0</span></p> </td> 
  </tr> 
 </tbody> 
</table>

3. 选取子串

<table> 
 <tbody> 
  <tr> 
   <td> <p>1</p> </td> 
   <td> <p><span>str=</span>"abcdef"</p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>2</p> </td> 
   <td> <p><span>expr</span><span> substr </span><span>"$str"</span><span> 1 3&nbsp; </span># <span>从第一个位置开始取</span>3<span>个字符，</span> abc</p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>3</p> </td> 
   <td> <p><span>expr</span><span> substr </span><span>"$str"</span><span> 2 5&nbsp; </span># <span>从第二个位置开始取</span>5<span>个字符，</span> bcdef</p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>4</p> </td> 
   <td> <p><span>expr</span><span> substr </span><span>"$str"</span><span> 4 5&nbsp; </span># <span>从第四个位置开始取</span>5<span>个字符，</span> def</p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>6</p> </td> 
   <td> <p><span>echo</span><span> ${str:2}&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span> # <span>从第二个位置开始提取字符串，</span> bcdef</p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>7</p> </td> 
   <td> <p><span>echo</span><span> ${str:2:3}&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span> # <span>从第二个位置开始提取</span>3<span>个字符</span>, bcd</p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>8</p> </td> 
   <td> <p><span>echo</span><span> ${str:(-2)}&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span> # <span>从倒数第二个位置向左提取字符串</span>, abcde</p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>9</p> </td> 
   <td> <p><span>echo</span><span> ${str:(-2):3}&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span> # <span>从倒数第二个位置向左提取</span>6<span>个字符</span>, cde</p> </td> 
  </tr> 
 </tbody> 
</table>

4. 截取子串

<table> 
 <tbody> 
  <tr> 
   <td> <p>01</p> </td> 
   <td> <p><span>str=</span>"abbc,def,ghi,abcjkl"</p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>02</p> </td> 
   <td> <p><span>echo</span><span> ${str</span>#a*c}&nbsp;&nbsp;&nbsp;&nbsp; # ,def,ghi,abcjkl&nbsp; <span>一个井号</span>(#) <span>表示从左边截取最短的匹配</span></p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>03</p> </td> 
   <td> <p><span>echo</span><span> ${str</span>##a*c}&nbsp;&nbsp;&nbsp; # jkl<span>，</span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <span>两个井号</span>(##) <span>表示从左边截取最长的匹配</span></p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>04</p> </td> 
   <td> <p><span>echo</span><span> ${str</span>#"a*c"}&nbsp;&nbsp; # <span>空</span>,<span>因为</span>str<span>中没有子串</span>"a*c"</p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>06</p> </td> 
   <td> <p><span>echo</span><span> ${str</span>#d*f)&nbsp;&nbsp;&nbsp;&nbsp; # abbc,def,ghi,abcjkl,</p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>07</p> </td> 
   <td> <p><span>echo</span><span> ${str</span>#*d*f}&nbsp;&nbsp;&nbsp; # ,ghi,abcjkl&nbsp;&nbsp;</p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>09</p> </td> 
   <td> <p><span>echo</span><span> ${str%a*l}&nbsp;&nbsp;&nbsp;&nbsp; </span> # abbc,def,ghi&nbsp; <span>一个百分号</span>(%)<span>表示从右边截取最短的匹配</span></p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>10</p> </td> 
   <td> <p><span>echo</span><span> ${str%%b*l}&nbsp;&nbsp;&nbsp; </span> # a&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <span>两个百分号表示</span>(%%)<span>表示从右边截取最长的匹配</span></p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>11</p> </td> 
   <td> <p><span>echo</span><span> ${str%a*c}&nbsp;&nbsp;&nbsp;&nbsp; </span> # abbc,def,ghi,abcjkl</p> </td> 
  </tr> 
 </tbody> 
</table>

可以这样记忆, 井号（\#）通常用于表示一个数字，它是放在前面的；百分号（%）卸载数字的后面; 或者这样记忆，在键盘布局中，井号(\#)总是位于百分号（%）的左边(即前面)    :-)

5. 字符串替换

<table> 
 <tbody> 
  <tr> 
   <td> <p>1</p> </td> 
   <td> <p><span>str=</span>"apple, tree, apple tree"</p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>2</p> </td> 
   <td> <p><span>echo</span> ${str/apple/APPLE}&nbsp;&nbsp; <span> # </span><span>替换第一次出现的</span><span>apple</span></p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>3</p> </td> 
   <td> <p><span>echo</span> ${str//apple/APPLE}&nbsp; <span> # </span><span>替换所有</span><span>apple</span></p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>5</p> </td> 
   <td> <p><span>echo</span><span> ${str/</span>#apple/APPLE}&nbsp; # <span>如果字符串</span>str<span>以</span>apple<span>开头，则用</span>APPLE<span>替换它</span></p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>6</p> </td> 
   <td> <p><span>echo</span><span> ${str/%apple/APPLE}&nbsp; </span> # <span>如果字符串</span>str<span>以</span>apple<span>结尾，则用</span>APPLE<span>替换它</span></p> </td> 
  </tr> 
 </tbody> 
</table>

6. 比较

\*单组\[\]是可以的。

<table> 
 <tbody> 
  <tr> 
   <td> <p>1</p> </td> 
   <td> <p><span>[[ </span><span>"a.txt"</span><span> == a* ]]&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span># <span>逻辑真</span> (pattern matching)</p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>2</p> </td> 
   <td> <p><span>[[ </span><span>"a.txt"</span><span> =~ .*\.txt ]]&nbsp;&nbsp; </span># <span>逻辑真</span> (regex matching)</p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>3</p> </td> 
   <td> <p><span>[[ </span><span>"abc"</span><span> == </span><span>"abc"</span><span> ]]&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span># <span> 逻辑真</span> (string comparision)</p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>4</p> </td> 
   <td> <p><span>[[ </span><span>"11"</span><span> &lt; </span><span>"2"</span><span> ]]&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span># <span> 逻辑真</span> (string comparision), <span>按</span>ascii<span>值比较</span></p> </td> 
  </tr> 
 </tbody> 
</table>

7. 连接

<table> 
 <tbody> 
  <tr> 
   <td> <p>1</p> </td> 
   <td> <p><span>s1=</span>"hello"</p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>2</p> </td> 
   <td> <p><span>s2=</span>"world"</p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>3</p> </td> 
   <td> <p><span>echo</span><span> ${s1}${s2}&nbsp;&nbsp; </span># <span>当然这样写</span> $s1$s2 <span>也行，但最好加上大括号</span></p> </td> 
  </tr> 
 </tbody> 
</table>

**8. 在变量中保存指令执行的结果**

<table> 
 <tbody> 
  <tr> 
   <td> <p>1</p> </td> 
   <td> <p>platform=`uname -p`</p> </td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <td> <p>2</p> </td> 
   <td> <p>currentPath=`pwd`</p> </td> 
  </tr> 
 </tbody> 
</table>

** \*注意两边不是单引号。**

**9. 分割字串到一个数组中**

<table> 
 <tbody> 
  <tr> 
   <td> <p>1</p> </td> 
   <td> <p>arguments=($(<span>echo</span> ${x} | <span>tr</span> <span>"," "\n"</span>)) <span><strong>#x为传入参数，以逗号分隔</strong></span></p> </td> 
  </tr> 
 </tbody> 
</table>

**10. 大小写转换**

**debPackName=\`****echo $2|awk '\{print tolower($0)\}'****\` ** **\#转为小写**

**debPackName=\`****echo $2|awk '\{print toupper($0)\}'****\`** **\#转为大写**

[http_my.oschina.net_aiguozhe_blog_41557]: http://my.oschina.net/aiguozhe/blog/41557