显示带有行号的文件

显示带有行号的文件

 

  有许多种方法可以达到显示行号的目的，某些程序甚至很简短。比如可以用一个awk来实现： 

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awk '{print NR": "$0}' < inputfile

   同样，在某些Unix版本上，cat命令有-n选项，或是more(less, pg)也有能显示行号的选项。但还有一些Unix的版本上，可能这些都统统没有，那么此时，下面的这个简易脚本就可以发威了：

 

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#!/bin/sh

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# numberlines.sh -- 效果等同于cat -n命令

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for filename

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do

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    linecount="1"

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    while read line

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    do

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        echo "${linecount}: $line"

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        linecount="$(($linecount+1))"

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    done < $filename

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done

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exit 0

   这个脚本可以接受任意多的文件作为输入，但是不能通过管道给它提供输入。当然，若有需要可以修改下程序。 

测试下脚本： 

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$ numberlines text.snippet.txt

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1: Perhaps one of the most valuable uses of shell scripts is to fix

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2: your particular flavor of Unix and make it more like other flavors,

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3: to bring your commands into conformance or to increase consistency

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4: across different systems. The outsider view of Unix suggests a

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5: nice, uniform command-line experience, helped along by the existence

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6: of and compliance with the POSIX standards for Unix. But anyone who's

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7: ever touched more than one computer knows how much they can vary

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8: within these broad parameters.

如果你有了一个标记出行号的文件，那么此时你就可以反转文件了： 

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cat -n filename | sort -nr | cut -c8-

上面的这行命令什么时候会很有用呢？一个经常遇到的情况就是，你想显示一个日志文件的时候.