脚本:只变换很长的行

脚本:只变换很长的行

 

比如，要快速的扫描一个文件，看看哪些行过长:

 

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awk '{if (length($0) > 72) {print $0}}'  filename

   还有一个有趣点的方法，就是使用shell中的$#vamname结构，它会返回任意一个替换了vamname的变量的长度(指内容，不是变量名)。

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#!/bin/sh

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# toolong.sh -- 使用fmt.sh格式化那些超过指定长度的长行

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width=72

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if [ ! -r "$1" ]; then

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    echo "Usage: `basename $0` filename" >&2

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    exit 1

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fi

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while read input

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do

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    if [ ${#input} -gt $width ]; then

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        echo "$input" | fmt.sh

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    else

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        echo "$input"

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    fi

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done < $1

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exit 0

   这个脚本中处理输入文件的方法很有意思。首先用一个简单的 <$1 达到输入文件的目的，然后用一个 read input 将每行都解析下。 

   如果你的shell环境中没有 ${#var} 记法的话，可以使用如下方法代替： 

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varlength="$(echo "$var" | wc -c)"

但是，wc命令有一个十分让人生厌的特性，它的输出会有一个前导空格，目的是让输出列表排列的漂亮些。为了回避这个讨厌的问题，会有一个微小的改动，就是在通过最后一个管道时，只允许数字通过：[注: 在我的Linux中，没发现作者说的这个特性，并且使用了sed后，可能会有问题，需读者在自己的环境中检验]

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varlength="$(echo "$var" | wc -c | sed 's/[^:digit:]//')"

运行结果：

 

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$ toolong ragged.txt

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So she sat on, with closed eyes, and half believed herself in

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Wonderland, though she knew she had but to open them again, and

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all would change to dull reality--the grass would be only rustling

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in the wind, and the pool rippling to the waving of the reeds--the

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rattling teacups would change to tinkling sheep-bells, and the

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Queen's shrill cries to the voice of the shepherd boy--and the

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sneeze

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of the baby, the shriek of the Gryphon, and all the other queer

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noises, would change (she knew) to the confused clamour of the busy

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farm-yard--while the lowing of the cattle in the distance would

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take the place of the Mock Turtle's heavy sobs.

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Notice that, unlike a standard invocation of fmt, toolong has retained line breaks where possible, so the word "sneeze," 

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which is on a line by itself in the input file, is also on a line by itself in the output.