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通过管道读取文件

tag-icon • tag-icon shell-script pipe
通过管道读取文件

我编写了一个示例代码，用于使用互联网上的 hack 来读取文件的内容并维护行尾格式。我将 shell 文件称为“pipeTesting”，将文本文件称为“textExample”。如果我将该文件作为 shell 脚本的参数调用，“pipeTesting”就会起作用。

然而，在某些情况下，文件是通过管道检索的；如果我使用命令向 pipelineTesting 提供文本cat，则根本没有参数，因为echo $@不打印任何内容。需要注意的是，我必须-p /dev/stdin创建一个用于管道使用的案例和一个用于参数使用的案例。

有没有办法在管道的情况下显示文件的内容并保持行尾？

谢谢。

代码看起来像这样：

#!/bin/bash

if [ -p /dev/stdin ]; then
    echo $@
else
    while read
    do
        echo $REPLY
    done < $1
fi
exit 0

其应用是：

$ cat textExample.txt
Much I marvelled this ungainly fowl to hear discourse so plainly,
Though its answer little meaning- little relevancy bore;
For we cannot help agreeing that no living human being
Ever yet was blessed with seeing bird above his chamber door-
Bird or beast upon the sculptured bust above his chamber door,
With such name as "Nevermore."
$ pipeTester textExample.txt 
Much I marvelled this ungainly fowl to hear discourse so plainly,
Though its answer little meaning- little relevancy bore;
For we cannot help agreeing that no living human being
Ever yet was blessed with seeing bird above his chamber door-
Bird or beast upon the sculptured bust above his chamber door,
With such name as "Nevermore."
$ cat textExample.txt | pipeTester 
_

答案1

#!/bin/sh

infile=${1--}

cat "$infile"

也就是说，将infile变量设置为第一个参数的名称，但如果该名称不可用，请将其设置为-. cat作为-输入文件名将从标准输入（即从管道或重定向）读取。

较短：

#!/bin/sh

cat -- "${1--}"

或者，正如斯特凡指出的那样，

cat -- "$@"

这还允许您在命令行上给出多个文件名。

还更短：

alias PipeTester=cat

您所做的或多或少是重新实现cat.PipeTester事实上，您的脚本可能会被替换cat，上面的脚本是通过别名来实现的。

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