使用awk从stdin或文件中读取 [英] Reading from stdin OR file using awk

问题描述

所以这是到目前为止的代码:

So here's my code so far:

awk '{++a[length()]} END{for (i in a) print i, a[i]}' <$1 | sort -n

从文本文件中读取行的长度，然后输出行的长度，然后输出多少行具有相同的长度.

which reads the lengths of lines from a text file, and outputs the length of the line, and then how many lines have the same length.

所以输入:

hello
guys
hows
it
going

将输出:

2 1
4 2
5 2

我希望它也能够具有stdin，因此我将能够运行命令"./script filename.txt"，也能够使用标准输入来运行该命令.

I want it to be able to have stdin too, so i will be able to run the command "./script filename.txt" and also be able to run the command using standard input.

有什么方法可以通过while循环完成吗?我试图做类似的事情:

Is there any way this can be done with a while loop? I have tried to do something similar to:

while read line
do
    awk '{++a[length()]} END{for (i in a) print i, a[i]}' <${1:-/dev/stdin} | sort -n
done <${1:-/dev/stdin}

但似乎什么都无法正常工作...

but nothing seems to be working correctly...

有什么想法吗?

推荐答案

您可以使用破折号(-)作为文件名，awk将其理解为使用stdin作为要解析的文件.例如:

You may use the dash (-) as the filename, awk understands it as using stdin as the file to parse. For example:

awk '{++a[length()]} END{for (i in a) print i, a[i]}' -

另外，通过完全不指定文件名，awk也使用标准输入

Also, by not specifying a filename at all, awk also uses stdin

awk '{++a[length()]} END{for (i in a) print i, a[i]}'

请注意，您可以将它们混合使用.以下将按此顺序处理file1.txt，stdin和file2.txt:

And note that you can mix them both. The following will process file1.txt, stdin and file2.txt in that order:

awk '{++a[length()]} END{for (i in a) print i, a[i]}' file1.txt - file2.txt

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