如何将bash函数的参数扩展为管道命令链？ [英] How can I expand arguments to a bash function into a chain of piped commands?

问题描述

我经常发现自己在做这样的事情很多：

I often find myself doing something like this a lot:

something | grep cat | grep bat | grep rat

当我回想起那三个单词肯定发生在某个地方， something ...的输出...现在，我可以这样做：

when all I recall is that those three words must have occurred somewhere, in some order, in the output of something...Now, i could do something like this:

something | grep '.*cat.*bat.*rat.*'

但这意味着排序之后）。因此，我正在考虑在我的环境中添加一个名为 mgrep 的bash函数，该函数将转为：

but that implies ordering (bat appears after cat). As such, I was thinking of adding a bash function to my environment called mgrep which would turn:

mgrep cat bat rat

转换为

grep cat | grep bat | grep rat

但我不太确定该怎么做（或者是否有其他选择？ ）。一个想法是循环参数，如下所示：

but I'm not quite sure how to do it (or whether there is an alternative?). One idea would be to for loop over the parameters like so:

while (($#)); do
    grep $1 some_thing > some_thing
    shift
done
cat some_thing

其中some_thing可能一些fifo，比如在bash中>（cmd）但我不确定。如何继续？

where some_thing is possibly some fifo like when one does >(cmd) in bash but I'm not sure. How would one proceed?

推荐答案

我相信你一次只能生成一条管道的命令，通过在每一步重定向标准输入。但是，将您的管道生成为字符串并使用eval执行它会更简单，更简单：

I believe you could generate a pipeline one command at a time, by redirecting stdin at each step. But it's much simpler and cleaner to generate your pipeline as a string and execute it with eval, like this:

CMD="grep '$1' "  # consume the first argument
shift

for arg in "$@"   # Add the rest in a pipeline
do
  CMD="$CMD | grep '$arg'"
done
eval $CMD

生成一个总是从标准输入中读取的greps管道，就像在你的模型中一样。请注意，它保护引用参数中的空格，以便它在写入时正常工作：

This will generate a pipeline of greps that always reads from standard input, as in your model. Note that it protects spaces in quoted arguments, so that it works correctly if you write:

mgrep 'the cat' 'the bat' 'the rat'

这篇关于如何将bash函数的参数扩展为管道命令链？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！