有人可以在本bash末尾解释符号的内部工作原理:"_ {} \;" [英] Can someone explain the inner working of the symbols at the end of this bash: “_ {} \;”

问题描述

我在shell中运行了以下命令，将.HEIC文件批量转换为.JPG文件，该命令成功，但是有一部分我不理解:

I ran the following command in shell to batch convert .HEIC files to .JPG files, the command is successful, however there's a part of it I don't understand:

find . -name '*.HEIC' -exec sh -c 'magick convert $1 "${1%.HEIC}.JPG"' _ {} \;

显然，_ {}用于将find结果分配给$1，但是如何?我在Google或这里都找不到解释，并且man find没有运气.答案很可能在这里，但是这些符号并不是很好地搜索.

Apparently _ {} acts to assign find result to $1, but how? I can't find an explanation on google nor here, and didn't have any luck with man find. It's entirely possible that answers were here but these symbols are not very nice to search for.

所以问题是，_ {}如何将变量分配给$1?是否可以使用find/或其他命令为其分配多个变量?

So the question is, how does _ {} assign variable to $1? Is it possible to assign multiple variable to it with find/ or other commands?

推荐答案

_ {}如何将文件名分配给$1涉及两件事.首先，是find的-exec的工作方式:它作为命令运行以下参数(直至转义的;)，但将{}替换为找到的文件的路径.因此，如果找到./somefile.HEIC，它将运行与命令等效的命令:

There are two things involved in how _ {} assigns the filename to $1. First, is how the find's -exec works: it runs the following arguments (up to the escaped ;) as a command, but with {} replaced with the path to the file it found. Thus, if it finds ./somefile.HEIC, it'll run the equivalent of the command:

sh -c 'magick convert $1 "${1%.HEIC}.JPG"' _ ./somefile.HEIC

第二部分是sh命令. sh可以做很多事情，但是如果给它一个-c选项，它将紧随其后的参数(magick convert $1 "${1%.HEIC}.JPG")作为要解析和运行的命令字符串，有点像一个迷你脚本.之后的参数将作为该小型脚本的参数，以$0开头.在这种情况下，这意味着它将在$0设置为_且$1设置为"./somefile.HEIC"的情况下运行小型脚本.如果提供了更多参数，则为$2，$3等.

The second part is the sh command. sh can do a number of things, but if it's given a -c option, it takes the immediately following argument (magick convert $1 "${1%.HEIC}.JPG") as a command string to parse and run, sort of like a little mini-script. The arguments after that are taken as arguments to that mini-script, starting with $0. In this case, that means it runs the mini-script with $0 set to _, and $1 set to "./somefile.HEIC". If more arguments were supplied, they'd be $2, $3, etc.

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