bash 带通配符的猫
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Cat with wildcard
提问by lorendarith
The question is maybe trivial but I can't get it to work. I just want to merge 2 particular files present in multiple specific folders into a new single file again in each specific folder.
这个问题可能是微不足道的，但我无法让它发挥作用。我只想将多个特定文件夹中存在的 2 个特定文件再次合并到每个特定文件夹中的一个新文件中。
cat */folder_*/*/file.a */folder_*/*/file.b > */folder_*/*/file.c
but it does not work 'cause
但它不起作用，因为
-bash: */folder_*/*/file.c: No such file or directory
So I thought maybe for some reason catcan't create files (though it does), so I tried
所以我想也许由于某种原因cat无法创建文件（尽管它确实如此），所以我尝试了
touch */folder_*/*/file.c; cat */folder_*/*/file.a */folder_*/*/file.b > */folder_*/*/file.c
but again it does not work with cator even touch.
但同样它不适用于cat甚至touch.
采纳答案by glenn Hymanman
for dir in */folder_*/*; do
[[ -d "$dir" ]] && ( cd "$dir" && cat file.a file.b > file.c )
done
I run the cd && catin a subshell so you don't have to cd back to where you started.
我cd && cat在一个子shell 中运行，所以你不必回到你开始的地方。
回答by Paused until further notice.
You can't use globbing for a destination file. You must fully specify the filename. It has nothing to do with catspecifically.
您不能对目标文件使用通配符。您必须完全指定文件名。它与cat具体无关。
回答by tripleee
Maybe you want something like this;
也许你想要这样的东西；
for a in */folder_*/*/file.a; do
# maybe continue if b missing
cat "$a" "${a%.a}.b" >"${a%.a}.c"
done
Wildcards and redirections are processed by the shell; cathas no concept of wildcards, nor does it know where you are sending its output.
通配符和重定向由 shell 处理；cat没有通配符的概念，也不知道您将其输出发送到哪里。
