为什么我的 find 和 xargs 复制命令适用于一个文件夹而不适用于另一个文件夹？

Question

I have two directories, x86_64 and i386 . I want to filter out test RPMS from both of these folders and place them in a seperate one; test_release/{version}-x86_64/x86_64 and test_release/{version}-i386/i386 , respectively.

So my first command works fine:

find x86_64/ -type f -name '*test*' -o -name '*demo*' -o -name '*log*' |
xargs cp -rt test_release/${RELEASE}-x86_64/x86_64

My second command is exactly the same, except with different folder names:

find i386/ -type f -name '*test*' -o -name '*demo*' -o -name '*log*' |
xargs cp -rt test_release/${RELEASE}-i386/i386

Only the second command gives me the error:

cp: missing file operand

Am I missing something?

Answer 1

The error happens because your find command doesn't return any files. Disappointingly, xargs still runs cp , but ends up calling it with too few arguments; and so you get the error message.

GNU xargs has an -r option which solves this specific case; but a more portable and more robust solution is to use find -exec .

find i386/ -type f -name '*test*' -o -name '*demo*' -o -name '*log*' \
    -exec cp -rt "test_release/${RELEASE}-i386/i386" {} +

The + statement terminator for -exec is not entirely portable, but if you have cp -t I guess you're on Linux, or at least are using a recent find (GNU or not GNU. If not, replacing + with \; is a workaround, though it will end up running more processes than the equivalent xargs construct).