Pipelining and xargs

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I am trying to delete some .class file from a directory. So first I have tired to count the available .class file using the following command (after going to the directory) – 

$ find . -name *.class | wc -l

Here I can understand the role of pipelining (|) – the output of the find command/process works as a input of wc command (please correct me If I am wrong). The above command works fine for me and produce the correct output. But when I am trying to delete the all .class files using the following command with pipelining – 

$ find . -name *.class | rm *  # case-1

then it doesn’t works. It shows the following error – 

rm: cannot remove `<a_directory_name>': Is a directory
rm: cannot remove `<an_another_directory_name>': Is a directory

But when I use xargs then it works fine – 

$ find . -name *.class | xargs rm *  # case-2

Now my question is can anyone tell me why case-1 doesn’t works while the case-2 works fine?.

Thanks in advance.

Answer

The reason that Case-1 does not work is that rm does not take the arguments via STDIN, it takes the arguments or the files to remove as:

rm file_1 file_2

Whereas in Case-2 xargs takes the output of the find command via STDIN and converts the filenames as arguments for the rm command.

Please read man rm and man xargs to get more idea on this.

Attribution
Source : Link , Question Author : Razib , Answer Author : heemayl

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