How to execute "mv" command with conditions - move files with certain ending to other folder

Question

I am a computer science student. Second year of school - and I'm learning about Linux. Because of the Corona virus, I study in an independent way. During my studies I came across a question with a number of sections - I can't solve it.

The question wants me to execute the mv command - that I transfer some files to the folder. I tried to execute the mv command - and tried to integrate "pipe" or other commands like find.

This is not a normal mv command in my opinion, more things need to be integrated, how I can't decipher it. I tried to solve the question for a few days. I also tried to find such identical questions in the forum - but I couldn't find them.

The question:

1. Write one command that will copy all files ending in .c or .h into the Programs folder.

My try was maybe do that:

find "*.c" -o "*.h" | mv Programs

Answer 1

The assignment can be interpreted in three ways:

1. Copy all .c and .h files from the current directory to the directory Programs, or
2. Copy all .c and .h files from the current directory or anywhere below it to the directory Programs.
3. Copy all accessible .c and .h from anywhere on the system to the directory Programs.

Note that the assignment says "copy", not "move". This means that you should be using the cp command, not mv.

The first interpretation of the assignment is solved by

cp *.[ch] Programs

(assuming that *.[ch] matches all files we're interested in, and there's not many thousands of these in the current directory).

The second interpretation of the assignment is solved by

find . -path ./Programs -prune -o -type f -name '*.[ch]' -exec cp {} Programs \;

This searches for all regular files with a .c or .h filename suffix in or below the current directory, and executes cp for each such file. We can't pipe to cp since that utility does not read its standard input stream.

We also make sure to avoid looking inside the Programs directory (assumed to be a subdirectory in the current directory). Not doing that would end up copying files from Programs into Programs. See "Explain find's -path and -prune options" for more info about -path and -prune.

The third interpretation is easy to implement from the second:

find / -path "$PWD/Programs" -prune -o -type f -name '*.[ch]' -exec cp {} Programs \;

... we just need find to start at the top of the directory tree and to specify that the Programs directory to avoid is the one at the path $PWD/Programs.

This will likely throw a number of errors at you due to you not having access everywhere. To avoid this, also prune directories that you can't access and only copy files that you can read:

find / \( -type d ! -executable -o -path "$PWD/Programs" \) -prune -o \
    -type f -name '*.[ch]' -readable -exec cp {} Programs \;

This requires GNU find for the -executable test (a directory is searchable if it's executable) and the -readable test.

Note that the find variations here will restrict the files to only regular files (through the -type f test), while the cp *.[ch] approach would copy any type of thing that ends in those two characters. Also, the find solution would copy hidden files (files with names that begin with a dot), while the first solution would not match those types of names by default.