while loop - done < command instead of done < file

Question

For moving all files in sub folders into the current folder I use this script

while read f
do
    mv "$f" .
done < file_list

this works great but i have to generate the file_list with

find . -name *.avi > file_list

what i want is to add the command directly to my while loop

while read f
do
    mv "$f" .
done < find . -name *.avi

but bash tells me -bash: syntax error near unexpected token `.'

What is an easy solution to pipe the find command into my while loop?

Answer 1

You don't need any loop here, find can do it for you:

find . -name '*.avi' -exec mv {} . \;

Answer 2

You can also use process substitution.

while IFS= read -r f
do
    mv -- "$f" .
done < <(find . -name '*.avi' )

In shells like bash, compared to the pipe approach, it has the advantage of not running the loop in a subshell, so the variable assignments you would do in the loop for instance are not lost afterwards. In bash (or zsh), you'd rather do:

while IFS= read <&3 -rd '' f 
do
    mv -- "$f" .
done 3< <(find . -name '*.avi' -print0)

using NUL delimiters to be able to work with arbitrary file names, using fd 3 instead of 0 as mv may prompt the user and would read the answer on stdin which would be the output of find if you used 0.

Or using the find command itself

find . -name '*.avi' -exec mv -t . {} +

Using + means we pass many arguments at a time to mv which saves having to run one mv invocation per file. -t is a GNU extension. With other mv implementations, you can change it to:

find . -name '*.avi' -exec sh -c 'exec mv "$@" .' sh {} +

Answer 3

proper way to do this is pipe

find . -name '*.avi' |
while read f
do
    mv "$f" .
done 

the result from first command "find . -name *.avi" will feed the second.

This is call a pipe (from the symbol | ). You can think of pipe as a temporary file like

find . -name '*.avi' > file1.tmp
while read f
do
    mv "$f" .
done < file1.tmp
rm file1.tmp

---

As pointed out filename with space or newline are likely to cause error.

If the only purpose is to move file, use @Terdon's commands.

Also you must quote *.avi or it will break on second run.

find: paths must precede expression: `foo.avi' 
find: possible unquoted pattern after predicate `-name'?

Answer 4

A halfway position between the two existing answers is to "inline" the find and use a for loop.

for f in `find . -name '*.avi' `
do
    mv "$f" .
done 

The back-ticks are what make the find command execute in place and then its output is substituted.

Downside is spaces and unexpected weird characters in filenames can cause issues. The answer by @Terdon is superior.