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I need to find a list of files in multiple subdirectories and save the path of each file in a txt file. I have all the filenames in a list in filenames.txt. I am trying to do this:

while read -r fname; do
    find . -name "$fname" > paths.txt
done < filenames.txt

Is this correct? It seems to take quite more time than I was expecting, even though I know I have a lot of subdirectories (200k) to search. Are there better ways of doing this? Thanks

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  • Filenames may contain newline characters. Can we assume that none of your filenames contain newline characters? – Quasímodo Jun 30 '20 at 22:34
  • @Quasimodo each filename is on a new line. I don't know if this means that there is a newline character after each filename, but I suppose so. How can I check? – ginopino Jun 30 '20 at 22:56
  • That is what I meant, filenames with no newline, but after each filename a newline. (TBH I think it would be impossible to have filenames in a text file if we allowed all the unusual but allowed characters to be part of the filenames.) Thanks for the clarification. – Quasímodo Jun 30 '20 at 23:00
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You are running find multiple times, once for each line in filenames.txt - that can be the bottleneck.

You can try to reverse the process - first find all files, then compare it to the files from the list. Something like

find * > allfiles.txt
grep -f filenames.txt allfiles.txt
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  • find * will not output any files that start with a . such as .ssh – fpmurphy Jul 1 '20 at 15:40
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You could do something like:

find . -print0 | gawk -F/ '
   ARGIND == 1 {selected[$0]; next}
   $NF in selected' filenames.txt RS='\0' -

That is, have find reports all the files, but do the filtering with gawk using a hash table built from the contents of filenames.txt.

That way, you run find only once and do the matching in a more efficient manner.

That assumes filenames.txt is meant to contain a list of literal filenames, not a list of wildcard patterns (find's -name expects a wildcard pattern, not a literal filename).

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