Find files of specific file types using shell script

Question

I have a requirement to recursively loop through all the files of certain file types in a directory. The file types is an array variable containing the list of file types that we need to go through for processing. The array values are actually dynamically populated. For the sake of simplicity I am declaring a static array.

 declare -a arr=("pdf" "doc" "txt")

I have the following code to recursively list all the files in the directory, but I am not able to figure out how include the array "arr" to only get back those file types that are included in the array.

find $i -type f -print0 | while read -d $'\0' file; do
    echo $file;
    #Process file
done

Please help me modify the code so that I could retrieve the specified file types only and not all files.

This question on the Superuser SE site may be of help.

Mike Holt
– Mike Holt

2017-07-21 23:11:41 +00:00
Commented Jul 21, 2017 at 23:11 — Mike Holt
– Mike Holt, Commented Jul 21, 2017 at 23:11

janos · Accepted Answer · 2017-07-21 23:59:35Z

5

I assume that by file types "pdf", "doc", "txt", you mean filenames with those extensions.

If the number of file types is reasonably small (less than a few dozen), then you could build an array of arguments to pass to find in the format:

... -name '*.pdf' -o -name '*.doc' -o -name '*.txt' ...

Assuming that the array of file types is not empty, here's one way to do it (thanks @mike-holt):

arr=(pdf doc txt)

findargs=()

for t in "${arr[@]}"; do
    findargs+=(-name "*.$t" -o)
done

find . -type f \( "${findargs[@]}" -false \)

edited Jul 21, 2017 at 23:59

answered Jul 21, 2017 at 23:53

janos

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1 Comment

David C. Rankin Over a year ago

I like that way too.

David C. Rankin · Accepted Answer · 2017-07-21 23:50:27Z

4

What you will need to do is dynamically build a regex from your array of types (presuming extensions) to pass to find with the -regex option. find can then use the regex to find filenames that match. Given your example, you are wanting to build a regex similar to:

"^.*[.]\(pdf\|doc\|txt\)$"

In order to build that regex dynamically from the array content, you can do something similar to the following

#!/bin/bash

arr=(pdf doc txt)   ## dynamically built array of extensions
n=${#arr[@]}        ## number of elements in array
regex='^.*[.]\('    ## beginning of regex
srch="${1:-.}"      ## path to search (default '.')

for ((i = 0; i < $n; i++)); do  ## loop over each element
    ## if not last, add "${arr[i]}\|" otherwise add "${arr[i]}\)"
    ((i < n - 1)) && regex="$regex${arr[i]}\|" || regex="$regex${arr[i]}\)"
done

regex="$regex\$"    ## add the final '$'

find "$srch" -type f -regex "$regex"  ## execute the find

(note this uses a bash specific C-style for loop and arrays so it is not POSIX shell portable -- which since you are using an array shouldn't be a problem)

Give it a try and let me know if that meets your needs.

answered Jul 21, 2017 at 23:50

David C. Rankin

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4 Comments

Mike Holt Over a year ago

Or you could just do find $ $(printf -- "-name *.%s -o " "${arr[@]}") -false $

David C. Rankin Over a year ago

Yes, that looks like an easier approach using -name and -o as @janos answered with. I took the Rube Goldberg regex approach :)

janos Over a year ago

@MikeHolt the * may get expanded by the shell. It's not very safe. But I got a tip from you in -false and greatly improved my answer with it, thanks!

Mike Holt Over a year ago

@janos Hmm. Seems you're right. It fails if any of the types in arr are present in the top-level directory. So yeah, you'd either have to construct an array of arguments as in your answer, or use set -o noglob first. I'm just a sucker for one-liners. :-)

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