A script that iterates over all files in folder - shell

Question

There is a script on a server that I need to run over all the files in a folder. To run this script over one file I use this shell script:
for input in /home/arashsa/duo-bokmaal/Bokmaal/DUO_BM_28042.txt ; do
name=$(basename "$input")
/corpora/bokm/tools/The-Oslo-Bergen-Tagger/./tag-lbk.sh "$input" > "/home/arashsa/duo-bokmaal-obt/$name"
done
I'm terrible at writing shell scripts, and have not managed to found out how to iterate over files. What I want it is to make the script iterate over all files in a given folder that end with .txt and not those that end with _metadata.txt. So I'm thinking I would give it the folder path as argument, make it iterate over all the files in that folder, and run script on files ending with .txt and not _metadata.txt

Answer 1

Use find and the exec option.
$ find /path/to/dir -exec <command here> \;
Each file or directory can be obtained by using {}.
Example usage: $ find . -exec echo {} \;, this will echo each file name recursively or directory name in the current directory. You can use some other options to further specify the desired files and directories you wish to handle. I will briefly explain some of them. Note that the echo is redundant because the output of find will automatically print but I'll leave it there to illustrate the working of exec. This being said, following commands yield the same result: $ find . -exec echo {} \; and $ find .
maxdepth and mindepth
Specifying the maxdepth and mindepth allows you to go as deep down the directory structure as you like. Maxdepth determines how many times find will enter a directory and mindepth determines how many times a directory should be entered before selecting a file or dir.
Example usages:
(1) listing only elements from this dir, including . (= current dir).
(2) listing only elements from current dir excluding .
(3) listing elements from root dir and all dirs in this dir
(1)$ find . -maxdepth 1 -exec echo {} \;
(2)$ find . -mindepth 1 -maxdepth 1 -exec echo {} \;
# or, alternatively
(2)$ find . ! -path . -maxdepth 1 -exec echo {} \;
(3)$ find / -maxdepth 2 -exec echo {} \;
type
Specifying a type option allows you to filter files or directories only, example usage:
(1) list all files in this dir
(2) call shell script funtion func on every directory in the root dir.
(1)$ find . -maxdepth 1 -type f -exec echo {} \;
(2)$ find / -maxdepth 1 -type d -exec func {} \;
name & regex
The name option allows you to search for specific filenames, you can also look for files and dirs using a regex format.
Example usage: find all movies in a certain directory
$ find /path/to/dir -maxdepth 1 -regextype sed -regex ".*\.\(avi\|mp4\|mkv\)"
size
Another filter is the file size, any file or dir greater than this value will be returned. Example usage:
(1) find all empty files in current dir.
(2) find all non empty files in current dir.
(1)$ find . -maxdepth 1 -type f -size 0
(2)$ find . -maxdepth 1 -type f ! -size 0
Further examples
Move all files of this dir to a directory tmp present in .
$ find . -type f -maxdepth 1 -exec mv {} tmp \;
Convert all mkv files to mp4 files in a dir /path/to/dir and child directories
$ find /path/to/dir -maxdepth 2 -regextype sed -regex ".*\.mkv" -exec ffmpeg -i {} -o {}.mp4 \;
Convert all your jpeg files to png (don't do this, it will take very long to both find them and convert them).
$ find ~ -maxdepth 420 -regextype sed -regex '.*\.jpeg' -exec mogrify -format png {} \;
Note
The find command is a strong tool and it can prove to be fruitful to pipe the output to xargs. It's important to note that this method is superior to the following construction:
for file in $(ls)
do
some commands
done,
as the latter will handle files and directories containing spaces the wrong way.

Answer 2

In bash:
shopt -s extglob
for input in /dir/goes/here/*!(_metadata).txt
do
...
done