I'm looking to create files with names based on the command output of the previous command i.e. if i run
find . -name *.mp4 | wc -l > filename
So that the output of the amount of files of that type is the filename of the created file.
1 Answer
Here's a solution that renames the file after it has been created:
find . -name *.mp4 | wc -l > filename && mv filename `tail -n 1 filename`
What is happening in this one-liner:
find . -name *mp4 | wc -l > filename : Finds files with mp4 suffix and then counts how many were found and redirects the output to a file named filename
tail -n 1 filename: Outputs the very last line in the file named filename. If you put backticks around it (`tail -n 1 filename`) then that statement is executed and replaced by the text it returns.
mv filename `tail -n 1 filename`: Renames the original file named filename to the executed statement above.
When you combine these with &&, the second statement only runs if the first was successful.
4 Comments
John13
Awesome that worked, now i'm trying to understand why it works :)
John13
Figured it out! the and operand just adds another command to run instead of the output and move is used to rename the file from its contents using the evaluation of the tail command's output of the file contents, very clever actually and i really learned a lot of shell here, although i found many people saying $() should be used instead of backticks for eval
John13
Thanks for the answer and clarification @alexbclay
Aaron D. Marasco
If you already have a file named
filename, it's in trouble. That's why I mentioned mktemp.
mktempand then rename once you've parsed the output.n=$(ls -1 *.mp4 | wc -l); touch "$n-mp4"? (or...; echo "$n" > "$n-mp4")lswill not work. (not without adjustingglobstarin bash, etc..) andfindis the proper tool. Which you can change ton=$(find . -type f -name *.mp4 | wc -l); echo "$n" > "$n-mp4"; unset n