1

Ok, I have many files in a folder that have the string "$varname.txt"` in their name:

for file in find output/ -name "*$varname*.txt" -type f; do echo $file; done

...

now these files all have two lines and 9 columns to them. I want to add the content of line 2, col 9 to the end of their filname (right before the .txt).

So I know how to print the value of in cell(2, 9) of all these files:

find output/ -name "*$varname*.txt" -type f -exec awk -F' ' 'NR==2{print $9}' {} \;

What I struggle with is how to put that string as the last thing before the extension in those filenames

3

You need to capture the value and construct the new filename with it.

find output/ -name "*$varname*.txt" -type f -exec sh -c '
    for file; do
        value=$(awk "NR==2 {print \$9; exit}" "$file")
        echo mv "$file" "${file%.*}$value.${file##*.}"
    done
' sh {} +

I'm calling a shell script in the -exec directive, passing several filenames to it (with -exec ... + instead of -exec ... \;)

The trailing "sh" becomes $0, and the filenames go into $1, $2, etc

  • I came to the exact same solution, but I’d replace txt with ${file##*.}. – dessert Jun 24 '18 at 10:56
  • 1
    Why? We are explicitly looking for txt files based on the find command. We already know exactly what the filename extension is. – glenn jackman Jun 24 '18 at 10:58
  • 1
    Then again, if we change the -name pattern, we wouldn't have to also change the sh code. Or if the name pattern is dynamic. I see your point – glenn jackman Jun 24 '18 at 11:07
  • Exactly – it’s a good thing to make code as universally applicable as possible. Someone searching for “add value to file name” might stumble across this and wonder. – dessert Jun 24 '18 at 11:09
  • 1
    @user2413 glenn forgot to mention that this only prints what will be done, you need to remove echo to perform the renaming, see my answer below where I do the same. – dessert Jun 24 '18 at 11:28
2

Here’s a GNU parallel Install parallel approach:

find output/ -name "*$varname*.txt" -type f -print0 |
parallel -0 'echo mv {} {.}$(awk -F" " "NR==2{print\$9}" {}).{=s/.*\.//=}'

This pipes the zero-delimited file list to parallel which lists the renaming commands – remove echo if it does the right thing. parallel comes with handy replacement strings, {} is replaced by the (currently processed) input file name, {.} by the input filename without extension and with {=perl expression=} you can run anything perl can do, like a substitution here. The output of your awk command is simply added using Command Substitution.

  • 1
    Thanks for the idea. In this case, this is part of a bash function that will itself be called by parallel (so in my individual use case it is a bit moot hence my awarding the points to @glenn jackman's answer) but I'm sure other reader will appreciate doing these sort of tasks 8 times faster! – user2413 Jun 24 '18 at 11:30

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