[SOLVED] Loop trough list of files, two at the time

Boel · 10-27-2011, 08:16 AM

Hey,

I have a directory of files, named:
File_1_1, File_1_2, File_2_1, File_2_2, etc..

I want to loop trough the files in this directory pairwise

Code:

for file1 & file2 in /path/to/dir/*
do
 execute command on $file1 and $file2
done

How can I accomplish this? It is important that File_1_1 i paired with File_1_2.

Thanks a lot!

grail · 10-27-2011, 08:23 AM

Maybe try a while loop and perform second read inside the loop

allend · 10-27-2011, 08:38 AM

This seems to work if run in the directory containing the files.

Code:

#! /bin/bash

for fn in *_1
do
  if [ -f "${fn%%_1}"_2 ]; then
    echo $fn, ${fn%%_1}_2
  fi
done

David the H. · 10-27-2011, 02:13 PM

As long as the number of files is not unreasonably large, you could load them into an array, then can call them by address number.

Code:

array=( * )

for (( i=0; i<=${#array[@]}; i+=2 )) ; do

	echo "${array[i]} ${array[i+1]}"

done

It assumes that the files sort out properly when globbed though. Try running "echo *" first to see what order the shell puts them in.

Even better would be to use two arrays, loaded by globs that match the paired filenames.

Code:

array1=( File_*_1 )
array2=( File_*_2 )

for i in "${!array1[@]}"; do

	echo "${array1[i]} ${array2[i]}"

done

Assuming the files are all named in the format you posted, they should match up. Do note that filenames with numbers in them sort as ascii strings, rather than integers, so File_10_1 would come before File_1_1. But at least the pairings will come out the same.