I have the file dir1.txt that contains the names of the following directories:


Directory 2 contains files 2_1.txt and 2_2.txt
Directory 3 contains files 3_1.txt and 3_2.txt
Directory 4 contains files 4_1.txt and 4_2.txt
Each file contains two lines.

Then I have created the following nested loop:

while IFS=read -r line
  for j in "$line/*"
  do sed -e '$s/$/\n/' $j
    #cat $j; echo
  done >> output.txt
done < "$input"

Basically, I want to have a blank line between the concatenated files. With the above loop, I am only getting a blank line between the last file content in dir 2 and the first file in dir 3, as well as last file content in dir 3 and first file in dir 4 but I also want a blank line between the concatenated content of the files in the same directory. I have tried with cat $j; echo (commented out above) but to no avail. Tried with a nested for loop, again - I am getting the same outcome. I think my logic is wrong.


Your logic is correct, but I had to make a few modifications to get it working.

  1. Added a missing space after IFS (otherwise error)
  2. Changed the quoted "$line/*" to "$line"/* (otherwise sed: can't read 2/*: No such file or directory)
  3. Quoted $j (only for better style)

Both the sed and the cat/echo version do what they should.


while IFS= read -r line
        for j in "$line"/*
                sed -e '$s/$/\n/' "$j"
                #cat "$j"; echo
        done >> output.txt
done < "$input"
  • Thank you, Freddy. Your corrections made a difference and the code worked beautifully. Sorry, I cannot upvote you as I have fewer than 15 reps. – soti84 May 15 at 18:46

When in doubt, use comments and stderr output.

Also some aspects of your script didn't work for me on GNU bash, version 4.2.46(2)-release (x86_64-redhat-linux-gnu)


# Cycle through input
for dir in $(cat $input) 
    # Prints to stderr
    (echo "INFO - Dir: $dir" 1>&2)

    # Is dir a directory?
    if [ -d $dir ]
        # Cycle through files
        for file in $dir/*   
            # Prints to stderr
            (echo "INFO - File: $file" 1>&2)

            # Print contents
            cat $file

            # Blank line.
done >> output.txt 
  • Thank you very much for your suggestion, SHawarden. It, too, worked like a charm. Your adviceon the use of comments and stderr are highly appreciated. To a person like me who is still learning,this is indespensable. I wish I could also mark your reply as the chosen correct solution. Apologies but I have fewer than 15 reps so I cannot upvote your reply. – soti84 May 15 at 18:55

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