Concatenating Files And Insert New Line In Between Files

I have multiple files which I want to concat with cat. Let's say

File1.txt 
foo

File2.txt
bar

File3.txt
qux

I want to concat so that the final file looks like:

foo

bar

qux

Instead of this with usual cat File*.txt > finalfile.txt

foo
bar 
qux

What's the right way to do it?

You can do:

for f in *.txt; do (cat "${f}"; echo) >> finalfile.txt; done

Make sure the file finalfile.txt does not exist before you run the above command.

If you are allowed to use awk you can do:

awk 'FNR==1{print ""}1' *.txt > finalfile.txt

If you have few enough files that you can list each one, then you can use process substitution in Bash, inserting a newline between each pair of files:

cat File1.txt <(echo) File2.txt <(echo) File3.txt > finalfile.txt

If it were me doing it I'd use sed:

sed -e '$s/$/\n/' -s *.txt > finalfile.txt

In this sed pattern $ has two meanings, firstly it matches the last line number only (as a range of lines to apply a pattern on) and secondly it matches the end of the line in the substitution pattern.

If your version of sed doesn't have -s (process input files separately) you can do it all as a loop though:

for f in *.txt ; do sed -e '$s/$/\n/' $f ; done > finalfile.txt

This works in Bash:

for f in *.txt; do cat $f; echo; done

In contrast to answers with >> (append), the output of this command can be piped into other programs.

Examples:

• for f in File*.txt; do cat $f; echo; done > finalfile.txt
• (for ... done) > finalfile.txt (parens are optional)
• for ... done | less (piping into less)
• for ... done | head -n -1 (this strips off the trailing blank line)

You may do it using xargs if you like, but the main idea is still the same:

find *.txt | xargs -I{} sh -c "cat {}; echo ''" > finalfile.txt

That's how I just did it on OsX 10.10.3

for f in *.txt; do (cat $f; echo '') >> fullData.txt; done

since the simple 'echo' command with no params ended up in no new lines inserted.

In python, this concatenates with blank lines between files (the , suppresses adding an extra trailing blank line):

print '\n'.join(open(f).read() for f in filenames),

Here is the ugly python one-liner that can be called from the shell and prints the output to a file:

python -c "from sys import argv; print '\n'.join(open(f).read() for f in argv[1:])," File*.txt > finalfile.txt