xargs and line-by-line pipe

Question

I have 3 files: a.txt, b.txt and c.txt. I want to create 3 files: a.test, b.test and c.test containing the simple text abracadabra.

Basicaly, the point is to create the .test files for each .txt file, and fill them with some text. I am trying to use xargs to do this.

anlx2626> ls
a.txt  b.txt  c.txt

anlx2626> ls *.txt | awk -F'.txt' '{print $1}' | xargs -I {} echo "abracadabra" > {}.test

anlx2626> ls *.test
ls: No match.

Could someone point out why using the {} placeholder for line-by-line pipe doesn't work the way I expect it to?

Answer 1

In this code:

xargs -I {} echo "abracadabra" > {}.test

xargs will not see the redirection operator > at all: it will be interpreted by your shell instead, creating a file named, literally, {}.test.

One way to do what you ask using xargs is this, which lets sh interpret the redirection operator:

xargs sh -c 'for i do echo abracadrabra > "$i"; done' sh

But you would probably be better off not using xargs at all, which other answers explain how to do.

Answer 2

awk can output text, not need for echo or xargs. Your approach has issues for file names with more than one dot, like foo-1.2.txt.

It would also have issues for filenames with newlines in them or if there are directories whose name ends in .txt.

For once, I'd use a loop here, for instance with zsh:

(set -o noclobber; for f (*.txt(N)) echo abracadabra > $f:r.test)

Or POSIXly:

(set -o noclobber
 for f in *.txt; do
   echo abracadabra > "${f%.*}.test"
 done)

The noclobber is to avoid overriding an already existing file. Note that it omits hidden files. If there's no txt file, the POSIX sh variant will create a *.test file.

Answer 3

Although this has been answered adequately, I'm just adding this to show another way:

while IFS= read -r
do
echo abracadabra > "${REPLY}.test"
done < <(find . -maxdepth 1 -name "*.txt" -exec basename -s .txt {} \;)

Here find is used to list the text files. maxdepth is used to stop find from recursing into child folders. basename -s .txt is being used to remove the txt extension right at the start because except to list the names we don't need it at all. In the while loop, we simply use the name without the extension, and use string substitution to add the .test extension, while echoing to the file. Note that we have used the default variable of while, which is $REPLY.

Answer 4

for l in $(ls *.txt); do echo "abrakadabra" > $l; done