Bash: dirname not working with xargs

Question

The following command:

echo ./test/test2/test23 | xargs -I "{}" echo `dirname "{}"`  

Outputs: . (not as expected)

The following command:

echo ./test/test2/test23 | xargs -I "{}" echo `dirname ./test/test2/test23` 

Outputs: ./test/test2 (as expected)

The following command:

echo ./test/test2/test23 | xargs -I "{}" echo `echo "{}"`  

Outputs: ./test/test2/test23 (as expected)

Why is the first command not outputting ./test/test2?

Answer 1

The reason for the unexpected output is that the subshell substitution of dirname "{}" is being executed first (having an output of .), making the command effectively echo "./test/test2/test23" | xargs -I "{}" echo .. Since there is no match for xargs' specified marker of {}, there is nothing replaced, and echo . runs as expected, with output of ..