Why there isn't a new line at the end of quoting a subshell and passing the results to echo?

Question

When I do ls | grep png the output of grep is:

2015-05-15-200203_1920x1080_scrot.png 2015-05-16-025536_1920x1080_scrot.png

(filename,newline,filename,newline)

then, echo $(ls | grep png) outputs:

2015-05-15-200203_1920x1080_scrot.png 2015-05-16-025536_1920x1080_scrot.png

(filename,space from word splitting,filename,newline !!from echo!!)

That is all ok, but when I do this to prevent the word splitting: echo "$(ls | grep png)", the output is:

2015-05-15-200203_1920x1080_scrot.png 2015-05-16-025536_1920x1080_scrot.png

And my question is, where is the second newline (one should be from grep and one from echo)?

cuonglm · Accepted Answer · 2015-05-17 16:22:21Z

That's newline from echo, you can verify by using echo -n to suppress trailing newline:

echo -n "$(ls | grep png)"

Command substitution remove all trailing newlines, last newline was added by echo, grep has nothing to do here.

"Command substitution remove all trailing newlines" - thats it! Thank you — MichalH
– MichalH, Commented May 17, 2015 at 16:34

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