grep after grep : No such file or directory

Question

To create a test file contains blanks in the filename first:

vim  "/tmp/it is a test.txt"
bash  escape

Search with grep:

grep    -lr   'bash'  /tmp
/tmp/it is a test.txt

I want to grep command after the grep:

grep    -lr   'bash'  /tmp  | xargs grep  escape
grep: /tmp/it: No such file or directory
grep: is: No such file or directory
grep: a: No such file or directory
grep: test.txt: No such file or directory

So i add -0 in xargs:

grep    -lr   'bash'  /tmp | xargs -0 grep  escape
grep: /tmp/it is a test.txt
: No such file or directory

I find the reason:

grep    -lr   'bash'  /tmp | xargs -0 
grep: /tmp/it is a test.txt
#a blank line at the bottom

xargs -0 add a blank line!
How can suppress the output : No such file or directory ?

Answer 1

As you may have guessed, the first version you tried

grep -lr 'bash' /tmp | xargs grep escape

failed because xargs assumes arguments taken from standard input are delimited by:

space, tab, newline and end-of-file.

You were on the good track by adding the -0 CLI option:

grep -lr 'bash' /tmp | xargs -0 grep escape

But to make it fully working, you'll also need to ensure that xargs's input is indeed delimited by NUL characters.

Hence the following command that relies on tr:

grep -lr 'bash' /tmp | tr '\n' '\0' | xargs -0 grep escape

Alternatively, a better solution amounts to directly using grep's --null CLI option:

grep -lr --null 'bash' /tmp | xargs -0 grep escape

or more concisely:

grep -lrZ 'bash' /tmp | xargs -0 grep escape

As an aside

I find the reason:
xargs -0 add a blank line!

To explain this further:

xargs -0 alone amounts to xargs -0 echo, and because of -0, xargs sees the final newline printed by grep (included as you didn't use the --null CLI option) as a character that is part of the filename… which is then printed by echo.

Answer 2

grep has the option -s or --no-messages to suppress error messages about nonexistent or unreadable files.