grep -l does not behave as expected on piping to xargs

Question

So I have a command like: grep "\"tool\":\"SEETEST\"" * -l Which works great standalone - it prints out a list of JSON files generated for the selected tool in the current directory.

But then, if I were to pipe it to xargs ls like that: grep "\"tool\":\"SEETEST\"" * -l | xargs ls -lSh

It prints all the files in the current directory!

How do I make it print just the matched filenames and pipe them to ls sorted by size?

can you try `grep -lZ ... | xargs -0 ...` ? that would rule out any issue due to characters like space/newline/etc in filenames — Sundeep, Jun 18 '18 at 14:36
also a suggestion: always use single quotes unless you need double quotes for interpolation.. `grep '"tool":"SEETEST"'` — Sundeep, Jun 18 '18 at 14:37
I think it only hapens if the grep command does not match anything, as seems to happen for SEETEST. Why is that? — Carmageddon, Jun 18 '18 at 15:16
Have you got a file with the name "*" in the current directory? — simon3270, Jun 18 '18 at 15:17

Miguel Ortiz · Accepted Answer · 2018-06-18T15:29:36.547

If there are not matches for xargs, then it will list all files in the current directory:

#----------- current files in the directory
mortiz@florida:~/Documents/projects/bash/test$ ls -ltr
    total 8
    -rw-r--r-- 1 mortiz mortiz 585 Jun 18 12:13 json.example2
    -rw-r--r-- 1 mortiz mortiz 574 Jun 18 12:14 json.example
#----------- using your command
mortiz@florida:~/Documents/projects/bash/test$ grep "\"title\": \"example\"" * -l
json.example
#-----------adding xargs to the previous command
mortiz@florida:~/Documents/projects/bash/test$ grep "\"title\": \"example\"" * -l | xargs ls -lSh
-rw-r--r-- 1 mortiz mortiz 574 Jun 18 12:14 json.example
#-----------adding purposely an error on "title" 
mortiz@florida:~/Documents/projects/bash/test$ grep "\"titleo\": \"example\"" * -l | xargs ls -lSh
total 8.0K
-rw-r--r-- 1 mortiz mortiz 585 Jun 18 12:13 json.example2
-rw-r--r-- 1 mortiz mortiz 574 Jun 18 12:14 json.example

If you want to use xargs and grep didn't return any match, then add "-r | --no-run-if-empty" that will prevent xargs to list all the files in the current directory:

grep "\"titleo\": \"example\"" * -l | xargs -r ls -lSh

grep -l does not behave as expected on piping to xargs

1 Answers1