How to display trailing whitespaces in the text file?

Question

I'd like to be able to print and see the trailing whitespaces in the text file (just display, not remove).

I've tried with cat -v which suppose to display non-printing characters, but it doesn't display them as expected (no visual difference between the lines). E.g.

$ printf "foo\nbar \t\n" > file.txt
$ cat -v file.txt 
foo
bar     

By print/display whitespaces I mean some visual human indication that the trailing whitespace is there in comparison to other lines without, either by some special character, color (like when files are displayed using git diff) or something similar.

Is there any other way?

---

Note: I'm on macOS Sierra, however I've got access to both GNU and BSD cat commands:

$ type -a cat
cat is /usr/local/opt/coreutils/libexec/gnubin/cat
cat is /bin/cat
$ cat --version
cat (GNU coreutils) 8.28
$ /bin/cat --version
/bin/cat: illegal option -- -
usage: cat [-benstuv] [file ...]

Solution

gnu cat has the -E switch for that so with an input like

printf " one \ntwo \t\n"

it will print

 one $
two    $

There are many ways to emulate that behaviour e.g. use sed in "raw" mode:

sed -n l infile

or

paste -d '$' infile /dev/null

or use any text processing tool to add a $ before each newline...

You might also try something like

less -p '[[:blank:]]+$' infile

which will highlight the pattern (in this case the trailing blanks)...

Comments

[kenorb]

Thanks, seems to work fine, at least better than -v. -E doesn't exist for /bin/cat, but I've got GNU cat installed as well.

[Stephen Kitt]

cat -v does work, it just doesn’t do what you think it does — try cat -v /dev/urandom | head to see how it affects output.

[Sanket]

@kenorb -E does exist for /bin/cat , which version are you talking about

[kenorb]

cat -v prints non-printing characters fine, however whitespace is still a whitespace, so it's not really human visible in the terminal.

[kenorb]

@Sanket $ /bin/cat -E file.txt -> /bin/cat: illegal option -- E.

[Sanket]

# /bin/cat -E firstOne.txt It outputs the content "kkjkl" my case