Show special characters in Unix while using 'l

Question

I would like to know how to view special characters while using 'less' command. For instance I want to see the non-printable characters with a special notation. For instance in 'vi' editor I use "set list on" to see the line termination characters represented by dollar '$' character. Similarly I would want to do this using 'less' command.

I referred Unix less manual, but to no avail.

Answer 1

For less use -u to display carriage returns (^M) and backspaces (^H), or -U to show the previous and tabs (^I) for example:

$ awk 'BEGIN{print "foo\bbar\tbaz\r\n"}' | less -U 
foo^Hbar^Ibaz^M

(END)

Without the -U switch the output would be:

fobar   baz

(END)

See man less for more exact description on the features.

Answer 2

In the same spirit as https://stackoverflow.com/a/6943976/7154924:

cat -A

-A, --show-all
       equivalent to -vET
-v, --show-nonprinting
       use ^ and M- notation, except for LFD and TAB
-E, --show-ends
       display $ at end of each line
-T, --show-tabs
       display TAB characters as ^I

Alternatively, or at the same time, you can pipe to tr to substitute arbitrary characters to the desired ones for display, before piping to a pager like less if desired.

Answer 3

All special, nonprintable characters are displayed using ^ notation in less. However, line feed is actually printable (just make a new line), so not considered special, so you'll have problems replacing it. If you just want to see line endings, the easiest way might be

sed -e 's/$/$/' | less

Answer 4

less will look in its environment to see if there is a variable named LESS

You can set LESS in one of your ~/.profile (.bash_rc, etc, etc) and then anytime you run less from the comand line, it will find the LESS.

Try adding this

 export LESS="-CQaix4"

This is the setup I use, there are some behaviors embedded in that may confuse you, so ...

You can find out about what all of these mean from the help function in less, just tap the 'h' key and nose around, or run less --help.

edit

I looked at the help, and noticed there is also an -r option

-r  -R  ....  --raw-control-chars  --RAW-CONTROL-CHARS
                Output "raw" control characters.

I agree that cat may be the most exact match to your stated needs.

 cat -vet file | less

Will add '$' at end of each line and convert tab char to visual '^I'.

 cat --help
   (edited)
    -e                       equivalent to -vE
    -E, --show-ends          display $ at end of each line
    -t                       equivalent to -vT
    -T, --show-tabs          display TAB characters as ^I
    -v, --show-nonprinting   use ^ and M- notation, except for LFD and TAB

I hope this helps.

Answer 5

You can do that with cat and that pipe the output to less:

cat -e yourFile | less

This excerpt from man cat explains what -e means:

   -e     equivalent to -vE

   -E, --show-ends
          display $ at end of each line

   -v, --show-nonprinting
          use ^ and M- notation, except for LFD and TAB