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 '$' character. Similarly I would want to do this using 'less' command.
I referred Unix less manual, but to no avail.
less will look in its environment to see if there is a variable named LESS
You can set LESS in one of your ~/.profile (.bash_rc, etc, etc) and then anytime you run less from the comand line, it will find the LESS.
Try adding this
export LESS="-CQaix4"
This is the setup I use, there are some behaviors embedded in that may confuse you, so you can find out about what all of these mean from the help function in less, just tap the 'h' key and nose around, or run less --help.
Edit:
I looked at the help, and noticed there is also an -r option
-r -R .... --raw-control-chars --RAW-CONTROL-CHARS
Output "raw" control characters.
I agree that cat may be the most exact match to your stated needs.
cat -vet file | less
Will add '$' 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.
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
Now, sometimes you already have less open, and you can't use cat on it. For example, you did a | less, and you can't just reopen a file, as that's actually a stream.
If all you need is to identify end of line, one easy way is to search for the last character on the line: /.$. The search will highlight the last character, even if it is a blank, making it easy to identify it.
That will only help with the end of line case. If you need other special characters, you can use the cat -vet solution above with marks and pipe:
mamb'acat -vet and view the result in another less command: |bcat -vet | lessThis will open another less process, which shows the result of running cat -vet on the text that lies between marks a and b.
If you want the whole thing, instead, do g|$cat -vet | less, to go to the first line and filter all lines through cat.
The advantage of this method over less options is that it does not mess with the output you see on the screen.
One would think that eight years after this question was originally posted, less would have that feature... But I can't even see a feature request for it on https://github.com/gwsw/less/issues
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.
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
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.
Source: Stackoverflow.com