Ubuntu – Change less (pager) default options

lesspagerUbuntu

I'm using Ubuntu 10.04. My default pager(set using update-alternatives, not $PAGER) is less. The problem is, when I use ri(Ruby documentation tool) with the '-f ansi' mode, less shows the escape sequences(such as 'ESC[36m') instead of displaying the text in color. I can force it to show colors by manually piping the output to less with the -R option, for example:

ri -f ansi String | less -R

However, I'd like this to be the default option when less is used as a pager.

Note: I'm aware that more and most show colors by default, but I use less because of the vi-like key bindings.

Best Answer

I found the answer somewhere else. I needed to use lesskey to set up less's options:

$ lesskey -
#env
LESS = -R

Then Ctrl+d

did the trick. I'm still not sure why less ignores $LESS though.

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Linux – Use `less` pager on file with non-standard encoding

Hm, apparently less cannot do this. The part in less' sourcecode that implements the "following" seems to be:

A_F_FOREVER:
                        /*
                         * Forward forever, ignoring EOF.
                         */
                        if (ch_getflags() & CH_HELPFILE)
                                break;
                        cmd_exec();
                        jump_forw();
                        ignore_eoi = 1;
                        while (!sigs)
                        {
                                make_display();
                                forward(1, 0, 0);
                        }
                        ignore_eoi = 0;

As far as my (limited) knowledge of C goes, this means that if "follow" is activated, less will:

seek to the end of input
read and update the display in a loop, until Ctrl-C is pressed

If input is a pipel, 1. will not return until the pipe signals EOF. If I use tail -f xx|less, the pipe will never signal EOF, so less hangs :-(.

I did however find a way to get what I want:

 tail -f inputfile | recode latin1.. > /tmp/tmpfile

then

less +F /tmp/tmpfile

This will work, because it lets less +F work on a real file. It's still somewhat awkward, because recode apparently only processes data in blocks of 4096 bytes, but it works...

N automatically scrolling, time-delayed Unix pager command

A simple solution using bash:

function scroll
{
    while read -r ; do echo "$REPLY" ; sleep ${1:-0.5} ; done
}

Usage

long_command | scroll [delay]

delay is optional and defaults to 0.5.

Exit with Ctrl+C

Best Answer

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Linux – Use `less` pager on file with non-standard encoding

N automatically scrolling, time-delayed Unix pager command

Usage

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