% uname -a FreeBSD FreeBSD 12.1-RELEASE-p8 FreeBSD 12.1-RELEASE-p8 GENERIC amd64 I have installed less from ports: % /usr/local/bin/less --version less 551 (PCRE regular expressions) Launching less with the "--mouse" option prevents selecting and copying text in xterm compliant terminals by the usual left-down-clicking. How to replicate: 1) Install less from ports 2) /usr/local/bin/less /var/log/messages. Select a block of text by left-down-clicking: this work 3) /usr/local/bin/less --mouse /var/log/messages Select a block of text by left-down-clicking: doesn't work. Workaround: selecting a block of text by [SHIFT] + left-down-clicking: works, but it is not expected behaviour. Same thing happens if $PAGER is set to "/usr/local/bin/less --mouse". My environment: % setenv USER=oc LOGNAME=oc HOME=/home/oc SHELL=/bin/tcsh BLOCKSIZE=K MAIL=/var/mail/oc PATH=/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin:/home/oc/bin TERM=xterm HOSTTYPE=FreeBSD VENDOR=amd OSTYPE=FreeBSD MACHTYPE=x86_64 SHLVL=1 PWD=/home/oc GROUP=oc HOST=FreeBSD EDITOR=vi PAGER=less LESS=-i -m +Gg Resetting $LESS to null doesn't solve the issue.
Upstream issue was reported 14th of Feb 2020. https://github.com/gwsw/less/issues/47 The workaround suggested here is to hold down shift while selecting. https://github.com/gwsw/less/issues/47#issuecomment-586270348 No comment upstream as to whether this was the intended behaviour or not, nor any pull requests to address it.
That's just how terminal emulators work. When the program running in the terminal requests to access the mouse, the terminal emulator assumes that it'll take care of text selection and copy/paste within the program. The terminal emulator's own text selection/copy/paste mechanism is then only accessible by clicking shift. There's nothing wrong with less here.