As I have mentioned here for some reason whenever I try to use CTRL key for any of the keyboard shortcuts, it prints the caret sign ^. Here is my .bashrc file:

# ~/.bashrc: executed by bash(1) for non-login shells.
# see /usr/share/doc/bash/examples/startup-files (in the package bash-doc)
# for examples

# If not running interactively, don't do anything
case $- in
    *i*) ;;
      *) return;;

# don't put duplicate lines or lines starting with space in the history.
# See bash(1) for more options

# append to the history file, don't overwrite it
shopt -s histappend

# for setting history length see HISTSIZE and HISTFILESIZE in bash(1)

# check the window size after each command and, if necessary,
# update the values of LINES and COLUMNS.
shopt -s checkwinsize

# If set, the pattern "**" used in a pathname expansion context will
# match all files and zero or more directories and subdirectories.
#shopt -s globstar

# make less more friendly for non-text input files, see lesspipe(1)
[ -x /usr/bin/lesspipe ] && eval "$(SHELL=/bin/sh lesspipe)"

# set variable identifying the chroot you work in (used in the prompt below)
if [ -z "${debian_chroot:-}" ] && [ -r /etc/debian_chroot ]; then
    debian_chroot=$(cat /etc/debian_chroot)

# set a fancy prompt (non-color, unless we know we "want" color)
case "$TERM" in
    xterm-color|*-256color) color_prompt=yes;;

# uncomment for a colored prompt, if the terminal has the capability; turned
# off by default to not distract the user: the focus in a terminal window
# should be on the output of commands, not on the prompt

if [ -n "$force_color_prompt" ]; then
    if [ -x /usr/bin/tput ] && tput setaf 1 >&/dev/null; then
    # We have color support; assume it's compliant with Ecma-48
    # (ISO/IEC-6429). (Lack of such support is extremely rare, and such
    # a case would tend to support setf rather than setaf.)

if [ "$color_prompt" = yes ]; then
    PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '
    PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$ '
unset color_prompt force_color_prompt

# If this is an xterm set the title to user@host:dir
case "$TERM" in
    PS1="\[\e]0;${debian_chroot:+($debian_chroot)}\u@\h: \w\a\]$PS1"

# enable color support of ls and also add handy aliases
if [ -x /usr/bin/dircolors ]; then
    test -r ~/.dircolors && eval "$(dircolors -b ~/.dircolors)" || eval "$(dircolors -b)"
    alias ls='ls --color=auto'
    #alias dir='dir --color=auto'
    #alias vdir='vdir --color=auto'

    alias grep='grep --color=auto'
    alias fgrep='fgrep --color=auto'
    alias egrep='egrep --color=auto'

# colored GCC warnings and errors
#export GCC_COLORS='error=01;31:warning=01;35:note=01;36:caret=01;32:locus=01:quote=01'

# some more ls aliases
alias ll='ls -alF'
alias la='ls -A'
alias l='ls -CF'

# Add an "alert" alias for long running commands.  Use like so:
#   sleep 10; alert
alias alert='notify-send --urgency=low -i "$([ $? = 0 ] && echo terminal || echo error)" "$(history|tail -n1|sed -e '\''s/^\s*[0-9]\+\s*//;s/[;&|]\s*alert$//'\'')"'

# Alias definitions.
# You may want to put all your additions into a separate file like
# ~/.bash_aliases, instead of adding them here directly.
# See /usr/share/doc/bash-doc/examples in the bash-doc package.

if [ -f ~/.bash_aliases ]; then
    . ~/.bash_aliases

# enable programmable completion features (you don't need to enable
# this, if it's already enabled in /etc/bash.bashrc and /etc/profile
# sources /etc/bash.bashrc).
if ! shopt -oq posix; then
  if [ -f /usr/share/bash-completion/bash_completion ]; then
    . /usr/share/bash-completion/bash_completion
  elif [ -f /etc/bash_completion ]; then
    . /etc/bash_completion

# export TERM=”screen-256color” 

if [ -f `which powerline-daemon` ]; then
  powerline-daemon -q
  . /usr/local/lib/python3.6/dist-packages/powerline/bindings/bash/powerline.sh

And when I run stty -a I get:

speed 9600 baud; rows 55; columns 204; line = 0; intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = M-^?; eol2 = M-^?; swtch = ; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W; lnext = ^V; discard = ^O; min = 1; time = 0; -parenb -parodd -cmspar cs8 -hupcl -cstopb cread -clocal -crtscts -ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl ixon -ixoff -iuclc ixany imaxbel iutf8 opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0 isig icanon iexten echo echoe -echok -echonl -noflsh -xcase -tostop -echoprt echoctl echoke -flusho -extproc

I need to diagnose why this has happened and how I can resolve it.

closed as off-topic by jasonwryan, l0b0, G-Man, JigglyNaga, Isaac Dec 10 '18 at 12:57

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "This question has been posted on multiple sites. Cross-posting is strongly discouraged; see the help center and community FAQ for more information." – jasonwryan, G-Man, JigglyNaga

  • 2
    Make a copy of your .bashrc and eliminate lines until it works as expected. Which line is responsible for this change in the behaviour? – l0b0 Dec 9 '18 at 21:57
  • ok, that would be a bit cumbersome. I was hoping I could receive a more straightforward approach. – Foad Dec 9 '18 at 21:58
  • 1
    You failed to say that this problem appear when you ssh from a Mac to a Ubuntu system. Have you tried a reboot (of both computers) already ? – Isaac Dec 10 '18 at 12:56
  • 1
    @Foad For Both computers?. That seems odd. That a ctrl-c prints a ^C is not so odd, it is a very old way to encode control characters by shifting the seventh bit. So ctrl-a (001) is ^A, ctrl-b (002) is ^B, etc. Is a ctrl-c still working? To test: execute sleep 20 and press Ctrl-C to find out if it stops. If it does, the chracters are working, if not, the console is not receiving the characters (I suspect it is). – Isaac Dec 11 '18 at 10:12
  • 1
    Then, if the console receives the characters, what do you see if you execute cat -A and type some control characters like Ctrl-A, Ctl-b, Alt-tab, the arrows, etc. If the X server is correctly capturing the shortcuts, the Alt-tab should not be received by your console application, if it is, there is a problem with X shortcuts. Please test and report back. @Foad – Isaac Dec 11 '18 at 10:12

I would look at the following:

xmodmap -pke

Like on my system the control keys are:

  • This will list the current mapping of your keys. If you find the offending setting you can reassign that key.

    keycode  37 = Control_L NoSymbol Control_L
    keycode 105 = Control_R NoSymbol Control_R

Use xev to find out what the keystream is, then remap it back to control.

  • My xev shows this for control:

    KeyRelease event, serial 37, synthetic NO, window 0x3000001,
    root 0x15c, subw 0x0, time 5417642, (167,-18), root:(195,67),
    state 0x14, keycode 37 (keysym 0xffe3, Control_L), same_screen YES,
    XLookupString gives 0 bytes: 
    XFilterEvent returns: False

Something like:

xmodmap -e "keycode 37 = Control_R NoSymbol Control_R"

Would make my control key function normally.

To make this permanent edit your xorg configuration file to reflect the new mapping.

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