What is "-bash: !": event not found"

Solution 1:

You can turn off history substitution using set +H.

Solution 2:

! is a special character to bash, it is used to refer to previous commands; eg,

!rm

will recall and execute the last command that began with the string "rm", and

!rm:p

will recall but not execute the last command that began with the string "rm". bash is interpreting the exclamation mark in echo "reboot your instance!" as "substitute here the last command that began with the character(s) immediately following the exclamation mark", and grumbles at you that it cannot find an event (command) in your history that began with a single double-quote.

Try

echo reboot your instance\!

to protect (escape) the exclamation mark from bash.

Solution 3:

To solve your original problem, try using single quotes, rather than double quotes. With the latter, bash will attempt to expand certain characters before passing the result on to the command (echo in this case). With single quotes, bash passes the entire string, unchanged.

! is used in commands to refer to the command line history. See: http://tldp.org/LDP/abs/html/abs-guide.html#HISTCOMMANDS for a full set. With the above example, bash is trying to expand !" as a reference to an event before echo gets a look in, hence the error.

Note that in scripts, all of the history commands are disabled, as they only make sense in an interactive shell.

The only one I use on a regular basis, is !$. It expands to the last argument of the previous command. It's a useful shorthand in places.

Solution 4:

Just put a space between ! and " than it'll work.

Solution 5:

Yes, ! is a special character to bash, it is used to refer to previous commands.

Few of the ways you can handle the situation

The following will output the string as it is

echo 'Reboot your instance!'

The following will execute the command and concatenate the string

echo 'escaping #'" adding `which python` to the string"
echo '#!'`which python`