Bash - (Return|Exit) (Value|Status)

The return status (also known as Exit Status of Exit Code) of a simple command is its exit status as provided by:

• the posix 1003.1 waitpid function,
• or 128+n if the command was terminated by signal n.

? is a special parameter that expands to the status of the most recently executed foreground pipeline.

echo $?

0

/usr/bin/somecommand || /bin/true

RESULT=$?
if [ ${RESULT} -ne 0 ];
then
    echo -e "\nLast command has failed."
else
    echo -e "\nLast command has succeeded."
fi 

[ "$?" -eq 0 ] && echo success  || echo failure