function prints the given runtime error message to stderr and terminates
execution of the script with a return value of 1.
The message can be provided as one or more arguments as depicted by
all arguments are concatenated together into a single line.
The printed message has the following form, where
is determined by
progname: E: message1 .. messageN
should be used to bail out on erroneous conditions not directly caused by an
invalid invocation of the script.
For errors caused directly by the user, such as specifying an incorrect flag to
the program, should be reported using