The
err() and
warn() family of functions display a formatted error message on the standard error output. In all cases, the last component of the program name, a colon character, and a space are output. If the
fmt argument is not
NULL, the formatted error message is output. In the case of the
err(),
verr(),
warn(), and
vwarn() functions, the error message string affiliated with the current value of the global variable
errno is output next, preceded by a colon character and a space if
fmt is not
NULL. In all cases, the output is followed by a newline character. The
errx(),
verrx(),
warnx(), and
vwarnx() functions will not output this error message string.
The
err(),
verr(),
errx(), and
verrx() functions do not return, but instead cause the program to terminate with the status value given by the argument
status. It is often appropriate to use the value
EXIT_FAILURE, defined in
<stdlib.h>, as the
status argument given to these functions.