err(), verr(), errx(), verrx(), warn(), vwarn(), warnx(), vwarnx() - formatted error messages
#include <err.h>
void err (int eval, const char *fmt, ...)
void verr (int eval, const char *fmt, va_list args)
void errx (int eval, const char *fmt, ...)
void verrx (int eval, const char *fmt, va_list args)
void warn (const char *fmt, ...)
void vwarn (const char *fmt, va_list args)
void warnx (const char *fmt, ...)
void vwarnx (const char *fmt, va_list args)
The err(3) and warn(3) 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 first. If the fmt argument is not NULL, the formatted error message, a colon character, and a space are output. In the case of the err(3), verr(3), warn(3), and vwarn(3) functions, the error message string affiliated with the current value of the global variable errno is output. In all cases, the output is followed by a newline character.
The err(3), verr(3), errx(3), and verrx(3) functions do not return, but exit with the value of the argument eval.
Display the current errno information string and exit:
if ((p = malloc(size)) == NULL)
err(1, NULL);
if ((fd = open(file_name, O_RDONLY, 0)) == -1)
err(1, "%s", file_name);
Display an error message and exit:
if (tm.tm_hour < START_TIME)
errx(1, "too early, wait until %s", start_time_string);
Warn of an error:
if ((fd = open(raw_device, O_RDONLY, 0)) == -1)
warnx("%s: %s: trying the block device",
raw_device, strerror(errno));
if ((fd = open(block_device, O_RDONLY, 0)) == -1)
err(1, "%s", block_device);
strerror(3)