ERR(3)

NAME
err, verr, errx, verrx, warn, vwarn, warnx, vwarnx, err_set_file, err_set_exit - formatted error messages

SYNOPSIS
#include <err.h>
void
err(int eval, const char *fmt, ...);
void
errx(int eval, const char *fmt, ...);
void
warn(const char *fmt, ...);
void
warnx(const char *fmt, ...);
void
err_set_file(void *fp);
void
err_set_exit(void (*exitf)(int));
#include <stdarg.h>
void
verr(int eval, const char *fmt, va_list args);
void
verrx(int eval, const char *fmt, va_list args);
void
vwarn(const char *fmt, va_list args);
void
vwarnx(const char *fmt, va_list args);

DESCRIPTION
The err() and warn() family of functions display a formatted error message on the standard error output, or on another file specified using the err_set_file() function. 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, a colon character, and a space are 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. In all cases, the output is followed by a newline character.

The err(), verr(), errx(), and verrx() functions do not return, but exit with the value of the argument eval. The err_set_exit() function can be used to specify a function which is called before exit(3) to perform any necessary cleanup; passing a null function pointer for exitf resets the hook to do nothing.

EXAMPLES
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);

SEE ALSO
exit(3), strerror(3)

HISTORY
The err() and warn() functions first appeared in 4.4BSD.