err man page on SmartOS

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ERR(3C)								       ERR(3C)

       err,  verr,  errx,  verrx, warn, vwarn, warnx, vwarnx - formatted error

       #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() and warn() family of functions display a formatted error mes‐
       sage  on the standard error output. In all cases, the last component of
       the program name, followed by a colon character and a space,  are  out‐
       put.  If	 the  fmt argument is not NULL, the formatted error message is
       output. In the case of the err(), verr(),  warn(),  and	vwarn()	 func‐
       tions,  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()	 func‐
       tions 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.

       Example	1  Display  the current errno information string and terminate
       with status indicating failure.

	 if ((p = malloc(size)) == NULL)
	     err(EXIT_FAILURE, NULL);
	 if ((fd = open(file_name, O_RDONLY, 0)) == -1)
	     err(EXIT_FAILURE, "%s", file_name);

       Example 2 Display an error message and terminate with status indicating

	 if (tm.tm_hour < START_TIME)
	     errx(EXIT_FAILURE, "too early, wait until %s", start_time_string);

       Example 3 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)
	     warn("%s", block_device);

       It  is  important  never	 to pass a string with user-supplied data as a
       format without using `%s'. An attacker can put format specifiers in the
       string  to  mangle the stack, leading to a possible security hole. This
       holds true even if the string has been built ``by hand'' using a	 func‐
       tion like snprintf(3C), as the resulting string can still contain user-
       supplied conversion specifiers for later interpolation by the err() and
       warn() functions.

       Always be sure to use the proper secure idiom:

	 err(1, "%s", string);

       See attributes(5) for descriptions of the following attributes:

       │Interface Stability │ Committed		   │
       │MT-Level	    │ Safe with Exceptions │

       These  functions	 are safe to use in multithreaded applications as long
       as setlocale(3C) is not being called to change the locale.

       exit(3C), getexecname(3C), setlocale(3C), strerror(3C), attributes(5)

				 Aug 20, 2007			       ERR(3C)

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