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


       #include <err.h>

       noreturn void err(int eval, const char *fmt, ...);
       noreturn void errx(int eval, const char *fmt, ...);

       void warn(const char *fmt, ...);
       void warnx(const char *fmt, ...);

       #include <stdarg.h>

       noreturn void verr(int eval, const char *fmt, va_list args);
       noreturn 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);


       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 printf(3)-like formatted
       error message is output.  The output is terminated by a newline character.

       The err(), verr(), warn(), and vwarn() functions append an  error  message  obtained  from
       strerror(3) based on the global variable errno, preceded by another colon and space unless
       the fmt argument is NULL.

       The errx() and warnx() functions do not append an error message.

       The err(), verr(), errx(), and verrx() functions do not return, but exit with the value of
       the argument eval.


       For an explanation of the terms used in this section, see attributes(7).

       │InterfaceAttributeValue          │
       │err(), errx(), warn(), warnx(), verr(), verrx(),        │ Thread safety │ MT-Safe locale │
       │vwarn(), vwarnx()                                       │               │                │


       These functions are nonstandard BSD extensions.


       Display the current errno information string and exit:

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

       Display an error message and exit:

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

       Warn of an error:

           fd = open(raw_device, O_RDONLY, 0);
           if (fd == -1)
               warnx("%s: %s: trying the block device",
                       raw_device, strerror(errno));
           fd = open(block_device, O_RDONLY, 0);
           if (fd == -1)
               err(EXIT_FAILURE, "%s", block_device);


       error(3), exit(3), perror(3), printf(3), strerror(3)


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