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


       #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, ...);

       #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);


       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  a  code  or the global
       variable errno, preceded by another colon  and  space  unless  the  fmt
       argument is NULL.

       The  err(),  verr(),  warn(),  and  vwarn()  functions  use  the global
       variable errno to look up the error message.

       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.


       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);


       These functions are nonstandard BSD extensions.


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


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