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

       For an explanation of the terms used in this section, see attributes(7).
       ┌──────────────────────────────────────────────────────────────────────┬───────────────┬────────────────┐
       │ Interface                                                            │ Attribute     │ Value          │
       ├──────────────────────────────────────────────────────────────────────┼───────────────┼────────────────┤
       │ err(), errx(), warn(), warnx(), verr(), verrx(), vwarn(), vwarnx()   │ Thread safety │ MT-Safe locale │
       └──────────────────────────────────────────────────────────────────────┴───────────────┴────────────────┘

       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.

       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",
                       start_time_string);

       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);

err()
       warn() 4.4BSD.

       Standard C library (libc, -lc)

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

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

Linux man-pages 6.9.1                              2024-05-02                                             err(3)

       BSD.

#include<err.h>[[noreturn]]voiderr(inteval,constchar*fmt,...);[[noreturn]]voiderrx(inteval,constchar*fmt,...);voidwarn(constchar*fmt,...);voidwarnx(constchar*fmt,...);#include<stdarg.h>[[noreturn]]voidverr(inteval,constchar*fmt,va_listargs);[[noreturn]]voidverrx(inteval,constchar*fmt,va_listargs);voidvwarn(constchar*fmt,va_listargs);voidvwarnx(constchar*fmt,va_listargs);