err(3)                     Library Functions Manual                     err(3)

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

LIBRARY
       Standard C library (libc, -lc)

SYNOPSIS
       #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);

DESCRIPTION
       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.

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

       +-------------------------------------+---------------+----------------+
       |Interface                            | Attribute     | Value          |
       +-------------------------------------+---------------+----------------+
       |err (), errx (), warn (), warnx (),  | Thread safety | MT-Safe locale |
       |verr (), verrx (), vwarn (), vwarnx  |               |                |
       |()                                   |               |                |
       +-------------------------------------+---------------+----------------+
STANDARDS
       BSD.

HISTORY
       err()
       warn() 4.4BSD.

EXAMPLES
       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);

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

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