err(3) — Linux manual page


err(3)                  Library Functions Manual                  err(3)

NAME         top

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

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #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         top

       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         top

       For an explanation of the terms used in this section, see
       │ Interface                    Attribute     Value          │
       │ err(), errx(), warn(),       │ Thread safety │ MT-Safe locale │
       │ warnx(), verr(), verrx(),    │               │                │
       │ vwarn(), vwarnx()            │               │                │

STANDARDS         top


HISTORY         top

       warn() 4.4BSD.

EXAMPLES         top

       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);

SEE ALSO         top

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

COLOPHON         top

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

Pages that refer to this page: errno(3)error(3)perror(3)strerror(3)sysexits.h(3head)