err(3) - Linux manual page (original) (raw)

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)](../man3/printf.3.html)-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)](../man3/strerror.3.html) based on the global variable
   _[errno](../man3/errno.3.html)_, 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
   [attributes(7)](../man7/attributes.7.html).
   ┌───────────────────────────────┬───────────────┬────────────────┐
   │ **Interface** │ **Attribute** │ **Value** │
   ├───────────────────────────────┼───────────────┼────────────────┤
   │ **err**(), **errx**(), **warn**(),        │ Thread safety │ MT-Safe locale │
   │ **warnx**(), **verr**(), **verrx**(),     │               │                │
   │ **vwarn**(), **vwarnx**()             │               │                │
   └───────────────────────────────┴───────────────┴────────────────┘

STANDARDS top

   BSD.

HISTORY top

   **err**()
   **warn**() 4.4BSD.

EXAMPLES top

   Display the current _[errno](../man3/errno.3.html)_ 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 top

   [error(3)](../man3/error.3.html), [exit(3)](../man3/exit.3.html), [perror(3)](../man3/perror.3.html), [printf(3)](../man3/printf.3.html), [strerror(3)](../man3/strerror.3.html)

COLOPHON top

   This page is part of the _man-pages_ (Linux kernel and C library
   user-space interface documentation) project.  Information about
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   for this manual page, see
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   2025-02-02.  If you discover any rendering problems in this HTML
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   part of the original manual page), send a mail to
   man-pages@man7.org

Linux man-pages 6.10 2024-07-23 err(3)

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