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err(3) — Linux manual page

err(3)                   Library Functions Manualerr(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(inteval, const char *fmt, ...);[[noreturn]] void errx(inteval, const char *fmt, ...);void warn(const char *fmt, ...);void warnx(const char *fmt, ...);#include <stdarg.h>[[noreturn]] void verr(inteval, const char *fmt, va_listargs);[[noreturn]] void verrx(inteval, const char *fmt, va_listargs);void vwarn(const char *fmt, va_listargs);void vwarnx(const char *fmt, va_listargs);

DESCRIPTION        top

       Theerr() andwarn() 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 thefmt argument is not NULL, theprintf(3)-like       formatted error message is output.  The output is terminated by a       newline character.       Theerr(),verr(),warn(), andvwarn() functions append an error       message obtained fromstrerror(3) based on the global variableerrno, preceded by another colon and space unless thefmt argument       is NULL.       Theerrx() andwarnx() functions do not append an error message.       Theerr(),verr(),errx(), andverrx() functions do not return,       but exit with the value of the argumenteval.

ATTRIBUTES        top

       For an explanation of the terms used in this section, seeattributes(7).       ┌───────────────────────────────┬───────────────┬────────────────┐       │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 currenterrno 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),exit(3),perror(3),printf(3),strerror(3)

COLOPHON        top

       This page is part of theman-pages (Linux kernel and C library       user-space interface documentation) project.  Information about       the project can be found at        ⟨https://www.kernel.org/doc/man-pages/⟩.  If you have a bug report       for this manual page, see       ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.       This page was obtained from the tarball man-pages-6.15.tar.gz       fetched from       ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on       2025-08-11.  If you discover any rendering problems in this HTML       version of the page, or you believe there is a better or more up-       to-date source for the page, or you have corrections or       improvements to the information in this COLOPHON (which isnot       part of the original manual page), send a mail to       man-pages@man7.orgLinux man-pages 6.15            2025-05-17err(3)

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

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