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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | ATTRIBUTES | STANDARDS | HISTORY | EXAMPLES | SEE ALSO | COLOPHON |
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err(3) Library Functions Manual err(3)
err, verr, errx, verrx, warn, vwarn, warnx, vwarnx - formatted
error messages
Standard C library (libc, -lc)
#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);
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.
For an explanation of the terms used in this section, see
attributes(7).
┌───────────────────────────────┬───────────────┬────────────────┐
│ Interface │ Attribute │ Value │
├───────────────────────────────┼───────────────┼────────────────┤
│ err(), errx(), warn(), │ Thread safety │ MT-Safe locale │
│ warnx(), verr(), verrx(), │ │ │
│ vwarn(), vwarnx() │ │ │
└───────────────────────────────┴───────────────┴────────────────┘
BSD.
err()
warn() 4.4BSD.
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);
error(3), exit(3), perror(3), printf(3), strerror(3)
This page is part of the man-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 is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.15 2025-05-17 err(3)
Pages that refer to this page: errno(3), error(3), perror(3), strerror(3), sysexits.h(3head)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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