ERR(3) | Library Functions Manual | ERR(3) |
err
, verr
,
errx
, verrx
,
errc
, verrc
,
warn
, vwarn
,
warnx
, vwarnx
,
warnc
, vwarnc
—
#include <err.h>
void
err
(int
status, const char
*fmt, ...);
void
verr
(int
status, const char
*fmt, va_list
args);
void
errx
(int
status, const char
*fmt, ...);
void
verrx
(int
status, const char
*fmt, va_list
args);
void
errc
(int
status, int code,
const char *fmt,
...);
void
verrc
(int
status, int code,
const char *fmt,
va_list args);
void
warn
(const
char *fmt,
...);
void
vwarn
(const
char *fmt, va_list
args);
void
warnx
(const
char *fmt,
...);
void
vwarnx
(const
char *fmt, va_list
args);
void
warnc
(int
code, const char
*fmt, ...);
void
vwarnc
(int
code, const char
*fmt, va_list
args);
err
() and warn
() family of
functions display a formatted error message on the standard error output.
In all cases these functions output the last component of the
program name, a colon character, and a space. If the
fmt argument is not NULL
, it
is used as a printf(3)-like
format specification for the error message.
In the case of the err
(),
verr
(), warn
(), and
vwarn
() functions, an additional error message
string affiliated with the current value of the global variable
errno is output next, preceded by a colon character
and a space if fmt is not
NULL
. The errc
(),
verrc
(), warnc
(), and
vwarnc
() functions take an additional
code argument to be used as the error number instead
of using the global errno variable. The
errx
(), verrx
(),
warnx
(), and vwarnx
()
functions will not output an additional error message string.
In all cases, the output is terminated by a newline character.
The err
(), verr
(),
errc
(), verrc
(),
errx
(), and verrx
()
functions do not return, but instead cause the program to terminate with the
status value given by the argument status. It is often
appropriate to use the value EXIT_FAILURE
, defined
in <stdlib.h>
, as the
status argument given to these functions.
if ((p = malloc(size)) == NULL) err(EXIT_FAILURE, NULL); if ((fd = open(file_name, O_RDONLY, 0)) == -1) err(EXIT_FAILURE, "%s", file_name);
Display an error message and terminate with status indicating failure:
if (tm.tm_hour < START_TIME) errx(EXIT_FAILURE, "too early, wait until %s", start_time_string);
Warn of an error:
if ((fd = open(raw_device, O_RDONLY, 0)) == -1) warnx("%s: %s: trying the block device", raw_device, strerror(errno)); if ((fd = open(block_device, O_RDONLY, 0)) == -1) warn("%s", block_device);
err
() and warn
() functions
first appeared in 4.4BSD. The
errc
() and warnc
() functions
first appeared in FreeBSD 3.0 and
NetBSD 7.0.
%s
’. An attacker can put
format specifiers in the string to mangle your stack, leading to a possible
security hole. This holds true even if you have built the string “by
hand” using a function like snprintf
(), as the
resulting string may still contain user-supplied conversion specifiers for
later interpolation by the err
() and
warn
() functions.
Always be sure to use the proper secure idiom:
err(1, "%s", string);
February 2, 2024 | NetBSD 10.1 |