ERRC(3bsd) | 3bsd | ERRC(3bsd) |
NAME¶
errc
, verrc
,
warnc
, vwarnc
—
LIBRARY¶
library “libbsd”SYNOPSIS¶
#include <err.h>
(See
libbsd(7) for include usage.)
void
errc
(int
status, int code,
const char *fmt,
...);
void
verrc
(int
status, int code,
const char *fmt,
va_list args);
void
warnc
(int
code, const char
*fmt, ...);
void
vwarnc
(int
code, const char
*fmt, va_list
args);
DESCRIPTION¶
Theerr
() 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, followed by a colon
(‘:’) character and a space, are output. The text that follows
depends on the function being called. The fmt
specification (and associated arguments) may be any format allowed by
printf(3) or NULL
. If the
fmt argument is not NULL
, the
formatted error message is output.
The functions all output an error message string affiliated with
an error value (see strerror(3)), preceded by a colon
character and a space if fmt is not
NULL
. That is, the output is as follows:
progname: fmt: error message string
if fmt is not NULL
,
or:
progname: error message string
if it is.
The argument code is used as the error value instead of the current value of the global variable errno.
In all cases, the output is followed by a newline character.
The errc
(), and
verrc
() functions do not return, but exit with the
value of the argument status.
EXAMPLES¶
Display the current errno information string and exit:if ((p = malloc(size)) == NULL) err(1, NULL); if ((fd = open(file_name, O_RDONLY, 0)) == -1) err(1, "%s", file_name);
Display an error message and exit:
if (tm.tm_hour < START_TIME) errx(1, "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) err(1, "%s", block_device);
SEE ALSO¶
err(3) exit(3), perror(3), printf(3), strerror(3)HISTORY¶
The functionserrc
(), verrc
(),
warnc
(), and vwarnc
() first
appeared in FreeBSD 3.0, NetBSD
7.0 and OpenBSD 5.6.
CAVEATS¶
It is important never to pass a string with user-supplied data as a format without using ‘%s
’. An attacker can put
format specifiers in the string to mangle the stack, leading to a possible
security hole. This holds true even if the string has been built “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
() family of functions.
Always be sure to use the proper secure idiom:
errc(1, 0, "%s", string);
April 23, 2014 | Linux 4.19.0-14-amd64 |