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download PDF document: vwarnc.3.pdf

ERR(3) FreeBSD Library Functions Manual ERR(3)
NAME err, verr, errc, verrc, errx, verrx, warn, vwarn, warnc, vwarnc, warnx, vwarnx, err_set_exit, err_set_file - formatted error messages
LIBRARY Standard C Library (libc, -lc)
SYNOPSIS #include <err.h>
void err(int eval, const char *fmt, ...);
void err_set_exit(void (*exitf)(int));
void err_set_file(void *vfp);
void errc(int eval, int code, const char *fmt, ...);
void errx(int eval, const char *fmt, ...);
void warn(const char *fmt, ...);
void warnc(int code, const char *fmt, ...);
void warnx(const char *fmt, ...);
#include <stdarg.h>
void verr(int eval, const char *fmt, va_list args);
void verrc(int eval, int code, const char *fmt, va_list args);
void verrx(int eval, const char *fmt, va_list args);
void vwarn(const char *fmt, va_list args);
void vwarnc(int code, const char *fmt, va_list args);
void vwarnx(const char *fmt, va_list args);
DESCRIPTION The err() and warn() family of functions display a formatted error message on the standard error output, or on another file specified using based on a supplied error code value or the global variable errno, preceded by another colon and space unless the fmt argument is NULL.
In the case of the errc(), verrc(), warnc(), and vwarnc() functions, the code argument is used to look up the error message.
The err(), verr(), warn(), and vwarn() functions use the global variable errno to look up the error message.
The errx() and warnx() functions do not append an error message.
The err(), verr(), errc(), verrc(), errx(), and verrx() functions do not return, but exit with the value of the argument eval. It is recommended that the standard values defined in sysexits(3) be used for the value of eval. The err_set_exit() function can be used to specify a function which is called before exit(3) to perform any necessary cleanup; passing a null function pointer for exitf resets the hook to do nothing. The err_set_file() function sets the output stream used by the other functions. Its vfp argument must be either a pointer to an open stream (possibly already converted to void *) or a null pointer (in which case the output stream is set to standard error).
EXAMPLES Display the current errno information string and exit:
if ((p = malloc(size)) == NULL) err(EX_OSERR, NULL); if ((fd = open(file_name, O_RDONLY, 0)) == -1) err(EX_NOINPUT, "%s", file_name);
Display an error message and exit:
if (tm.tm_hour < START_TIME) errx(EX_DATAERR, "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(EX_OSFILE, "%s", block_device);
Warn of an error without using the global variable errno:
error = my_function(); /* returns a value from <errno.h> */ if (error != 0) warnc(error, "my_function");
SEE ALSO exit(3), fmtmsg(3), printf(3), strerror(3), sysexits(3)
STANDARDS The err() and warn() families of functions are BSD extensions. As such they should not be used in truly portable code. Use strerror() or similar functions instead.
HISTORY