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From: @(#)err.3 8.1 (Berkeley) 6/9/93
$FreeBSD: head/lib/libc/gen/err.3 79531 2001-07-10 13:41:46Z ru $
.Dd March 6, 1999 .Dt ERR 3 .Os .Sh NAME .Nm err , .Nm verr , .Nm errc , .Nm verrc , .Nm errx , .Nm verrx , .Nm warn , .Nm vwarn , .Nm warnc , .Nm vwarnc , .Nm warnx , .Nm vwarnx , .Nm err_set_exit , .Nm err_set_file .Nd formatted error messages .Sh LIBRARY .Lb libc .Sh SYNOPSIS .Fd #include <err.h> .Ft void .Fn err "int eval" "const char *fmt" "..." .Ft void .Fn err_set_exit "void (*exitf)(int)" .Ft void .Fn err_set_file "void *vfp" .Ft void .Fn errc "int eval" "int code" "const char *fmt" "..." .Ft void .Fn errx "int eval" "const char *fmt" "..." .Ft void .Fn warn "const char *fmt" "..." .Ft void .Fn warnc "int code" "const char *fmt" "..." .Ft void .Fn warnx "const char *fmt" "..." .Fd #include <stdarg.h> .Ft void .Fn verr "int eval" "const char *fmt" "va_list args" .Ft void .Fn verrc "int eval" "int code" "const char *fmt" "va_list args" .Ft void .Fn verrx "int eval" "const char *fmt" "va_list args" .Ft void .Fn vwarn "const char *fmt" "va_list args" .Ft void .Fn vwarnc "int code" "const char *fmt" "va_list args" .Ft void .Fn vwarnx "const char *fmt" "va_list args" .Sh DESCRIPTION The .Fn err and .Fn warn family of functions display a formatted error message on the standard error output, or on another file specified using the .Fn err_set_file function. In all cases, the last component of the program name, a colon character, and a space are output. If the .Fa fmt argument is not NULL, the .Xr printf 3 -like formatted error message is output. The output is terminated by a newline character.
p The .Fn err , .Fn errc , .Fn verr , .Fn verrc , .Fn warn , .Fn warnc , .Fn vwarn , and .Fn vwarnc functions append an error message obtained from .Xr strerror 3 based on a code or the global variable .Va errno , preceded by another colon and space unless the .Fa fmt argument is .Dv NULL .
p In the case of the .Fn errc , .Fn verrc , .Fn warnc , and .Fn vwarnc functions, the .Fa code argument is used to look up the error message.
p The .Fn err , .Fn verr , .Fn warn , and .Fn vwarn functions use the global variable .Va errno to look up the error message.
p The .Fn errx and .Fn warnx functions do not append an error message.
p The .Fn err , .Fn verr , .Fn errc , .Fn verrc , .Fn errx , and .Fn verrx functions do not return, but exit with the value of the argument .Fa eval . The .Fn err_set_exit function can be used to specify a function which is called before .Xr exit 3 to perform any necessary cleanup; passing a null function pointer for .Va exitf resets the hook to do nothing. The .Fn err_set_file function sets the output stream used by the other functions. Its .Fa 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). .Sh EXAMPLES Display the current errno information string and exit: d -literal -offset indent if ((p = malloc(size)) == NULL) err(1, NULL); if ((fd = open(file_name, O_RDONLY, 0)) == -1) err(1, "%s", file_name); .Ed
p Display an error message and exit: d -literal -offset indent if (tm.tm_hour < START_TIME) errx(1, "too early, wait until %s", start_time_string); .Ed
p Warn of an error: d -literal -offset indent 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); .Ed
p Warn of an error without using the global variable .Va errno : d -literal -offset indent error = my_function(); /* returns a value from <errno.h> */ if (error != 0) warnc(error, "my_function"); .Ed .Sh SEE ALSO .Xr exit 3 , .Xr printf 3 , .Xr strerror 3 .Sh HISTORY The .Fn err and .Fn warn functions first appeared in x 4.4 . The .Fn err_set_exit and .Fn err_set_file functions first appeared in .Fx 2.1 . The .Fn errc and .Fn warnc functions first appeared in .Fx 3.0 .