(Royal Institute of Technology, Stockholm, Sweden).
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
3. Neither the name of the Institute nor the names of its contributors
may be used to endorse or promote products derived from this software
without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.
$Id$
This manpage was contributed by Gregory McGarry.
.Dd July 7, 2005 .Dt COM_ERR 3 .Os .Sh NAME .Nm com_err , .Nm com_err_va , .Nm error_message , .Nm error_table_name , .Nm init_error_table , .Nm set_com_err_hook , .Nm reset_com_err_hook , .Nm add_to_error_table , .Nm initialize_error_table_r .Nm free_error_table , .Nm com_right .Nd common error display library .Sh LIBRARY Common Error Library (libcom_err, -lcom_err) .Sh SYNOPSIS .Fd #include <stdio.h> .Fd #include <stdarg.h> .Fd #include <com_err.h> .Fd #include "XXX_err.h"
p typedef void (*errf)(const char *, long, const char *, ...); .Ft void .Fn com_err "const char *whoami" "long code" "const char *format" "..." .Ft void .Fn com_err_va "const char *whoami" "long code" "const char *format" "..." .Ft const char * .Fn error_message "long code" .Ft const char * .Fn error_table_name "int num" .Ft int .Fn init_error_table "const char **msgs" "long base" "int count" .Ft errf .Fn set_com_err_hook "errf func" .Ft errf .Fn reset_com_err_hook "" .Ft void .Fn add_to_error_table "struct et_list *new_table" .Ft void .Fn initialize_error_table_r "struct et_list **et_list" "const char **msgs" "int base" "long count" .Ft void .Fn free_error_table "struct et_list *" .Ft const char * .Fn com_right "struct et_list *list" long code" .Sh DESCRIPTION The .Nm library provides a common error-reporting mechanism for defining and accessing error codes and descriptions for application software packages. Error descriptions are defined in a table and error codes are used to index the table. The error table, the descriptions and the error codes are generated using .Xr compile_et 1 .
p The error table is registered with the .Nm library by calling its initialisation function defined in its header file. The initialisation function is generally defined as .Fn initialize_<name>_error_table , where .Em name is the name of the error table.
p If a thread-safe version of the library is needed .Fn initialize_<name>_error_table_r that internally calls .Fn initialize_error_table_r instead be used.
p Any variable which is to contain an error code should be declared .Em <name>_error_number where .Em name is the name of the error table. .Sh FUNCTIONS The following functions are available to the application developer: l -tag -width compact t Fn com_err "whoami" "code" "format" "..." Displays an error message on standard error composed of the .Fa whoami string, which should specify the program name, followed by an error message generated from .Fa code , and a string produced using the .Xr printf 3 .Fa format string and any following arguments. If .Fa format is NULL, the formatted message will not be printed. The argument .Fa format may not be omitted. t Fn com_err_va "whoami" "code" "format" "va_list args" This routine provides an interface, equivalent to .Fn com_err , which may be used by higher-level variadic functions (functions which accept variable numbers of arguments). t Fn error_message "code" Returns the character string error message associate with .Fa code . If .Fa code is associated with an unknown error table, or if .Fa code is associated with a known error table but is not in the table, a string of the form `Unknown code XXXX NN' is returned, where XXXX is the error table name produced by reversing the compaction performed on the error table number implied by that error code, and NN is the offset from that base value.
p Although this routine is available for use when needed, its use should be left to circumstances which render .Fn com_err unusable.
p .Fn com_right returns the error string just like .Fa com_err but in a thread-safe way.
p t Fn error_table_name "num" Convert a machine-independent error table number .Fa num into an error table name. t Fn init_error_table "msgs" "base" "count" Initialise the internal error table with the array of character string error messages in .Fa msgs of length .Fa count . The error codes are assigned incrementally from .Fa base . This function is useful for using the error-reporting mechanism with custom error tables that have not been generated with .Xr compile_et 1 . Although this routine is available for use when needed, its use should be restricted.
p .Fn initialize_error_table_r initialize the .Fa et_list in the same way as .Fn init_error_table , but in a thread-safe way.
p t Fn set_com_err_hook "func" Provides a hook into the .Nm library to allow the routine .Fa func to be dynamically substituted for .Fn com_err . After .Fn set_com_err_hook has been called, calls to .Fn com_err will turn into calls to the new hook routine. This function is intended to be used in daemons to use a routine which calls .Xr syslog 3 , or in a window system application to pop up a dialogue box. t Fn reset_com_err_hook "" Turns off the hook set in .Fn set_com_err_hook . t Fn add_to_error_table "new_table" Add the error table, its messages strings and error codes in .Fa new_table to the internal error table. .El .Sh EXAMPLES The following is an example using the table defined in .Xr compile_et 1 :
p d -literal #include <stdio.h> #include <stdarg.h> #include <syslog.h> #include "test_err.h" void hook(const char *whoami, long code, const char *format, va_list args) { char buffer[BUFSIZ]; static int initialized = 0; if (!initialized) { openlog(whoami, LOG_NOWAIT, LOG_DAEMON); initialized = 1; } vsprintf(buffer, format, args); syslog(LOG_ERR, "%s %s", error_message(code), buffer); } int main(int argc, char *argv[]) { char *whoami = argv[0]; initialize_test_error_table(); com_err(whoami, TEST_INVAL, "before hook"); set_com_err_hook(hook); com_err(whoami, TEST_IO, "after hook"); return (0); } .Ed .Sh SEE ALSO .Xr compile_et 1