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/*************************************************************************\
* Copyright (C) Michael Kerrisk, 2018. *
* *
* This program is free software. You may use, modify, and redistribute it *
* under the terms of the GNU Lesser General Public License as published *
* by the Free Software Foundation, either version 3 or (at your option) *
* any later version. This program is distributed without any warranty. *
* See the files COPYING.lgpl-v3 and COPYING.gpl-v3 for details. *
\*************************************************************************/
/* Listing 3-3 */
/* error_functions.c
Some standard error handling routines used by various programs.
*/
#include <stdarg.h>
#include "error_functions.h"
#include "af_unix_hdr.h"
#include "ename.c.inc" /* Defines ename and MAX_ENAME */
#ifdef __GNUC__ /* Prevent 'gcc -Wall' complaining */
__attribute__ ((__noreturn__)) /* if we call this function as last */
#endif /* statement in a non-void function */
static void
terminate(Boolean useExit3)
{
char *s;
/* Dump core if EF_DUMPCORE environment variable is defined and
is a nonempty string; otherwise call exit(3) or _exit(2),
depending on the value of 'useExit3'. */
s = getenv("EF_DUMPCORE");
if (s != NULL && *s != '\0')
abort();
else if (useExit3)
exit(EXIT_FAILURE);
else
_exit(EXIT_FAILURE);
}
/* Diagnose 'errno' error by:
* outputting a string containing the error name (if available
in 'ename' array) corresponding to the value in 'err', along
with the corresponding error message from strerror(), and
* outputting the caller-supplied error message specified in
'format' and 'ap'. */
static void
outputError(Boolean useErr, int err, Boolean flushStdout,
const char *format, va_list ap)
{
#define BUF_SIZE 500
char buf[BUF_SIZE], userMsg[BUF_SIZE], errText[BUF_SIZE];
vsnprintf(userMsg, BUF_SIZE, format, ap);
if (useErr)
snprintf(errText, BUF_SIZE, " [%s %s]",
(err > 0 && err <= MAX_ENAME) ?
ename[err] : "?UNKNOWN?", strerror(err));
else
snprintf(errText, BUF_SIZE, ":");
snprintf(buf, BUF_SIZE, "ERROR%s %s\n", errText, userMsg);
if (flushStdout)
fflush(stdout); /* Flush any pending stdout */
fputs(buf, stderr);
fflush(stderr); /* In case stderr is not line-buffered */
}
/* Display error message including 'errno' diagnostic, and
return to caller */
void
errMsg(const char *format, ...)
{
va_list argList;
int savedErrno;
savedErrno = errno; /* In case we change it here */
va_start(argList, format);
outputError(TRUE, errno, TRUE, format, argList);
va_end(argList);
errno = savedErrno;
}
/* Display error message including 'errno' diagnostic, and
terminate the process */
void
errExit(const char *format, ...)
{
va_list argList;
va_start(argList, format);
outputError(TRUE, errno, TRUE, format, argList);
va_end(argList);
terminate(TRUE);
}
/* Display error message including 'errno' diagnostic, and
terminate the process by calling _exit().
The relationship between this function and errExit() is analogous
to that between _exit(2) and exit(3): unlike errExit(), this
function does not flush stdout and calls _exit(2) to terminate the
process (rather than exit(3), which would cause exit handlers to be
invoked).
These differences make this function especially useful in a library
function that creates a child process that must then terminate
because of an error: the child must terminate without flushing
stdio buffers that were partially filled by the caller and without
invoking exit handlers that were established by the caller. */
void
err_exit(const char *format, ...)
{
va_list argList;
va_start(argList, format);
outputError(TRUE, errno, FALSE, format, argList);
va_end(argList);
terminate(FALSE);
}
/* The following function does the same as errExit(), but expects
the error number in 'errnum' */
void
errExitEN(int errnum, const char *format, ...)
{
va_list argList;
va_start(argList, format);
outputError(TRUE, errnum, TRUE, format, argList);
va_end(argList);
terminate(TRUE);
}
/* Print an error message (without an 'errno' diagnostic) */
void
fatal(const char *format, ...)
{
va_list argList;
va_start(argList, format);
outputError(FALSE, 0, TRUE, format, argList);
va_end(argList);
terminate(TRUE);
}
/* Print a command usage error message and terminate the process */
void
usageErr(const char *format, ...)
{
va_list argList;
fflush(stdout); /* Flush any pending stdout */
fprintf(stderr, "Usage: ");
va_start(argList, format);
vfprintf(stderr, format, argList);
va_end(argList);
fflush(stderr); /* In case stderr is not line-buffered */
exit(EXIT_FAILURE);
}
/* Diagnose an error in command-line arguments and
terminate the process */
void
cmdLineErr(const char *format, ...)
{
va_list argList;
fflush(stdout); /* Flush any pending stdout */
fprintf(stderr, "Command-line usage error: ");
va_start(argList, format);
vfprintf(stderr, format, argList);
va_end(argList);
fflush(stderr); /* In case stderr is not line-buffered */
exit(EXIT_FAILURE);
}
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