lib/error_functions.c

This is lib/error_functions.c (Listing 3-3, page 54), an example program file from the book, The Linux Programming Interface.

The source code file is copyright 2010, Michael Kerrisk, and is licensed under the GNU Lesser General Public License, version 3.

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In the listing below, the names of Linux system calls and C library functions are hyperlinked to manual pages from the Linux man-pages project, and the names of functions implemented in the book are hyperlinked to the implementations of those functions.

  Cover of The Linux Programming Interface

Function list (Bold in this list means a function is not static)

/* error_functions.c

   Some standard error handling routines used by various programs.
*/
#include <stdarg.h>
#include "error_functions.h"
#include "tlpi_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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