lib/error_functions.cThis is lib/error_functions.c (Listing 3-3, page 54), an example from the book, The Linux Programming Interface. The source code file is copyright 2024, Michael Kerrisk, and is licensed under the GNU Lesser General Public License, version 3. This page shows the "distribution" or "book" version of the file (why are there two versions?), or the differences between the two versions. You can switch between the views using the tabs below. 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.
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#include <stdarg.h> #include "error_functions.h" #include "tlpi_hdr.h" #include "ename.c.inc" /* Defines ename and MAX_ENAME */
NORETURN 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); }
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 */ }
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; }
void errExit(const char *format, ...) { va_list argList; va_start(argList, format); outputError(TRUE, errno, TRUE, format, argList); va_end(argList); terminate(TRUE); }
void err_exit(const char *format, ...) { va_list argList; va_start(argList, format); outputError(TRUE, errno, FALSE, format, argList); va_end(argList); terminate(FALSE); }
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); }
void fatal(const char *format, ...) { va_list argList; va_start(argList, format); outputError(FALSE, 0, TRUE, format, argList); va_end(argList); terminate(TRUE); }
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); }
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); }
Note that, in most cases, the programs rendered in these web pages are not free standing: you'll typically also need a few other source files (mostly in the lib/ subdirectory) as well. Generally, it's easier to just download the entire source tarball and build the programs with make(1). By hovering your mouse over the various hyperlinked include files and function calls above, you can see which other source files this file depends on.