错误信息：
: undefined reference to `err_quit'
: undefined reference to `err_sys'
解决方法：
因为err_quit跟err_sys是作者自己定义的错误处理函数。所以最简单的解决办法是修改下apue.h文件，如下
/* * Our own header, to be included before all standard system headers. */ #ifndef _APUE_H #define _APUE_H #define _POSIX_C_SOURCE 200809L #if defined(SOLARIS) /* Solaris 10 */ #define _XOPEN_SOURCE 600 #else #define _XOPEN_SOURCE 700 #endif #include <sys/types.h> /* some systems still require this */ #include <sys/stat.h> #include <sys/termios.h> /* for winsize */ #if defined(MACOS) || !defined(TIOCGWINSZ) #include <sys/ioctl.h> #endif #include <stdio.h> /* for convenience */ #include <stdlib.h> /* for convenience */ #include <stddef.h> /* for offsetof */ #include <string.h> /* for convenience */ #include <unistd.h> /* for convenience */ #include <signal.h> /* for SIG_ERR */ #include <errno.h> #include <stdarg.h> #define MAXLINE 4096 /* max line length */ /* * Default file access permissions for new files. */ #define FILE_MODE (S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH) /* * Default permissions for new directories. */ #define DIR_MODE (FILE_MODE | S_IXUSR | S_IXGRP | S_IXOTH) typedef void Sigfunc(int); /* for signal handlers */ #define min(a,b) ((a) < (b) ? (a) : (b)) #define max(a,b) ((a) > (b) ? (a) : (b)) /* * Prototypes for our own functions. */ char *path_alloc(size_t *); /* {Prog pathalloc} */ long open_max(void); /* {Prog openmax} */ int set_cloexec(int); /* {Prog setfd} */ void clr_fl(int, int); void set_fl(int, int); /* {Prog setfl} */ void pr_exit(int); /* {Prog prexit} */ void pr_mask(const char *); /* {Prog prmask} */ Sigfunc *signal_intr(int, Sigfunc *); /* {Prog signal_intr_function} */ void daemonize(const char *); /* {Prog daemoninit} */ void sleep_us(unsigned int); /* {Ex sleepus} */ ssize_t readn(int, void *, size_t); /* {Prog readn_writen} */ ssize_t writen(int, const void *, size_t); /* {Prog readn_writen} */ int fd_pipe(int *); /* {Prog sock_fdpipe} */ int recv_fd(int, ssize_t (*func)(int, const void *, size_t)); /* {Prog recvfd_sockets} */ int send_fd(int, int); /* {Prog sendfd_sockets} */ int send_err(int, int, const char *); /* {Prog senderr} */ int serv_listen(const char *); /* {Prog servlisten_sockets} */ int serv_accept(int, uid_t *); /* {Prog servaccept_sockets} */ int cli_conn(const char *); /* {Prog cliconn_sockets} */ int buf_args(char *, int (*func)(int, char **)); /* {Prog bufargs} */ int tty_cbreak(int); /* {Prog raw} */ int tty_raw(int); /* {Prog raw} */ int tty_reset(int); /* {Prog raw} */ void tty_atexit(void); /* {Prog raw} */ struct termios *tty_termios(void); /* {Prog raw} */ int ptym_open(char *, int); /* {Prog ptyopen} */ int ptys_open(char *); /* {Prog ptyopen} */ #ifdef TIOCGWINSZ pid_t pty_fork(int *, char *, int, const struct termios *, const struct winsize *); /* {Prog ptyfork} */ #endif int lock_reg(int, int, int, off_t, int, off_t); /* {Prog lockreg} */ #define read_lock(fd, offset, whence, len) lock_reg((fd), F_SETLK, F_RDLCK, (offset), (whence), (len)) #define readw_lock(fd, offset, whence, len) lock_reg((fd), F_SETLKW, F_RDLCK, (offset), (whence), (len)) #define write_lock(fd, offset, whence, len) lock_reg((fd), F_SETLK, F_WRLCK, (offset), (whence), (len)) #define writew_lock(fd, offset, whence, len) lock_reg((fd), F_SETLKW, F_WRLCK, (offset), (whence), (len)) #define un_lock(fd, offset, whence, len) lock_reg((fd), F_SETLK, F_UNLCK, (offset), (whence), (len)) pid_t lock_test(int, int, off_t, int, off_t); /* {Prog locktest} */ #define is_read_lockable(fd, offset, whence, len) (lock_test((fd), F_RDLCK, (offset), (whence), (len)) == 0) #define is_write_lockable(fd, offset, whence, len) (lock_test((fd), F_WRLCK, (offset), (whence), (len)) == 0) void err_msg(const char *, ...); /* {App misc_source} */ void err_dump(const char *, ...) __attribute__((noreturn)); void err_quit(const char *, ...) __attribute__((noreturn)); void err_cont(int, const char *, ...); void err_exit(int, const char *, ...) __attribute__((noreturn)); void err_ret(const char *, ...); void err_sys(const char *, ...) __attribute__((noreturn)); void log_msg(const char *, ...); /* {App misc_source} */ void log_open(const char *, int, int); void log_quit(const char *, ...) __attribute__((noreturn)); void log_ret(const char *, ...); void log_sys(const char *, ...) __attribute__((noreturn)); void log_exit(int, const char *, ...) __attribute__((noreturn)); void TELL_WAIT(void); /* parent/child from {Sec race_conditions} */ void TELL_PARENT(pid_t); void TELL_CHILD(pid_t); void WAIT_PARENT(void); void WAIT_CHILD(void); static void err_doit(int, int, const char *, va_list); /* * * Nonfatal error related to a system call. * * Print a message and return. * */ void err_ret(const char *fmt, ...) { va_list ap; va_start(ap, fmt); err_doit(1, errno, fmt, ap); va_end(ap); } /* * * Fatal error related to a system call. * * Print a message and terminate. * */ void err_sys(const char *fmt, ...) { va_list ap; va_start(ap, fmt); err_doit(1, errno, fmt, ap); va_end(ap); exit(1); } /* * * Fatal error unrelated to a system call. * * Error code passed as explict parameter. * * Print a message and terminate. * */ void err_exit(int error, const char *fmt, ...) { va_list ap; va_start(ap, fmt); err_doit(1, error, fmt, ap); va_end(ap); exit(1); } /* * * Fatal error related to a system call. * * Print a message, dump core, and terminate. * */ void err_dump(const char *fmt, ...) { va_list ap; va_start(ap, fmt); err_doit(1, errno, fmt, ap); va_end(ap); abort(); /* dump core and terminate */ exit(1); /* shouldn't get here */ } /* * * Nonfatal error unrelated to a system call. * * Print a message and return. * */ void err_msg(const char *fmt, ...) { va_list ap; va_start(ap, fmt); err_doit(0, 0, fmt, ap); va_end(ap); } /* * * Fatal error unrelated to a system call. * * Print a message and terminate. * */ void err_quit(const char *fmt, ...) { va_list ap; va_start(ap, fmt); err_doit(0, 0, fmt, ap); va_end(ap); exit(1); } /* * * Print a message and return to caller. * * Caller specifies "errnoflag". * */ static void err_doit(int errnoflag, int error, const char *fmt, va_list ap) { char buf[MAXLINE]; vsnprintf(buf, MAXLINE, fmt, ap); if (errnoflag) snprintf(buf+strlen(buf), MAXLINE-strlen(buf), ": %s",strerror(error)); strcat(buf, " "); fflush(stdout); /* in case stdout and stderr are the same */ fputs(buf, stderr); fflush(NULL); /* flushes all stdio output streams */ } #endif /* _APUE_H */