第一章：UNIX基础知识

　　本章内容主要是为了学习UNIX的基本知识和一些最基本的系统函数。

　　学习的关键就是跟随者书本敲代码。本节遇到的第一个问题就死本书的apue.h这个文件：一开始没有注意这个文件，盲目的去百度，一番百度之后发现，其实这个文件的源码就在书的附录里面。这个给我一个教训，学习还是静下心来学习，没有一颗安定的心无法学习好，这是个教训啊，以后再也不能犯了。

　　关于apue.h这个文件的源码先贴在本章中便于复制

/* Our own header, to be included before all standard system headers */
    #ifndef _APUE_H
    #define _APUE_H
    #if defined(SOLARIS)
    #define _XOPEN_SOURCE   500     /* Single UNIX Specification, Version 2  for Solaris 9 */
    #define CMSG_LEN(x)     _CMSG_DATA_ALIGN(sizeof(struct cmsghdr)+(x))
    #elif !defined(BSD)
    #define _XOPEN_SOURCE   600     /* Single UNIX Specification, Version 3 */
    #endif
    #include <sys/types.h>          /* some systems still require this */
    #include <sys/stat.h>
    #include <sys/termios.h>        /* for winsize */
    #ifndef 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>
    #include <syslog.h>
    #include <error.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 */
    #if     defined(SIG_IGN) && !defined(SIG_ERR)
    #define SIG_ERR ((Sigfunc *)-1)
    #endif
    #define min(a,b)        ((a) < (b) ? (a) : (b))
    #define max(a,b)        ((a) > (b) ? (a) : (b))
    /*
     * Prototypes for our own functions.
     */
    char    *path_alloc(int *);                             /* {Prog pathalloc} */
    long     open_max(void);                                /* {Prog openmax} */
    void     clr_fl(int, int);                              /* {Prog setfl} */
    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} */
    int              tty_cbreak(int);                               /* {Prog raw} */
    int              tty_raw(int);                                  /* {Prog raw} */
    int              tty_reset(int);                                /* {Prog raw} */
    void     tty_atexit(void);                              /* {Prog raw} */
    #ifdef  ECHO    /* only if <termios.h> has been included */
    struct termios  *tty_termios(void);             /* {Prog raw} */
    #endif
    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} */
    void     daemonize(const char *);                       /* {Prog daemoninit} */
    int              s_pipe(int *);                                 /* {Progs streams_spipe sock_spipe} */
    int              recv_fd(int, ssize_t (*func)(int,
                             const void *, size_t));/* {Progs recvfd_streams recvfd_sockets} */
    int              send_fd(int, int);                             /* {Progs sendfd_streams sendfd_sockets} */
    int              send_err(int, int,
                              const char *);                /* {Prog senderr} */
    int              serv_listen(const char *);             /* {Progs servlisten_streams servlisten_sockets} */
    int              serv_accept(int, uid_t *);             /* {Progs servaccept_streams servaccept_sockets} */
    int              cli_conn(const char *);                /* {Progs cliconn_streams cliconn_sockets} */
    int              buf_args(char *, int (*func)(int,
                              char **));                    /* {Prog bufargs} */
    int              ptym_open(char *, int);        /* {Progs3 ptyopen_streams ptyopen_bsd ptyopen_linux} */
    int              ptys_open(char *);                     /* {Progs3 ptyopen_streams ptyopen_bsd ptyopen_linux} */
    #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_dump(const char *, ...);            /* {App misc_source} */
    void    err_msg(const char *, ...);
    void    err_quit(const char *, ...);
    void    err_exit(int, const char *, ...);
    void    err_ret(const char *, ...);
    void    err_sys(const char *, ...);
    void    log_msg(const char *, ...);                     /* {App misc_source} */
    void    log_open(const char *, int, int);
    void    log_quit(const char *, ...);
    void    log_ret(const char *, ...);
    void    log_sys(const char *, ...);
    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);
    #endif  /* _APUE_H */

　　还有error.c文件的源码也贴出来

#include "apue.h"
#include <errno.h>      /* for definition of errno */
#include <stdarg.h>     /* ISO C variable aruments */
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(, 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(, errno, fmt, ap);
    va_end(ap);
    exit();
}
/*
* 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(, error, fmt, ap);
    va_end(ap);
    exit();
}
/*
* 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(, errno, fmt, ap);
    va_end(ap);
    abort();        /* dump core and terminate */
    exit();        /* 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(, , 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(, , fmt, ap);
    va_end(ap);
    exit();
}
/*
* 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 */
}

最后就是关于代码的编译，直接gcc -o LS.C error.c，目前不会写makefile文件，也就这样将就下，正打算把这些都拿下。