root@HelloWorld:/C# gcc -o PrintPID.out PrintPID.c
PrintPID.c:3: error: expected ‘;’, ‘,’ or ‘)’ before ‘{’ token
root@HelloWorld:/C#

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PrintPID.c如下：
#include "apue.h"
int main(void)
{
printf("Hello world from process ID %d\n", getpid());
exit(0);
}
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apue.h如下：

#ifndef _APUE_H
#define _APUE_H

#define _XOPEN_SOURCE 600

#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
#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 *);
long open_max(void);
void set_fl(int, int);
void clr_fl(int, int);
void pr_exit(int);
void pr_mask(const char*);
Sigfunc *signal_intr(int, Sigfunc *);

int tty_cbreak(int);
int tty_raw(int);
int tty_reset(int);
void tty_atexit(void);
#ifdef ECHO //Only if<termios.h>has bee include
struct termios *tty_termios(void);
#endif

void sleep_us(unsigned int);
ssize_t readn(int, void *, size_t);
ssize_t writen(int, const void *, size_t);
void daemonize(const char *);

int s_pipe(int *);
int recv_fd(int, ssize_t (*func)(int, const void *, size_t));

int send_fd(int, int);
int send_err(int, int, const char*);

int serv_listen(const char*);
int serv_accept(int, uid_t*);
int cli_conn(const char*);
int buf_args(char *, int (*func)(int, char **);

int ptym_open(char *, int);
int ptys_open(char *);
#ifdef TIOCGWINSZ
pid_t pty_fork(int *, char *, int, const struct termios *,
const struct winsize *);
#endif

int lock_reg(int, int, int, off_t, int, off_t);
#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_DLCK, (offset), (whence), (len))
#define writ_lock(fd, offset, whence, len)\
lock_reg((fd), F_SETLK, F_RDLCK, (offset), (whence), (len))
#define writw_lock(fd, offset, whence, len)\
lock_reg((fd), F_SETLKW, F_DLCK, (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);

#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 *, ...);
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 *, ... );
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);
void TELL_PARENT(pid_t);
void TELL_CHILD(pid_t);
void WAIT_PARENT(void);
void WAIT_CHILD(void);

#endif //_APUE_H

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这个程序是在《UNIX环境高级编程》上的，怎么每次都是错误呢？
当我在int main(void)后加上“；”后，即int main(void);却提示PrintPID.c:3: error: expected declaration specifiers or ‘...’ before ‘{’ token

怎么回事？

root@HelloWorld:/C# gcc -v
Using built-in specs.
Target: i486-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 4.4.1-4ubuntu8' --with-bugurl=file:///usr/share/doc/gcc-4.4/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --enable-shared --enable-multiarch --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.4 --program-suffix=-4.4 --enable-nls --enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc --enable-targets=all --disable-werror --with-arch-32=i486 --with-tune=generic --enable-checking=release --build=i486-linux-gnu --host=i486-linux-gnu --target=i486-linux-gnu
Thread model: posix
gcc version 4.4.1 (Ubuntu 4.4.1-4ubuntu8)
root@HelloWorld:/C#

int buf_args(char *, int (*func)(int, char **); //这行的括号不匹配

!
谢谢CMWang同学，

顺便一题LZ怎么用root工作。。除了管理操作 root这么登陆着是有严重安全问题的