C：初始元素不是常數

Question

我學習Cfork()，我有這些錯誤：

app.c:13:1: warning: data definition has no type or storage class [enabled by default] 
app.c:13:1: error: initializer element is not constant 
app.c:15:1: error: expected identifier or ‘(’ before ‘if’ 
app.c:20:1: error: expected identifier or ‘(’ before ‘else’ 
app.c:26:1: error: expected identifier or ‘(’ before ‘else’ 

這裏是源代碼：

#include <sys/types.h> 
#include <sys/stat.h> 
#include <fcntl.h> 
#include <stdio.h> 
#include <stdlib.h> 

int f; 
pid_t pid; 

char msga[] = "abcd"; 
char msgb[] = "wxyz"; 

f = open("toto", O_WRONLY|O_TRUNC|O_CREAT,S_IRUSR|S_IWUSR); 

if ((pid = fork()) == -1) { 
    perror("fork"); 
    exit(EXIT_FAILURE); 
} 

else if (pid == 0) { 
    wait(NULL); 
    write(f, &msga, strlen(msga)); 
    close(f); 
} 

else { 
    wait(NULL); 
    write(f, &msgb, strlen(msgb)); 
    close(f); 
} 

Answer 1

你需要用所有那個（在#include之後）函數裏面！

int main(void) 
{ 
... 
} 

你可能要添加return 0;末那裏。

在快速測試在這裏，我還需要補充：

#include <unistd.h> 
#include <string.h> 

要獲得fork(2)和strlen(3)的聲明，resepectively。