CS50恢复问题：无法打开文件

如何解决CS50恢复问题：无法打开文件

我正在研究pset4 cs50的恢复分配，我想我已经完成了代码。但是，当我运行它时，它说：无法打开文件。如果我尝试双击文件'card.raw'，则会弹出一个窗口，提示：“无法打开card.raw：文件格式不受支持”。请帮助我找出我的问题。这是我的代码：

#include <stdio.h>
#include <stdlib.h>

int main(int argc,char *argv[])
{
      FILE * pFile = NULL;
     unsigned char *buffer = malloc(512);
      char* filename = NULL;
      int filenumber = 0;
    //If user didn't print 2 items
    if(argc != 2)
    {
        printf("Usage: ./recover image\n");
        return 1;
    }
    //THE PROBLEM IS HERE!!!
    //if it can't open the file: error message
      if (!pFile)
    {
        fprintf(stderr,"File cannot be opened\n");
        return 2;
    }
    //Open the file
pFile = fopen(argv[1],"r");
int j=0; 
// checking the card by 512b chunks 

//loop
while (pFile)
{
  int i =0;
  i++;

//k=fread (buffer,512,i,*file);
int k = fread(buffer,pFile);
//if buffer [0]== 0xff // checking if it's the header. If yes - creating a new jpeg;
if (buffer[0] == 0xff && buffer[1] == 0xd8 && buffer[2] == 0xff && (buffer[3] & 0xf0) == 0xe0)
{
// if it's not the first file,we should close the last one
if (filename != NULL)
{
    fclose(pFile);
}
//sprintf
sprintf(filename,"%03i.jpg",2);
//FILE = fopen (W) 
pFile = fopen(filename,"w");
// fwrite (buffer,j,*file1)
fwrite (buffer,pFile);
//j=j+1
j = j + 1;
}
// if k<512 - end of the loop
if (k < 512)
{
    return 0;
}
}
free(buffer);
}

请帮助我理解。谢谢。

解决方法

您正在检查打开文件之前尝试打开文件是否失败：

    if (!pFile)
    {
        fprintf(stderr,"File cannot be opened\n");
        return 2;
    }
    //Open the file
    pFile = fopen(argv[1],"r");

只需在测试之前将fopen调用移到上面，看看它是否成功：

    //Open the file
    pFile = fopen(argv[1],"r");
    if (!pFile)
    {
        fprintf(stderr,"File cannot be opened\n");
        return 2;
    }