不知道为什么文件打不开

问题描述

这是我的代码

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

#define TRUE    1
#define FALSE   0

typedef struct {    
    int M,N;    
    int min,max;    
    int width;    
    int height;    
    unsigned char **pixels;    
}PPMIMG;
    
int fnReadPPM(char* fileNm,PPMIMG* img);

int main(int argc,char ** argv)
{    
    PPMIMG img;        

    if(fnReadPPM(argv[1],&img) != FALSE)
    {    
        return TRUE;    
    }

    return  0;
}

int fnReadPPM(char* fileNm,PPMIMG* img)
{    
    FILE* fp;    
    fp = fopen("/users/ashton/Downloads/test.txt","rb");
    
    if(fileNm == NULL){    
        fprintf(stderr,"Unable to File ! : %s\n",fileNm);    
        return FALSE;    
    }
    
    fclose(fp);    
    return TRUE;
}

int fnWritePPM(char* fileNm,PPMIMG* img)
{    
    FILE *fp =fopen(fileNm,"w");    
    if(fp == NULL)
    {    
        fprintf(stderr,"Failed to create the file.");    
        return FALSE;    
    }        
    return TRUE;
}

这是错误代码：

Unable to File ! : (null)
Program ended with exit code: 0 

解决方法

您错误地测试了 fopen 返回值：

fp = fopen("/users/ashton/Downloads/test.txt","rb");
if (fp == NULL) {    //<===== Was WRONG,you used fileNm instead of fp
    perror("Unable to File");
    return FALSE;
}

,

问题很可能在这里：

int fnReadPPM(char* fileNm,PPMIMG* img)
{
    FILE* fp;
    fp = fopen("/users/ashton/Downloads/test.txt","rb"); // you assign fp
    
    if (fileNm == NULL){                                // and here you check for fileNm 
        fprintf(stderr,"Unable to File ! : %s\n",fileNm);
        return FALSE;
    }    
    ...

你想要这个：

int fnReadPPM(char* fileNm,"rb");
    
    if (fp == NULL) {
        fprintf(stderr,"Unable to open file %s.\n",fileNm);
        return FALSE;
    }    
    ...

但是在 fnWritePPM 函数中，您做得对。