例程四、c讀寫文件與文件參數管理

直接上代碼，代碼簡單易懂。

#include<stdio.h>
#define PARAM_CONFIG "/home/lkg/test/config"
typedef struct{
    unsigned short int id;
    int offset;
}param_offset;
typedef struct {
    char c;
    int h;
    unsigned short n;
    char s[4];
}st;
  ram_offset id_offset[3] =  {
▽   {1,0},
    {2,8},                    
    {3,108},                  
};                                                                                                                                                                              
int param_write_cfg(st* buffer, unsigned short int param_id){
    int ret, i, offset;
    FILE *fp;
    i = 0;
    while(id_offset && id_offset[i].id){
        if(param_id == id_offset[i].id){
            offset = id_offset[i].offset;
            break;
        }
        i++;
    }
    printf("id = %d, offset = %d\n", param_id, offset);        
    if((fp = fopen(PARAM_CONFIG, "rb+")) == NULL) {
        if((fp = fopen(PARAM_CONFIG, "wb+")) == NULL) {
            printf("Can't open %s, program will to exit.\n", PARAM_CONFIG);
            return -1;
        }
    }
    fseek(fp, offset, SEEK_SET);
    fwrite(buffer, sizeof(*buffer), 1, fp);
    printf("st c = %d, h = %d n =%u s = %s \n",buffer->c, buffer->h,buffer->n,buffer->s); 
    fclose(fp);
    return 0;
}
int param_read_cfg(st* buffer, unsigned short int param_id){
    int ret, i, offset;
    FILE *fp;
 ~/test/param.c[+1]                                                                                                                                      [c] unix utf-8 1:17/81 
"param.c" 81L, 2187C written
lkg@ubuntu:~/test$ gcc param.c 
lkg@ubuntu:~/test$ ./a.out 
id = 2, offset = 8
st c = 5, h = 7 n =0 s = didi 
id = 3, offset = 108
st c = 6, h = 2 n =0 s = dada 
id = 2, offset = 8
st c = 5, h = 7 n =0 s = didi 
id = 3, offset = 108
st c = 6, h = 2 n =0 s = dada 
lkg@ubuntu:~/test$ vi param.c 
 *
 *讀取文件指定id位置存儲的結構體內容
 *
 */
int param_read_cfg(st* buffer, unsigned short int param_id){
    int ret, i, offset;
    FILE *fp;
    param_offset id_offset[3] =  {
        {1,0},
        {2,8},                             
        {3,108},                           
    };  
    i = 0;
    while(id_offset && id_offset[i].id){
        if(param_id == id_offset[i].id){
            offset = id_offset[i].offset;
            break;
        }   
        i++;
    }   
    printf("id = %d, offset = %d\n", param_id, offset);            
    if((fp = fopen(PARAM_CONFIG, "rb+")) == NULL) {
        printf("Can't open %s, program will to exit.", PARAM_CONFIG);
        return -1; 
    }   
    fseek(fp, offset, SEEK_SET);
    fread(buffer, sizeof(*buffer), 1, fp);
    printf("st c = %d, h = %d n =%u s = %s \n",buffer->c, buffer->h,buffer->n,buffer->s);
    fclose(fp);
    return 0;  
 
}
int main(){
//    char version[] = "1.0.5";
    st t;
    st tt = {5,7,0,"didi"};
    st tt1 = {6,2,0,"dada"};
//    param_write_cfg(version,1);
    param_write_cfg(&tt,2);
    param_write_cfg(&tt1,3);
    param_read_cfg(&t,2);
    param_read_cfg(&t,3);
    return 0;
}