c - 尝试修改a.out。使用 fwrite 写入 a.out 时出现段错误

Question

我正在尝试修改 a.out 文件。我正在寻找字符串“abc”，然后将其替换为“xyz”。然后我必须将其写入 a.out 我正在使用 fwrite 来完成此任务。但它似乎给出了段错误。 我能够将所做的更改写入新文件。但我无法写入 a.out。

在Linux上运行。

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

int  main ()
{
    static char a[100] = "abc";
    char ch, fileName[20] = "a.out";
    FILE *fp, *fpw;
    long size;
    int i;
    fp = fopen(fileName,"rb");

    if (fp == NULL)
        printf ("FILE OPEN FAILED.\n");
    else 
    {
        fseek(fp,0,SEEK_END);
        size = ftell(fp);
        printf("%d\n",size);
        //buffer = (char *) malloc(size+1);
        unsigned char buffer[size+1];
        fseek(fp,0,SEEK_SET);
        fread(buffer,size,1,fp);
        int pos_search = 0;
        int pos_text = 0;
        int len_search = 3;
        int len_text = size;
        for (pos_text = 0; pos_text < len_text - len_search;++pos_text)
        {
            if(buffer[pos_text] == a[pos_search])
            {
                ++pos_search;
                if(pos_search == len_search)
                {
                    // match
                    printf("match from %d to %d\n",pos_text-len_search,pos_text);
                    break;
                }
            }
            else
            {
               pos_text -=pos_search;
               pos_search = 0;
            }
        }

        printf("%c\n",buffer[1]);
        i = pos_text-len_search+1;
        buffer[i]   = 'x';
        buffer[i+1] = 'y';
        buffer[i+2] = 'z';
        fpw = fopen("a.out","rb+");
        fwrite(buffer,1,size-1,fpw);
        fclose(fpw);
    }

    return 0;
}

Answer 1

在打开文件的 fpw 句柄之前，您没有关闭文件的 fp 句柄