C中的字符串复制导致分段错误(String copy in C causing segmentation fault)

我试图复制一个字符串到另一个字符指针变量使用strcpy函数。但我总是得到分段fault.Here是我的代码。

/* strcat example */ #include <stdio.h> #include <string.h> int main() { char str[100]=""; char *pch3; strcpy(pch3,"Ravi"); //strcat(str,pch3); //Segmnetation fault. puts(pch3); return 0; }

如果我在这一个做同样的事情，我仍然是分段错误。

else { misc_rec_cnt++; fp1=fopen("breast-cancer-wisconsin-miscellaneous.data","a"); fprintf(fp1,"%s",line2); fclose(fp1); fp2=fopen("missingSCNs.data","a"); pch2=strtok(line2,","); fprintf(fp2,"%s\n",pch2); fclose(fp2); //pch3=(char *)malloc(sizeof(char)*strlen(line3)); pch3 = strtok(line3,","); while(pch3!=NULL) { if(strcmp(pch3,"?") == 0) { strcat(str1,"0"); strcat(str1,","); } else { //strcat(str1,pch3); strcat(str1,","); } pch3 = strtok(NULL,","); } strlen1=strlen(str1); memcpy(str2,str1,strlen1-1); fp3=fopen("breast-cancer-wisconsin-miscellaneous-cleansed.data","a"); fprintf(fp3,"%s\n",str2); fclose(fp3); }

I am trying to copy a string into another char pointer variable using strcpy function.But I always get segmentation fault.Here is my code.

/* strcat example */ #include <stdio.h> #include <string.h> int main() { char str[100]=""; char *pch3; strcpy(pch3,"Ravi"); //strcat(str,pch3); //Segmnetation fault. puts(pch3); return 0; }

If I do the same thing in this one I still get segmentation fault.

else { misc_rec_cnt++; fp1=fopen("breast-cancer-wisconsin-miscellaneous.data","a"); fprintf(fp1,"%s",line2); fclose(fp1); fp2=fopen("missingSCNs.data","a"); pch2=strtok(line2,","); fprintf(fp2,"%s\n",pch2); fclose(fp2); //pch3=(char *)malloc(sizeof(char)*strlen(line3)); pch3 = strtok(line3,","); while(pch3!=NULL) { if(strcmp(pch3,"?") == 0) { strcat(str1,"0"); strcat(str1,","); } else { //strcat(str1,pch3); strcat(str1,","); } pch3 = strtok(NULL,","); } strlen1=strlen(str1); memcpy(str2,str1,strlen1-1); fp3=fopen("breast-cancer-wisconsin-miscellaneous-cleansed.data","a"); fprintf(fp3,"%s\n",str2); fclose(fp3); }