Question

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);
      }

Answer 1

pch3 is an unallocated pointer, so you’re writing data to a location that doesn’t exist. Did you mean to assign it to str?

char str[100]="";
char *pch3;
pch3 = str;
strcpy(pch3,"Ravi");