Thread: What's wrong with my code here???

Hello, everybody. Need help with this program. It's meant to take a pattern 1 and replace the first occurance in a string with pattern 2. The patterns are case sensitive. I keep getting a segmentation fault.

Here's an example of what the code should do:

Text before code:

Chris is great!
Is
is

Text after code with i as pattern 1 and x as pattern 2.

Chrxs is great!
Is
xs

Here's my code:

Code:

#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>

int main(int argc, char *argv[])
{
 char str[5];        //Char to hold .out
 char * line;        //Char to hold line read in.
 char * pch;         //Char to hold first occurance of pattern
 char * string;      //Char to hold the entire string.
 char * string2;     //Makes a second array to hold the modified string.
 char * replace1;    //Char to hold string of pattern to replace.
 char * replace2;    //Char to hold string of pattern to replace with.
 FILE * inFILE;      //Name of file to read in.
 char * outFILE;     //Name of outfile.
 int in, out;        //Int to hold the return values of in, out, and nread.

 if (argc != 4)
 {
  fprintf(stderr,"Not enough arguments.\n"); //Prints out error message if there is not 
                                             //enough arguments.
  exit(1); //Exits the program and returns failure.
 }
 strcpy (str, ".out"); //Copies .out to str.
 replace1 = argv[2]; //Gets the pattern to be replaced from the arguments.
 replace2 = argv[3]; //Gets the pattern that will replace pattern one from the arguments.
 string = (char*) malloc (101); //Allocates memory for string.
 inFILE = fopen(argv[1],"r"); //Opens the file.
 outFILE = argv[1]; //Gets the name of the file.
 strncat (outFILE,str,5); //Adds .out to that end of the file.
 out = open(outFILE, O_RDWR|O_CREAT, S_IRUSR|S_IRGRP|S_IROTH|S_IWUSR); //Uses system calls
 //to open the outfile and create permissions for the file.

 if (out == -1)
 {
  fprintf(stderr, "Error with system calls.\n"); //Prints error message if there is an error
                                                 //opening the outfile.
  exit(1); //Exits the program and returns failure.
 }
 if (inFILE == NULL)
 {
  fprintf(stderr, "Error opening file.\n"); //Prints error message if there is an error
                                            //opening the infile.
  exit(1); //Exits the program and returns failure.
 }
 if (!feof(inFILE))
 {
  line = fgets(string, 101, inFILE); //Gets a string from the array.
  pch = strstr (line,replace1); //Finds the first occurance of replace1.
  int index; //Declares an int variable named index.
  string2 = (char *) malloc (101); //Allocates memory for string2.
  index = strlen(string2); //Makes index equal to the length of string2
  if (pch == NULL)
   strcpy (string2, string); //Copies string if pch is null.
  else
   memcpy (string2, line, (strlen(string) - strlen(pch))); //Copies the string up to the
                                                           //first occurance of replace1.
   string2[index] = '\0'; //Adds null terminating value to the end of string2.
   strncat (string2, replace2, strlen(replace2)); //Adds replace2 to the modified string.
   strncat (string2, pch + strlen(replace1), (strlen(pch) - strlen(replace1))); //Adds the
   //rest of the string to the modified string.

   write (out, string2, strlen(string2)); //Writes the string to file.
 }
 else
  fprintf(stderr, "Error detected in file.\n"); //Prints error message if there is an error
                                                //with the file.
  exit(1); //Exits the program and returns failure.
 if (out == -1)
 {
  fprintf(stderr, "Error with system calls.\n"); //Prints error message if there is an error
                                                 //closeing the file.
  exit(1); //Exits the program and returns failure.
 }
 close(out); //Closes the output file.
 fclose (inFILE); //Closes the input file.
 free (string2); //Frees the memory used to create string2.
 free (string); //Frees the memory used to create string.
 exit(0); //Exits program and returns success.
}

Any help given will be greated appreciated.

Thanks!!!

Signed,

Chris Beech