segmentaion fault with File Input/Output

Hi,

I have a text file with the following formating:
+
12
12

I am making a program that reads the file and takes the file name that the user entered and conctenate the .out to the new file and output the results for example 12+12=24 so 24 should go in the new file. I am getting the segmentaion fault when I try to scan the name of the file from the user.


My code:

Code:

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

int main(int argc,char**argv){
char c[10];  /* declare a char array */
  FILE *file;  /* declare a FILE pointer  */
  char *filename;
  printf("Please enter the file name: ");
  scanf("%s",&filename);
  char *cc;
  char *dd=".txt";
  cc=strcat(filename, dd);  // the file name
   file = fopen(cc, "r");
  /* open a text file for reading */

  if(file==NULL) {
    printf("Error: can't open file.\n");
    return 1;
  }
  else {
    printf("File opened successfully. Contents:\n\n");

    while(fgets(c, 10, file)!=NULL) {
      /* keep looping until NULL pointer... */
      printf("String: %s", c);
      /* print the file one line at a time  */
    }

    printf("\n\nNow closing file...\n");
    fclose(file);
    return 0;
  }

}

Use an array instead of a pointer. filename is just a pointer, which points to nothing specific. That is to say, it's uninitialized, so it just points to some arbitrary point in memory, which likely isn't yours to play with. Use an array, or allocate some memory for your file name.


Quzah.

thanks that worked I am now trying to add the 12 and the 12: It only reads the +11: its only reading the first characters.

Code:

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

int main(int argc,char**argv){
char c[10];  /* declare a char array */
  FILE *file;  /* declare a FILE pointer  */
  char filename[20];
  printf("Please enter the file name: ");
  scanf("%s",&filename);
  char *cc;
  char *dd=".txt";
  cc=strcat(filename, dd);  // the file name
   file = fopen(cc, "r");
  /* open a text file for reading */

  if(file==NULL) {
    printf("Error: can't open file.\n");
    return 1;
  }
  else {
    printf("File opened successfully. Contents:\n\n");
    int one;
    int two;
    int three;

    while(fgets(c, 10, file)!=NULL) {
      one=c[0];
      two=c[1];
      three=c[2];
      printf("%s", &one);

    }

    printf("\n\nNow closing file...\n");
    fclose(file);
    return 0;
  }

}

Code:

$ gcc -W -Wall -ansi -pedantic -O2 foo.c
foo.c: In function `main':
foo.c:10: warning: char format, different type arg (arg 2)
foo.c:11: warning: ISO C90 forbids mixed declarations and code
foo.c:23: warning: ISO C90 forbids mixed declarations and code
foo.c:31: warning: char format, different type arg (arg 2)
foo.c: At top level:
foo.c:5: warning: unused parameter 'argc'
foo.c:5: warning: unused parameter 'argv'

Fix your printf and scanf calls for starters.
Also // is not a comment in standard C
It is a comment as an extension to C89, or in C99 or C++

> cc=strcat(filename, dd); // the file name
> file = fopen(cc, "r");
cc is useless, you may as well just do
strcat(filename, dd);
file = fopen(filename, "r");

1) You don't have a read to get the operator.
2) In this code:

Code:

    while(fgets(c, 10, file)!=NULL) {
      one=c[0];
      two=c[1];
      three=c[2];
      printf("%s", &one);

you can't expect to move the characters into ints and expect a number out of it. After you read a number line, use atoi() to convert the buffer into a number you can do math on:

Code:

fgets(c, 10, file);
one=atoi(c);

Or use scanf() to get ints, like they were created to do.

Or use scanf() to get ints, like it was originally created to do.

thanks guys I got it to work..