Segmentation Fault(core dumped)

0
votes

hey guys i have got this code: (im trying to read a string and put it inside the output file)

#include "structs.h"
#include <stdio.h>
#include <stdlib.h>
int main () {
  FILE* input = fopen("journal.txt", "r");
  FILE* output = fopen("output.txt", "w");
  char date[9];

  if( ferror(input) || ferror(output) ) {
    perror("Error opening input/output file\n");
  }

  fscanf(input, "%s", date);
  fgets(date, 9, input);
  fputs(date, output);
  fclose(input);
  fclose(output);
  return 0;
}

it compiles properly but at runtime it shows the error

 Segmentation fault (core dumped)

i have no idea why :( please help

2
csegmentation-fault
fopen returns NULL if the file couldn't be opened. You don't check this yet. - Zeta
If you are on *nix you can make use of gdb - Suvarna Pattayil
Why are you first fscanfing and then also fgetsing into date? - Kninnug
oh shit you were right Zeta stupid me had the wrong filename -.- thank you - Jad Sapida
Next time, use debugger before ask =) - Ivan Aksamentov - Drop

2 Answers

5
votes

You need to check whether fopen returns NULL:

#include <stdio.h>
#include <stdlib.h>
int main () {
  FILE * input;
  FILE * output;
  char date[9];

  input = fopen("journal.txt", "r");
  if(input == NULL){
    perror("Could not open input file");
    return -1;
  }

  output = fopen("output.txt", "w");
  if(output == NULL){
    perror("Could not open output file");
    fclose(input);
    return -1;
  }
/* ... snip ... */

Your input file probably doesn't exist. Calling ferror on NULL results in a segmentation fault.

0
votes
 #include <stdio.h>
 #include <stdlib.h>

   int main ()
 {
 FILE* input = fopen("journal.txt", "r");
 FILE* output = fopen("output.txt", "w");
 char date[9];

 if(input)
 {
   fscanf(input, "%s", date);
    fgets(date, 9, input);
 }
else
 {
  printf("error opening the file");
 }

if(output)
{
   fputs(date, output);
}

 else
 {
  printf("error opening the file");

 }

You were receiving the Segmentation fault as you were reading from a non-existing file 'journal.txt' and calling Ferror triggers Segmentation Fault.