got a seg fault

This is a discussion on got a seg fault within the C Programming forums, part of the General Programming Boards category; i have a seg fault please help. It happens when i go to open a file. if the file has ...

  1. #1
    ck1
    ck1 is offline
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    Mar 2005
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    got a seg fault

    i have a seg fault please help. It happens when i go to open a file. if the file has data i get a seg fault. if the file is empty its all ok and i get the proper message.
    Code:
    void open_batch()
    {
       char f[100];
       char c;
       int a = 0, b = 0;
       int eof = 0;
       int d, e, g, h, i, j, k;
       printf("Please enter the file you wish to run: ");
       scanf("%s", f);
       if(file == NULL)
       {
          printf("File is empty!\n\n");
          exit(1);
       }
       while(eof == 0)
       {
          c = fgetc(file);
          if((c == 70) || (c == 102) || (c == 85) || (c == 117))
          {
             for(d = 0; d <= 3; d++)
             {
                u_type[d] = c;
                c = fgetc(file);
                printf("%c", u_type[d]);
             }
    ...
    ...

  2. #2
    Gawking at stupidity
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    Jul 2004
    Location
    Oregon, USA
    Posts
    3,159
    You don't actually call fopen() anywhere...
    If you understand what you're doing, you're not learning anything.

  3. #3
    ---
    Join Date
    May 2004
    Posts
    1,379
    Code:
    printf("Please enter the file you wish to run: ");
       scanf("%s", f);
       if(file == NULL)
       {
    You can't just expect to input a string and be able to call it a file.

    you need to open it...
    Code:
    FILE *fp;
    char c;
    fp=fopen("file.txt","r");
    c = getc(fp);
    Oh and make sure you check the return value of fopen() and also dont use scanf to input strings, use fgets()

  4. #4
    Lost In Rain
    Join Date
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    If you want to take the file name as ainput from user....this will do

    Code:
    #include <stdio.h>
    #include <conio.h>
    
    void main(){
    
    	FILE *fp;
    	char name[30];
    	clrscr();
    	scanf("%s",&name);
    	if ((fp=fopen(name,"rt"))==NULL){
    		printf("No such file");
    	}
    	else
    		printf("File exists");
    	.......................
    You will input the file name by full path ie. c:\text.txt

    Do notice that while writing directly in a program we use double slash(\\) but while typing the input we use one slas(\)

    to read use this

    Code:
       while(!feof(fp))
       {
             ch=fgetc(fp);
              . . . . }
    Dont forget to close the file everytime you work with file in program

    Code:
    fclose(fp);

  5. #5
    and the hat of wrongness Salem's Avatar
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    > void main(){
    > while(!feof(fp))
    Why both of these are bad are in the FAQ - read them
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

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