whats wrong wid dis code!!

**smooth** · 09-13-2008

Hi all,

Please help me wid the code below..it gives a segmentation fault on execution..
compilation is clean..m running it on gcc (linux)..

its a simple program to copy text from a file and store in a local variable
cannot figure out wat 2 do

Code:

#include<stdio.h>
#include<string.h>
#define IN 1
#define OUT 0

main()
{
FILE *fp;
char *ch = "";
char *str = "";
int c, state;
state = OUT;

printf("HI all");
fp = fopen("output.txt", "r");
if(fp == NULL)
{
    puts("\nCannot open source");
    return(0);
}

while ((c = fgetc(fp)) != EOF)
{
    if (c == ' ' || c == '\n' || c == '\t')
    {
        state = OUT;
    }
    else
    {
        state = IN;
        *ch = (char) c;
        strcat(str,ch);
    }
}
fclose(fp);
printf("%s",str);
}

**vart** · 09-13-2008

main()
should be
int main(void) - read FAQ

char *ch = ""; - points to some write protected memory
char *str = ""; - same here - you cannot write to this destination

strcat(str,ch); - you need some buffer before writing, you have none

to add 1 char to buffer - you do not need the strcat, simple assignment will do...

**anon** · 09-13-2008

Code:

char *ch = "";
char *str = "";
...
        *ch = (char) c;
        strcat(str,ch);

You are trying to write something to non-modifiable location (string literals cannot be overwritten) where you don't have any room anyway.

Try to get some modifiable buffer with sufficient size:

Code:

char str[1000] = {0};

There should also be better ways to append one character at a time to a buffer.

**smooth** · 09-13-2008

thanks 4 d help BUT

I changed it to....using a buffer and then strcat..removed d above str="" and ch=""...
it still gives d seg fault

Code:

        char ch[200];
        ch[i] = (char) c;
        strcat(str,ch);
        i++;

and any way2 append a buffer or even one char at atime 2 a string..m out f ideas

**vart** · 09-13-2008

Code:

char str[200]
size_t len = 0;
while ((c = fgetc(fp)) != EOF)
{
    if (c == ' ' || c == '\n' || c == '\t')
    {
        state = OUT;
    }
    else
    {
        state = IN;
        str[len] = c;
        len++;
        str[len] = 0;
        if(len >= sizeof (str) - 1)
           break;
    }
}

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