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Old 05-13-2010, 11:50 PM   #1
josip76
LQ Newbie
 
Registered: May 2010
Posts: 12

Rep: Reputation: 0
Reading in a file in C, after file read null terminator at strings end gone


Hi

In reading a file into my program using C, i used calloc to allocate and initialize the needed memory. The size of the memory allocated was the size of the file-length + 1, so that the end of the string would house the NULL-terminator. However, after i read in the file using fread and I use while(*cfile) to read the string until reaching the null char the loop becomes an infinite loop (cfile is the name of the pointer to the memory block). Its as if after using fread to read in the file contents the null terminator is gone. I attached my code below. Thanks for any help.



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

int main(int argc, char** argv)
{

FILE *fp; //file pointer
long int lfilelng; //file length

//open file
if ((fp=fopen("toberead", "rb"))==NULL) {
printf("cannot open file - 'toberead'");
exit(1);
}


if (fseek(fp, 0L, SEEK_END) !=0 ) {
printf("seek error");
exit(1);
}

lfilelng = ftell(fp);
printf("%ld\n", lfilelng);
rewind(fp);

char *cfile;

if ((cfile=calloc(lfilelng+1, sizeof(char)))==NULL) {
printf("insuficient memory to read file");
exit(1);
}

if (fread(cfile, lfilelng, 1, fp) != 1) {
printf("\nread error occured");
exit(1);
}
fclose(fp);


int i=0;
while (*cfile) { //Here is the problem
i++;
printf("\n");
printf("%d",i);
}

free(cfile);
cfile = NULL;

return 0;
}
 
Old 05-14-2010, 12:20 AM   #2
AdnanShaheen
Member
 
Registered: Aug 2009
Distribution: Suse, RedHat, CentOS, Solaris, Windows
Posts: 38

Rep: Reputation: 16
Code:
int i=0;
while (*cfile)	{	//Here is the problem
i++;
printf("\n");
printf("%d",i);
}
Until your *cfile is not null, it will continue.You are not doing any processing on "cfile" in the loop, definitely your *cfile is valid, and will be valid every time, since you are not doing any ++ or -- or cfile = null.
 
Old 05-14-2010, 12:44 AM   #3
josip76
LQ Newbie
 
Registered: May 2010
Posts: 12

Original Poster
Rep: Reputation: 0
wow that was pretty simple, im so ashamed right now lol. thanks for your help
 
  


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