problem:retrieve from struct

kelly80 · #1 28-Apr-2004, 01:59

The program below encounter a problem, which when i print out a set of data retrieve from struct, it give me totally different value..the first fprintf() return me the value that i want(which are *2609_AUS74....), but when i put the fprintf() inside another for loop, it just return me [1] [1].....i have attached the input file in the attachmant...

CPP / C++ / C Code:

#include <stdio.h>
#include <conio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <assert.h>

typedef struct {
	char *seq_names;
	char *context[893];
}myStruct;

void main()
{
	FILE *infile;
	FILE *outFile;

	int sampleNo, nukloideNo, win=5, con=3;
	char cont[10];
	char filename[30];
	char sequence[12];
	char *m;
	myStruct seq[16];


	do
	{
   		printf("Please enter the input file name:");
		scanf("%s",filename);

	}while((infile=fopen(filename,"r"))==NULL);

	outFile=fopen("outfile","w");
	if(outFile==NULL)
	{
		 printf("Unable to open output file.");
		 exit(0);
	}

	fscanf(infile,"%d %d %d %d", &sampleNo, &nukloideNo, &win, &con);


	int j;
	int i=-1;


	while(fgets(sequence, 12, infile)!=NULL) { 

		if(strstr(sequence,"*")!=NULL)
			{
			i++;
			seq[i].seq_names=sequence;

			fprintf(outFile,"%s\n",seq[i].seq_names);//first fprintf
			j=0;
		
			}

  		else if(strstr(sequence,"#")!=NULL){

			seq[i].context[j]=sequence;
		             j++;}
	
    }

	for(int k=0;k<=i;k++)
		fprintf(outFile,"%s",seq[k].seq_names );//2nd fprintf


	fclose(outFile);
	printf("\nPress any key to Terminate.");
             getch();

   
	return;
}

could anyone tell me why??and how to resolve this problem??

Any help is appreciated!!

dsmith · #2 28-Apr-2004, 09:01

Hi kelly.

The problem you are having is that you are simply assigning your char* to a static string array (sequence). Therefore all of your seq_names are simply pointing to the exact same static memory location as defined by sequence. And the contents of sequence are getting overwritten by each call to fgets. Since "[1]" is the last entry in your file, this is the apparent contents of all of your seq_names.

To fix this, you need to allocate memory for you seq_names and then use the strcpy command to copy the static string contents to the new memory location.

Try something like this:

CPP / C++ / C Code:

  
if(strstr(sequence,"*")!=NULL)
      {
      i++;
      /*Start of Change*/
      seq[i].seq_names = (char*) malloc(strlen(sequence)+1);
      strcpy(seq[i].seq_names,sequence);
      /*End of change*/

      fprintf(outFile,"%s\n",seq[i].seq_names);//first fprintf
      j=0;

Hope this helps,
d

kelly80 · #3 28-Apr-2004, 21:33

thanks dsmith,

yup, its really solve my problem

..em..but another problem comes,as u taught, i also change the part after

CPP / C++ / C Code:

      char *context[893];

      else if(strstr(sequence,"#")!=NULL){

      seq[i].context[j]=sequence;
                 j++;}
  
    }

to

CPP / C++ / C Code:

    char *context[10];   

    else if(strstr(sequence,"#")!=NULL){

    seq[i].context[j]=(char*) malloc(strlen(sequence)+1);
    strcpy(seq[i].context[j],sequence);
	
    fprintf(outFile,"%d",j);
    fprintf(outFile,"%s\n",seq[i].context[j]);   //first fprintf
    j++;}
	
    }

   for(int k=0;k<=i;k++)
           for(int l=0;l<j;l++){
	fprintf(outFile,"%s",seq[k].seq_names );
	fprintf(outFile,"%d",l);
	fprintf(outFile,"%s\n",seq[i].context[j]);   //2nd fprintf
}

but the program also cannot return me the correct answer in the 2nd fprintf..(it also return only [1][1]..)

can u tell me what should i do??thanks again..

dsmith · #4 28-Apr-2004, 22:34

Hey kelly. I am not sure that I understand your subscripting. I may be wrong, but shouldn't this line:

CPP / C++ / C Code:

fprintf(outFile,"%s\n",seq[i].context[j]);

Be more like:

CPP / C++ / C Code:

fprintf(outFile,"%s\n",seq[k].context[l]);

Otherwise you are just printing the last element each time.

HTH,
d

kelly80 · #5 28-Apr-2004, 23:05

thanks dsmith,
actually i also just realise that..see how careless i am..

kelly80 · #6 29-Apr-2004, 03:24

how to free the memory for these:

CPP / C++ / C Code:

seq[i].seq_names = (char*) malloc(strlen(sequence)+1);
seq[i].context[j]=(char*) malloc(strlen(sequence)+1);

thanks..

dsmith · #7 29-Apr-2004, 08:49

Quote:

Originally Posted by kelly80

how to free the memory for these:

CPP / C++ / C Code:

seq[i].seq_names = (char*) malloc(strlen(sequence)+1);
seq[i].context[j]=(char*) malloc(strlen(sequence)+1);

thanks..

The opposite of malloc is the free command. So you would use:

CPP / C++ / C Code:

free(seq[i].seq_names);

Cheers,
d

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