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The problem may be sscanf

  1. Oct 4, 2011 #1
    the function for read data from a txt.file.

    the data looks like:


    I use debugging tools and find the error occured in sscanf. But I can not find the specific point. please help me.

    Code (Text):

    #include <stdio.h>
    #include <stdlib.h>
    #include <math.h>
    #define BUF 10240
    #define pi 3.14159
    #define SKYFILE "H1L1V1-LUMIN_cbc_trig-970399241-1.txt"
    #define CATALOG "GWGCCatalog.txt"
    #define ResultNumber 20

    typedef struct catalogdata
    {   char pgc[20];
        char name[100];
        double ra;
        double dec;
        double absmag;
        double dist;} cdata;

    typedef struct catalogtemp
    {   char pgc[20];
        char name[100];
        char ra[30];
        char dec[30];
        char absmag[20];
        char dist[20];} catatemp;

        /* This function is for readding catalog.*/
    readevent( FILE *pFile, cdata **catalog)
        catatemp *ctemp, *ctemp1;  
        void *temp;
        int c, i=0, j, n=BUF;       /* n is the buffer. */
        if ( !(ctemp=(catatemp *)malloc(n*sizeof(catatemp))))  
            printf("memory error 1\n");                        //allocate memory.
        if ( !(temp=(char *)malloc(100)))  
            printf("memory error 1\n");                        //allocate memory for temp.

        }while(c!='\n');                                   //skip the first line.

        while (!feof(pFile))
            /*read all data as a string*/
            fscanf(pFile, "%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|%[^|]|", &(ctemp->pgc), &(ctemp->name), &(ctemp->ra), &(ctemp->dec), temp, temp, temp, temp, temp, temp, temp, temp, temp, &(ctemp->absmag), &(ctemp->dist), temp, temp, temp);
            if (i==(n-1))                              /*the number of lines is going to be longer than buffer. */
                if(!(ctemp1=realloc(ctemp, 2*n*sizeof(cdata)))) {
                    printf("memory error 2\n"); }
                n*=2;   /*double the buffer*/


        if ( !(*catalog=(cdata *)malloc(i*sizeof(cdata))))  
            printf("memory error 1\n");                        //allocate memory.

        /*convert string to data*/
            sscanf((ctemp+j)->pgc, "%s", &((*catalog+j)->pgc));
            sscanf((ctemp+j)->name, "%s", &((*catalog+j)->name));
            sscanf((ctemp+j)->ra, "%lf", &((*catalog+j)->ra));
            sscanf((ctemp+j)->dec, "%lf", &((*catalog+j)->dec));
                sscanf((ctemp+j)->absmag, "%lf", &((*catalog+j)->absmag));
                sscanf((ctemp+j)->dist, "%lf", &((*catalog+j)->dist));

    return i;      

        int i, n;
        cdata *catalog;
        FILE *pFile;
        if ( !( pFile=fopen(CATALOG, "r"))) {
            printf ("cannot open the cata_std.txt file\n");
            return 1;}
        n=readevent(pFile, &catalog);                         //catalog done.

        for(i=0; i<n; i++)
            printf("%s, %s, %e, %e, %e, %e\n", catalog[i].pgc, catalog[i].name, catalog[i].ra, catalog[i].dec, catalog[i].absmag, catalog[i].dist);


  2. jcsd
  3. Oct 4, 2011 #2


    User Avatar
    Homework Helper

    You only allocate one instance of catalog in main, but you treat it as an array in readevent() when you reference ( ... catalog + j ...). It might also help to add temporary code to print out the structure for each loop in readevent().
  4. Oct 4, 2011 #3
    I find something
    &(ctemp->pgc), &(ctemp->name), should be (ctemp+i)->pgc
    but still out of order
  5. Oct 5, 2011 #4


    Staff: Mentor

    When you are using the debugger and see a problem with sscanf, which line is causing the problem, and what is the error that is generated?
  6. Oct 5, 2011 #5
    i==14168 causing the problem
    memory error...
  7. Oct 5, 2011 #6
    in fact, the error occur in fscanf()
  8. Oct 5, 2011 #7


    Staff: Mentor

    Here's my guess. The heap memory that temp points to consists of 100 bytes. One of the file reads (using fscanf) pulls in a string that's too big to fit in 100 bytes, which causes the problem you're seeing.

    Instead of using fscanf to input to six variables you care about, and a slew of "don't care" variables, it might be better to have a loop. Each iteration of the loop could read one line of data from the file and store it in a string, and then parse the string.
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