wavenumber       wavelength       powerspec
    zzleifjl        qwefaseklfj        asjfieasef //second row was cracked
    0.00000000002356234 0.00000013431  0.12523125123
    0.0000000000412512  0.00000054888  0.58382423
    etc..

/*openfiles according to reprogramed filelist*/
for(i =2; i<file_count; i++) {
       strcat(filelist[i],".txt");
       if((fp = fopen( filelist[i], "r")) == NULL)
       {
               perror("error to openfiles");
               exit(1);
       }

       /*declare the variables*/
       char data[3][513];
       //char wavenumber[513], wavelength[513], powerspec[513];
       int COL, ROW, MAX_wavenumber, MAX_wavelength, MAX_powerspec;
       int HEIGHT,WIDTH;
       HEIGHT = 513;
       WIDTH = 3;


       //input data to new array
       for(COL = 0; COL < HEIGHT; COL++) {
               for (ROW = 0; ROW < WIDTH; ROW++) {
                       fscanf(fp, "%s", &data[ROW][COL]);
               }
       }

       //start of comparison of data

       for(COL = 2; COL < HEIGHT - 1; COL++) {  //number starts from the 3rd column
               while(ROW == 1) {
                       if( atof(&data[ROW][COL]) < atof(&data[ROW][COL+1]) ) {
                               MAX_wavenumber = atof(&data[ROW][COL+1]);
                       }
                       while(ROW == 2) {
                               if( atof(&data[ROW][COL]) < atof(&data[ROW][COL+1]) ) {
                                       MAX_wavelength = atof(&data[ROW][COL+1]);
                               }
                       }
                       while(ROW == 3)
                               if( atof(&data[ROW][COL]) < atof(&data[ROW][COL+1]) ) {
                                       MAX_powerspec = atof(&data[ROW][COL+1]);
                          }
               }
       }

       printf("MAX_wavenumber : %d",MAX_wavenumber);
       printf("MAX_wavelength : %d",MAX_wavelength);
       printf("MAX_powerspec : %d",MAX_powerspec);

  fclose(fp);
}

#include <stdio.h>
    #include <stdlib.h>
    #include <math.h>
    #include <dirent.h>
    #include <sys/types.h>
    #include <sys/stat.h>
    #include <unistd.h>
    #include <string.h>

char *remove_ext (char* mystr, char dot, char sep);

int main()
{
        char fname1[256],fname2[256];
        char folderpath[256];
        int mod;
        int re_mainder;
        char *tem;
        char filenameNoExtension;

        char **filelist;
        int i,j,l;
        char ***ls = &filelist;

        int file_count = 0;

        char *s;

        DIR* dp = NULL;
        struct dirent* entry = NULL;

        FILE* fp = NULL;


/*open folder*/
        printf("enter the folder path : ");
        scanf("%s",folderpath);

/*  Err message of opening directory */
        if((dp = opendir(folderpath)) ==NULL) {
                fprintf(stderr,"unidentified folder : %s",folderpath);
                return 0;
        }

        *ls = NULL;

/*file count*/
        while ((entry = readdir(dp)) != NULL) {
                if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
                        continue;
                ++file_count;
        }

/* rewind the directory and need to reallocate memory for reading 18250 files */
        rewinddir(dp);
        *ls = calloc(file_count, sizeof(char*));

/*make the array of filelist*/
        file_count = 0;
        entry = readdir(dp);
        while(NULL != entry) {
                (*ls)[file_count++] = strdup(entry->d_name);
                entry = readdir(dp);
        }

/*remove the extension */
        for(i = 0; i < file_count; i++) {
                filelist[i] = remove_ext(filelist[i], '.', '/');
        }
        closedir(dp);
//loop starts at 2 for get rid of space & .
        for(i = 2; i< file_count; i++) {
                printf("%sn",filelist[i]);
        }



/*select the mod & remainder*/
        printf("select the mod number : ");
        scanf("%d", &mod);
        printf("select the remainder : ");
        scanf("%d",&re_mainder);


/*sort files by the remainder*/
        for(i = 2; i<file_count; i++) {
                if( atoi( filelist[i] )%mod == re_mainder) { /*use atoi function for changing string to int*/
                        filelist[i] = filelist[i];
                }
                else
                        filelist[i] = "delete";
        }

//delete the  "delete" in array
        l = file_count;
        for(i = 0; i<l; i++) {
                if (strcmp(filelist[i], "delete") == 0 ) {
                        for(j = i; j < l; j++)
                                filelist[j]=filelist[j+1];
                        i--; //check again from same index i
                        l--; //Decreasing the length of the array
                }
        }
        /* resize the modified file_count */
        file_count = sizeof(filelist)/sizeof(filelist[0]);
        for(i =2; i<file_count; i++) {
                printf("%sn",filelist[i]);
        }


        /**********           **HERE"S MY QUESTION**              **********/
        /**********openfiles according to reprogramed filelist**********/


        for(i =2; i<file_count; i++) {

                strcat(filelist[i],".txt");
                if((fp = fopen( filelist[i], "r")) == NULL)
                {
                        perror("error to openfiles");
                        exit(1);
                }

                /*declare the variables*/
                char data[3][513];
                //char wavenumber[513], wavelength[513], powerspec[513];
                int COL, ROW, MAX_wavenumber, MAX_wavelength, MAX_powerspec;
                int HEIGHT,WIDTH;
                HEIGHT = 513;
                WIDTH = 3;


                //input data to new array
                for(COL = 0; COL < HEIGHT; COL++) {
                        for (ROW = 0; ROW < WIDTH; ROW++) {
                                fscanf(fp, "%s", &data[ROW][COL]);
                        }
                }

                //start of comparison of data

                for(COL = 2; COL < HEIGHT - 1; COL++) {  //number starts from the 3rd column
                        while(ROW == 1) {
                                if( atof(&data[ROW][COL]) < atof(&data[ROW][COL+1]) ) {
                                        MAX_wavenumber = atof(&data[ROW][COL+1]);
                                }
                                while(ROW == 2) {
                                        if( atof(&data[ROW][COL]) < atof(&data[ROW][COL+1]) ) {
                                                MAX_wavelength = atof(&data[ROW][COL+1]);
                                        }
                                }
                                while(ROW == 3)
                                        if( atof(&data[ROW][COL]) < atof(&data[ROW][COL+1]) ) {
                                                MAX_powerspec = atof(&data[ROW][COL+1]);
                                        }
                        }
                }

                printf("MAX_wavenumber : %d",MAX_wavenumber);
                printf("MAX_wavelength : %d",MAX_wavelength);
                printf("MAX_powerspec : %d",MAX_powerspec);


                fclose(fp);
        }
}


//this is just for removing the extension of files
char *remove_ext (char* mystr, char dot, char sep) {
        char *retstr, *lastdot, *lastsep;

        // Error checks and allocate string.

        if (mystr == NULL)
                return NULL;
        if ((retstr = malloc (strlen (mystr) + 1)) == NULL)
                return NULL;

        // Make a copy and find the relevant characters.

        strcpy (retstr, mystr);
        lastdot = strrchr (retstr, dot);
        lastsep = (sep == 0) ? NULL : strrchr (retstr, sep);

        // If it has an extension separator.

        if (lastdot != NULL) {
                // and it's before the extenstion separator.

                if (lastsep != NULL) {
                        if (lastsep < lastdot) {
                                // then remove it.

                                *lastdot = '';
                        }
                } else {
                        // Has extension separator with no path separator.

                        *lastdot = '';
                }
        }
        // Return the modified string.

        return retstr;
}