text: #include <cstdio>
  #include <cstring>
  #include "files.h"
  
  #define MAXLINE 256
  
  /* ---------------------------------------------------------------------- */
  
  void replace(char *file, char *header, int n, char **lines)
  {
    FILE *fpr = fopen(file,"r");
    FILE *fpw = fopen("tmp.file","w");
  
    char line[MAXLINE];
    while (fgets(line,MAXLINE,fpr)) {
      if (strstr(line,header)) {
        fprintf(fpw,"%s",line);
        for (int i = 0; i < n; i++) {
  	fgets(line,MAXLINE,fpr);
  	fprintf(fpw,"%s",lines[i]);
        }
      } else fprintf(fpw,"%s",line);
    }
  
    fclose(fpr);
    fclose(fpw);
    rename("tmp.file",file);
  }
  
  /* ---------------------------------------------------------------------- */
  
  char **extract(char *file, char *header, int n, char **lines)
  {
    FILE *fp = fopen(file,"r");
  
    char line[MAXLINE];
    while (fgets(line,MAXLINE,fp)) {
      if (strstr(line,header)) {
        for (int i = 0; i < n; i++) {
  	fgets(line,MAXLINE,fp);
  	sprintf(lines[i],"%s",line);
        }
        break;
      }
    }
  
    fclose(fp);
  }
  