COMP1721 - Higher Computing 1B

1. #include <stdio.h>
   
   int
   main(int argc, char *argv[]) {
       FILE *f;
       int i;
       
       f = fopen("numbers", "w");
       if (f == NULL) {
           fprintf(stderr, "Can not openm file numbers for writing\n");
           return 1;
       }
       for (i = 1; i <= 1000; i++)
           fprintf(f, "%d\n", i);
       fclose(f);
       return 0;
   }
   

2. #include <stdio.h>
   
   void
   count(char *filename) {
       int characters = 0;
       int lines = 0;
       int ch;
       FILE *f;
       
       f = fopen(filename, "r");
       if (f == NULL) {
           fprintf(stderr, "count: %s: ", filename);
           perror("");
           return;
       }
       while ((ch = fgetc(f)) != EOF) {
           characters++;
           if (ch == '\n')
               lines++;
       }
       fclose(f);
       printf("%s: %d characters %d lines\n", filename, characters, lines);
   }
   
   int
   main(int argc, char *argv[]) {
       int i;
       
       for (i = 1; i < argc; i++)
           count(argv[i]);
       return 0;
   }
   

3. #include <stdio.h>
   #include <string.h>
   #include <stdlib.h>
   #include <ctype.h>
   
   enum {
       DEFAULT_NLINES = 10,
       MAX_LINE_LENGTH = 256
   };
   
    
   void
   head(char *filename, int n_lines) {
       FILE *f;
       int  ch, lines;
       
       f = fopen(filename, "r");
       if (f == NULL) {
           fprintf(stderr, "grep: %s: ", filename);
           perror("");
           return;
       }
       lines = 0;
       while ((ch = fgetc(f)) != EOF) {
           putchar(ch);
           if (ch == '\n')
               lines++;
           if (lines >= n_lines)
               break;
       }
       fclose(f);
   }
   
   /*
    * Or using fgets which has the disadvantage 
    * of a maximum line length.
    */
   void
   head1(char *filename, int n_lines) {
       FILE *f;
       int  line_number;
       char line[MAX_LINE_LENGTH+2];
       
       f = fopen(filename, "r");
       if (f == NULL) {
           fprintf(stderr, "grep: %s: ", filename);
           perror("");
           return;
       }
       for (line_number = 0; line_number < n_lines; line_number++) {
           if (fgets(line, MAX_LINE_LENGTH, f) == NULL)
               break;
           fputs(line, stdout);
       }
       fclose(f);
   }
   
   void
   usage() {
       fprintf(stderr, "Usage: head [-n lines] ");
       exit(1);
   }
   
   int
   main(int argc, char *argv[]) {
       int n_lines = DEFAULT_NLINES;
       char *filename;
       
       if (argc != 2 && argc != 4)
           usage();
           
       if (argc == 2)
           filename = argv[1];
       else {
           if (strcmp(argv[1], "-n") != 0)
               usage();
           n_lines = atoi(argv[2]);
           filename = argv[3];
       } 
       head(filename, n_lines);
       return 0;
   }