Week 3 Tutorial — Sample Solutions

    1. sum3str.c 

      // sum3str.c: sum 3 hardcoded strings
#include <stdio.h>
#include <stdlib.h>

int main() {
   char *r = "1";
   char *s = "23";
   char *t = "456";
   int i, j, k;
   if ((sscanf(r, "%d", &i) == 1) &&
       (sscanf(s, "%d", &j) == 1) &&
       (sscanf(t, "%d", &k) == 1)) {
      printf("%d\n", i+j+k);
  }
  return EXIT_SUCCESS;
}

    2. sum3arg.c 

      // sum3arg.c: sum 3 arguments from the command line
#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[]) {
   int i, j, k;
   if ((argc == 4) &&
      (sscanf(argv[1], "%d", &i) == 1) &&
      (sscanf(argv[2], "%d", &j) == 1) &&
      (sscanf(argv[3], "%d", &k) == 1)) {
      printf("%d\n", i+j+k);
   }
   return EXIT_SUCCESS;
}


    1. target: list of dependent files
	command

    2. tab

    3. The command gcc -Wall -Werror -o myprog myprog.c will be executed.

    4. No action is taken. The following message will be generated. 
      make: `myprog' is up to date.

      1. gcc -Wall -Werror -O -o prog1 prog1.c
      2. gcc -Wall -Werror -O -o prog2 prog2.c
      3. gcc -Wall -Werror -O -o prog1 prog1.c 

    2. CC=gcc
CFLAGS=-Wall -Werror -O

prog1: prog1.c prog1.h
	$(CC) $(CFLAGS) -o prog1 prog1.c

prog2: prog2.c prog2.h
	$(CC) $(CFLAGS) -o prog2 prog2.c

all: prog1 prog2

clean:
	rm -f prog1.o prog2.o prog1 prog2 core

    3. The user can 'force' a rule for a target to be executed by 'touching' one of its dependent files.

    4. The commands for both targets prog1 and prog2 will be executed.

    5. CC=gcc
CFLAGS=-Wall -Werror -O

prog1: prog1.c prog1.h
	$(CC) $(CFLAGS) -o $@ $<

prog2: prog2.c prog2.h
	$(CC) $(CFLAGS) -o $@ $<

all: prog1 prog2

clean:
	rm -f prog1.o prog2.o prog1 prog2 core