1. Yung-Hsiang Lu Purdue University
How to Use argc and argv
Yung-Hsiang Lu
Purdue University

2. #include <stdio. h> #include <stdlib
#include <stdio.h> #include <stdlib.h> int main(int argc, char * * argv) { if (argc < 2) printf("Need a number\n"); return EXIT_FAILURE; } int val = strtol(argv[1], NULL, 10); val += 10; printf("argv[1] = %s\n", argv[1]); printf("val = %d\n", val); return EXIT_SUCCESS;

3. check the value use argv[1]
#include <stdio.h> #include <stdlib.h> int main(int argc, char * * argv) { if (argc < 2) printf("Need a number\n"); return EXIT_FAILURE; } int val = strtol(argv[1], NULL, 10); val += 10; printf("argv[1] = %s\n", argv[1]); printf("val = %d\n", val); return EXIT_SUCCESS;
check the value
use argv[1]

4. #include <stdio. h> #include <stdlib
#include <stdio.h> #include <stdlib.h> int main(int argc, char * * argv) { if (argc < 2) printf("Need a number\n"); return EXIT_FAILURE; } int val = strtol(argv[1], NULL, 10); val += 10; printf("argv[1] = %s\n", argv[1]); printf("val = %d\n", val); return EXIT_SUCCESS;
an error message

5. the program stops with an error
#include <stdio.h> #include <stdlib.h> int main(int argc, char * * argv) { if (argc < 2) printf("Need a number\n"); return EXIT_FAILURE; } int val = strtol(argv[1], NULL, 10); val += 10; printf("argv[1] = %s\n", argv[1]); printf("val = %d\n", val); return EXIT_SUCCESS;
the program stops with an error

6. convert argv[1] to an integer store the integer in val
#include <stdio.h> #include <stdlib.h> int main(int argc, char * * argv) { if (argc < 2) printf("Need a number\n"); return EXIT_FAILURE; } int val = strtol(argv[1], NULL, 10); val += 10; printf("argv[1] = %s\n", argv[1]); printf("val = %d\n", val); return EXIT_SUCCESS;
convert argv[1] to an integer
store the integer in val

7. #include <stdio. h> #include <stdlib
#include <stdio.h> #include <stdlib.h> int main(int argc, char * * argv) { if (argc < 2) printf("Need a number\n"); return EXIT_FAILURE; } int val = strtol(argv[1], NULL, 10); val += 10; printf("argv[1] = %s\n", argv[1]); printf("val = %d\n", val); return EXIT_SUCCESS;
add 10 to val

8. print the string argv[1] and the integer val
#include <stdio.h> #include <stdlib.h> int main(int argc, char * * argv) { if (argc < 2) printf("Need a number\n"); return EXIT_FAILURE; } int val = strtol(argv[1], NULL, 10); val += 10; printf("argv[1] = %s\n", argv[1]); printf("val = %d\n", val); return EXIT_SUCCESS;
print the string argv[1]
and the integer val

9. the program successfully prints the value
#include <stdio.h> #include <stdlib.h> int main(int argc, char * * argv) { if (argc < 2) printf("Need a number\n"); return EXIT_FAILURE; } int val = strtol(argv[1], NULL, 10); val += 10; printf("argv[1] = %s\n", argv[1]); printf("val = %d\n", val); return EXIT_SUCCESS;
the program successfully
prints the value

10. #include <stdio. h> #include <stdlib
#include <stdio.h> #include <stdlib.h> int main(int argc, char * * argv) { if (argc < 2) printf("Need a number\n"); return EXIT_FAILURE; } int val = strtol(argv[1], NULL, 10); val += 10; printf("argv[1] = %s\n", argv[1]); printf("val = %d\n", val); return EXIT_SUCCESS;