小白學(xué)編程7：代碼復(fù)用，理解函數(shù)
《小白學(xué)編程》第七講的相關(guān)代碼：
#include <stdio.h>
int gd_square(int x)
{
??return x*x;
}
int main()
{
??int n = 88;
??printf("square of %d is %d\n", n, gd_square(n));
??return 0;
}
~
#include <stdio.h>
int main(int argc, const char* argv[])
{
??printf("main received %d arguments\n", argc);
??for(int i = 0; i < argc; i++) {
????printf("argv[%d] = %s\n", i, argv[i]);
??}
??return 0;
}
#include <stdio.h>
int usage()
{
??printf("gdplay %d.%d, a utility just for fun\n"
??????"\tgdplay [options]\n"
??????"\t supported options:\n"
??????"\t -h show this help\n"
??????"\t -t print time\n", VER_MAJOR, VER_MINOR);
}
void gd_time()
{
}
int main(int argc, const char* argv[])
{
??printf("main received %d arguments\n", argc);
??for(int i = 0; i < argc; i++) {
????printf("argv[%d] = %s\n", i, argv[i]);
??}
??if(argc <= 1)
????return usage();
??if(argv[1][0] == '-') {
????switch(argv[1][1]) {
??????case?'h':
????????return usage();
??????case?'t':
????????gd_time();
????????break;
????}
??}
??return 0;
}
#define VER_MAJOR 0
#define VER_MINOR 1
geduer@gdk8:~/clabs$ cat lab5-3.c
#include <stdio.h>
#include <time.h>
#define VER_MAJOR 0
#define VER_MINOR 1
int usage(const char* msg)
{
??if(msg != NULL) {
??????printf("error: %s\n", msg);
??}
??printf("gdplay %d.%d, a utility just for fun\n"
??????"syntax: gdplay [options]\n"
??????"\tsupported options:\n"
??????"\t-h show this help\n"
??????"\t-t print time\n", VER_MAJOR, VER_MINOR);
}
void gd_time()
{
??time_t now;
??struct tm* tminfo;
??char buffer[80];
??time(&now);
??tminfo = localtime(&now);
??strftime(buffer, sizeof(buffer), "%F %h %H:%M:%S %p %c", tminfo);
??puts(buffer);
}
int main(int argc, const char* argv[])
{
??printf("main received %d arguments\n", argc);
??for(int i = 0; i < argc; i++) {
????printf("argv[%d] = %s\n", i, argv[i]);
??}
??if(argc <= 1)
????return usage("missing arguments");
??if(argv[1][0] == '-') {
????switch(argv[1][1]) {
??????case?'h':
????????return usage(NULL);
??????case?'t':
????????gd_time();
????????break;
????}
??}
??return 0;
}
