#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>

#define oops(m) do{perror(m); exit(1);}while(0)

int main()
{
char buf[32];
int pid = 0;
int num = 0;
int i = 0;
int flag = 0;
char * p = NULL;

while (1)
{
flag = 0;
i = 0;
num = 0;

printf("Please input a cmd: ");
fgets(buf, 32, stdin);

if (strncmp(buf, "end", 3) == 0)
break;

p = strstr(buf, "\n");
if (p != NULL)
*p = '\0';

while (buf[i] != '\0')
{
if (buf[i] == ' ' && buf[i+1] != ' ')
{
num++;//这里不懂
flag = 1;//还有这里，所谓的标记，是什么意思
}
else
flag = 0;//???

i++;
}

char* argv[num+2];// 为什么又是+2
argv[num+1] = NULL;

p = buf;
for (i = 0; i < num+1; i++)
{
argv[i] = p;
p = strstr(p, " ");

if (p == NULL)
break;

while (*p == ' ' && *(p+1) == ' ')
{   
*p = '\0';
p++;
}   
*p = '\0';
p++;
}

pid = fork();
if (pid == -1)
{
oops("fork");
}
else if (pid == 0)
{
execvp(argv[0], argv);
perror("execvp");
}

wait(NULL);
}


return 0;
}


其他的都还懂

求高手指教，注释部分不懂，其它的都还好

问题是那些不懂的，使得整个代码不连贯

这几天都搞的忘记了