为什么 execvp 没有写入重定向的 STDOUT？我尝试在这个块中使用 printf() 作为测试，它准确地写入了它应该写入的位置，即我将 STDOUT 重定向到的文件中。
编辑：我更改了代码，并添加了 makesubcommand 的实现，并添加了一些调试消息。
pid = fork();
wait(0);
if(pid == 0)
{
fd = open(subargs[next_redirect + 1], O_CREAT|O_TRUNC|O_WRONLY, 0644);
dup2(fd, STDOUT_FILENO);
close(fd);
//create sub-command
int val = (next_redirect - (last_redirect + 1));
fprintf(stderr,"subcommand will have %i indexes\n", val);
char* subcommand[val];
makesubcommand(subcommand, subargs, last_redirect + 1, next_redirect);
execvp(subcommand[0], subcommand);
fprintf(stderr,"execvp failed\n");
}
last_redirect = next_redirect;
next_redirect = getnextredirect(subargs, last_redirect+2, subargc);
继承人 makesubcommand(4):
void makesubcommand(char** newcommand, char** oldcommand, int lowerbound, int upperbound)
{
int i;
fprintf(stderr, "lowerbound: %i upperbound: %i\n",lowerbound, upperbound);
for(i = lowerbound; i < upperbound; i++)
{
fprintf(stderr,"subarg[%i]: %s\n", (i-lowerbound), oldcommand[i]);
newcommand[i - lowerbound] = oldcommand[i];
}
for(i = lowerbound; i < upperbound; i++)
{
fprintf(stderr, "newcommand[%i] = %s\n",(i - lowerbound), newcommand[i]);
}
fprintf(stderr, "it worked\n");
}
这是一个测试运行：
{12425}/home/chris/2240New/WMU-CS2240/A3_Shell$ ls > a
subcommand will have 1 indexes
lowerbound: 0 upperbound: 1
subarg[0]: ls
newcommand[0] = ls
it worked
execvp failed