我正在为课程作业编写一个基本的 shell，它将在给定的路径列表中找到一个命令，并执行该命令。它也用于处理管道。但是，当我派生一个子进程时，我在 gdb 中收到“写入错误：管道损坏”消息，并且程序突然终止。
我似乎无法理解为什么会发生这种情况，因为我一直对打开和关闭正确的管道持谨慎态度，并且进程分叉似乎可以按预期工作。有更多 C 和 unix 编程经验的人可以帮我诊断问题吗？我的 fork 实现/管道实现在逻辑上是否不正确？
//commands is of the format {"ls -al", "more", NULL}
//it represents commands connected by pipes, ex. ls -al | more
char **commands = parseArgv(consoleinput, SPECIAL_CHARS[4]);
int numcommands = 0;
while( commands[numcommands]!=NULL )
{
numcommands++;
}
const int numpipes = 2*(numcommands-1);
int pipefds[numpipes];
int i=0;
for(i=0; i<numpipes;i=i+2)
{
pipe(pipefds+i);
}
int pipe_w = 1;
int pipe_r = pipe_w - 3;
int curcommand = 0;
while(curcommand < numcommands)
{
if(pipe_w < numpipes)
{
//open write end
dup2(pipefds[pipe_w], 1);
}
if(pipe_r > 0)
{
//open read end
dup2(pipefds[pipe_r], 0);
}
for(i=0;i<numpipes;i++) //close off all pipes
{
close(pipefds[i]);
}
//Parse current command and Arguments into format needed by execv
char **argv = parseArgv(commands[curcommand], SPECIAL_CHARS[0]);
//findpath() replaces argv[0], i.e. command name by its full path ex. ls by /bin/ls
if(findPath(argv) == 0)
{
int child_pid = fork();
//Program crashes after this point
//Reason: /bin/ls: write error, broken pipe
if(child_pid < 0)
{
perror("fork error:");
}
else if(child_pid == 0) //fork success
{
if(execv(argv[0], argv) == -1)
{
perror("Bad command or filename:");
}
}
else
{
int child_status;
child_pid = waitpid(child_pid, &child_status, 0);
if(child_pid < 0)
{
perror("waitpid error:");
}
}
}
else
{
printf("Bad command or filename");
}
free(argv);
curcommand++;
pipe_w = pipe_w + 2;
pipe_r = pipe_r + 2;
}
//int i=0;
for(i=0;i<numpipes;i++) //close off all pipes
{
close(pipefds[i]);
}
free(commands);