我正在编写一个在子进程上执行word count命令的程序。父进程应该将用户输入的一系列行通过管道发送到子进程。 我试图这样做,但我最终得到了一个错误。 这是我的代码:
int main ()
{
int fd[2];
char buff;
int pid;
int pip;
pid = fork();
pip = pipe(fd);
if (pid != 0)
{
pip = pipe(fd);
if (pipe == 0)
{
while (read(fd[0], &buff,1) > 0 )
{
write (fd[1],&buff,1);
}
close(fd[0]);
_exit(0);
}
}
else
{
dup2(fd[1],1);
close(fd[1]);
execlp ("wc","wc",NULL);
_exit(-1);
}
return 0;
}
我还尝试使用dup2
将子项的标准输入与父进程创建的管道的读取描述符相关联。
但是我收到了这个错误:wc: standard input: Input/output error
。
我该如何解决?
UPDATED (错误已解决,但我获得了无限循环)
int main ()
{
int fd[2];
char buff;
int pid;
int pip;
pip = pipe(fd);
if (pip == 0)
{
pid = fork();
if (pid != 0)
{
while (read(fd[0], &buff,1) > 0 )
{
write (fd[1],&buff,1);
}
close(fd[0]);
}
else {
dup2(fd[1],1);
close(fd[1]);
execlp ("wc","wc",NULL);
_exit(-1);
}
}
return 0;
}
答案 0 :(得分:0)
#include <unistd.h>
int main ()
{
int fd[2];
char buff;
int pid;
int pip;
int status;
pip = pipe(fd);
if (pip == 0)
{
pid = fork();
if (pid != 0)
{
close(fd[0]);
while (read(0, &buff,1) > 0 )
{
write (fd[1],&buff,1); /* your old loop forwarded internally in the pipe only*/
}
close(fd[1]);
} else {
dup2(fd[0],0); /* you had dup2(fd[1], 1), replacing stdout of wc with the write end from wc */
close(fd[0]);
close(fd[1]);
execlp ("wc","wc",NULL);
_exit(-1);
}
}
wait(&status); /* reap the child process */
return 0;
}