Unix реализация конвейера на C

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#include <sys/types.h>

#include <unistd.h>

#include <stdio.h>



int main

{

  int fd[2];

  pipe(fd);

  if (fork

  {

    dup2(fd[1], 1);

    close(fd[1]);

    close(fd[0]);

    execlp("ls", "ls", (char*)0);

  }

  else

  {

    dup2(fd[0], 0);

    close(fd[0]);

    close(fd[1]);

    execlp("wc", "wc", (char*)0);

  }

  return 0;

}

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FORK(2)                    Linux Programmer’s Manual                   FORK(2)



NAME

       fork - create a child process



SYNOPSIS

       #include <sys/types.h>

       #include <unistd.h>



       pid_t fork(void);



DESCRIPTION

       fork  creates  a  child  process that differs from the parent process

       only in its PID and PPID, and in the fact  that  resource  utilizations

       are set to 0.  File locks and pending signals are not inherited.



       Under  Linux,  fork  is implemented using copy-on-write pages, so the

       only penalty that it incurs is the time and memory required  to  dupli&#8208;

       cate  the  parent’s  page tables, and to create a unique task structure

       for the child.



RETURN VALUE

       On success, the PID of the child process is returned  in  the  parent’s

       thread  of execution, and a 0 is returned in the child’s thread of exe&#8208;

       cution.  On failure, a -1 will be returned in the parent’s context,  no

       child process will be created, and errno will be set appropriately.



ERRORS

       EAGAIN fork  cannot  allocate  sufficient memory to copy the parent’s

              page tables and allocate a task structure for the child.



       EAGAIN It was not possible to create a new process because the caller’s

              RLIMIT_NPROC  resource  limit  was  encountered.  To exceed this

              limit, the process must have either  the  CAP_SYS_ADMIN  or  the

              CAP_SYS_RESOURCE capability.



       ENOMEM fork  failed  to  allocate  the  necessary  kernel  structures

              because memory is tight.



CONFORMING TO

       The fork call conforms to SVr4, SVID, POSIX, X/OPEN, 4.3BSD.



EXAMPLE

       See pipe(2) and wait(2).



SEE ALSO

       clone(2 execve(2 setrlimit(2 unshare(2 vfork(2 wait(2 capa&#8208;

       bilities(7)



Linux 2.6.6                       2004-05-27                           FORK(2)