fork - phpMan

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
       incurred by fork is the time and memory required to  duplicate  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 exe-
       cution, and a 0 is returned in the child’s thread of execution.  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.

       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, BSD 4.3.

SEE ALSO
       clone(2), execve(2), vfork(2), wait(2)



Linux 1.2.9                       1995-06-10                           FORK(2)

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