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
       that it incurs 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.

       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 pro-
              cess  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
       SVr4, 4.3BSD, POSIX.1-2001.

EXAMPLE
       See pipe(2) and wait(2).

SEE ALSO
       clone(2), execve(2), setrlimit(2), unshare(2), vfork(2), wait(2), capabilities(7)



Linux 2.6.6                       2004-05-27                           FORK(2)

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