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 execution, 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 cre-

ated, 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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