NOTES: since glibc 2.3.3, the glibc NPTL fork() wrapper bypasses the

fork() system call to invoke clone() with appropriate flags.

man2/fork.2

@@ -36,7 +36,7 @@
 .\"     Greatly expanded, to describe all attributes that differ
 .\"	parent and child.
 .\"
-.TH FORK 2 2008-01-13 "Linux" "Linux Programmer's Manual"
+.TH FORK 2 2008-04-22 "Linux" "Linux Programmer's Manual"
 .SH NAME
 fork \- create a child process
 .SH SYNOPSIS
@@ -191,6 +191,22 @@ Under Linux,
 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.
+
+Since version 2.3.3,
+.\" nptl/sysdeps/unix/sysv/linux/fork.c
+rather than invoking the kernel's
+.BR fork ()
+system call,
+the glibc
+.BR fork ()
+wrapper that is provided as part of the
+NPTL threading implementation invokes
+.BR clone (2)
+with flags that provide the same effect as the traditional system call.
+The glibc wrapper invokes any fork handlers that have been
+have been established using
+.BR pthread_atfork (3).
+.\" and does some magic to ensure that getpid(2) returns the right value.
 .SH EXAMPLE
 See
 .BR pipe (2)