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diff --git a/man3p/vfork.3p b/man3p/vfork.3p new file mode 100644 index 000000000..533636e68 --- /dev/null +++ b/man3p/vfork.3p @@ -0,0 +1,113 @@ +.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved +.TH "VFORK" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual" +.\" vfork +.SH NAME +vfork \- create a new process; share virtual memory +.SH SYNOPSIS +.LP +\fB#include <unistd.h> +.br +.sp +pid_t vfork(void); \fP +\fB +.br +\fP +.SH DESCRIPTION +.LP +The \fIvfork\fP() function shall be equivalent to \fIfork\fP(), except +that the behavior +is undefined if the process created by \fIvfork\fP() either modifies +any data other than a variable of type \fBpid_t\fP used to +store the return value from \fIvfork\fP(), or returns from the function +in which \fIvfork\fP() was called, or calls any other +function before successfully calling \fI_exit\fP() or one of the \fIexec\fP +family of functions. +.SH RETURN VALUE +.LP +Upon successful completion, \fIvfork\fP() shall return 0 to the child +process and return the process ID of the child process to +the parent process. Otherwise, -1 shall be returned to the parent, +no child process shall be created, and \fIerrno\fP shall be set +to indicate the error. +.SH ERRORS +.LP +The \fIvfork\fP() function shall fail if: +.TP 7 +.B EAGAIN +The system-wide limit on the total number of processes under execution +would be exceeded, or the system-imposed limit on the +total number of processes under execution by a single user would be +exceeded. +.TP 7 +.B ENOMEM +There is insufficient swap space for the new process. +.sp +.LP +\fIThe following sections are informative.\fP +.SH EXAMPLES +.LP +None. +.SH APPLICATION USAGE +.LP +Conforming applications are recommended not to depend on \fIvfork\fP(), +but to use \fIfork\fP() instead. The \fIvfork\fP() function may be +withdrawn in a future version. +.LP +On some implementations, \fIvfork\fP() is equivalent to \fIfork\fP(). +.LP +The \fIvfork\fP() function differs from \fIfork\fP() only in that +the child process can +share code and data with the calling process (parent process). This +speeds cloning activity significantly at a risk to the +integrity of the parent process if \fIvfork\fP() is misused. +.LP +The use of \fIvfork\fP() for any purpose except as a prelude to an +immediate call to a function from the \fIexec\fP family, or to \fI_exit\fP(), +is not advised. +.LP +The \fIvfork\fP() function can be used to create new processes without +fully copying the address space of the old process. If a +forked process is simply going to call \fIexec\fP, the data space +copied from the parent to +the child by \fIfork\fP() is not used. This is particularly inefficient +in a paged +environment, making \fIvfork\fP() particularly useful. Depending upon +the size of the parent's data space, \fIvfork\fP() can give +a significant performance improvement over \fIfork\fP(). +.LP +The \fIvfork\fP() function can normally be used just like \fIfork\fP(). +It does not work, +however, to return while running in the child's context from the caller +of \fIvfork\fP() since the eventual return from +\fIvfork\fP() would then return to a no longer existent stack frame. +Care should be taken, also, to call \fI_exit\fP() rather than \fIexit\fP() +if \fIexec\fP cannot be used, since \fIexit\fP() flushes and closes +standard I/O channels, thereby damaging the parent process' standard +I/O data structures. (Even with \fIfork\fP(), it is wrong to call +\fIexit\fP(), since buffered +data would then be flushed twice.) +.LP +If signal handlers are invoked in the child process after \fIvfork\fP(), +they must follow the same rules as other code in the +child process. +.SH RATIONALE +.LP +None. +.SH FUTURE DIRECTIONS +.LP +This function may be withdrawn in a future version. +.SH SEE ALSO +.LP +\fIexec\fP() , \fIexit\fP() , \fIfork\fP() , \fIwait\fP() , the Base +Definitions volume of +IEEE\ Std\ 1003.1-2001, \fI<unistd.h>\fP +.SH COPYRIGHT +Portions of this text are reprinted and reproduced in electronic form +from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology +-- Portable Operating System Interface (POSIX), The Open Group Base +Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of +Electrical and Electronics Engineers, Inc and The Open Group. In the +event of any discrepancy between this version and the original IEEE and +The Open Group Standard, the original IEEE and The Open Group Standard +is the referee document. The original Standard can be obtained online at +http://www.opengroup.org/unix/online.html . |