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Reordered text in DESCRIPTION and added some details for dup2().

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Michael Kerrisk 2008-01-12 13:19:03 +00:00
parent fd48405669
commit a4e3b1bc3e
1 changed files with 30 additions and 10 deletions
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man2/dup.2
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@ -1,7 +1,8 @@
.\" Hey Emacs! This file is -*- nroff -*- source.
.\"
.\" This manpage is Copyright (C) 1992 Drew Eckhardt;
.\" 1993 Michael Haardt, Ian Jackson.
.\" and Copyright (C) 1993 Michael Haardt, Ian Jackson.
.\" and Copyright (C) 2005, 2008 Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
@ -28,8 +29,10 @@
.\" Fixed typoes.
.\" Modified 1997-01-31, Eric S. Raymond <esr@thyrsus.com>
.\" Modified 2002-09-28, aeb
.\" 2009-01-12, mtk, reordered text in DESCRIPTION and added some
.\" details for dup2().
.\"
.TH DUP 2 1994-08-21 "Linux" "Linux Programmer's Manual"
.TH DUP 2 2008-01-12 "Linux" "Linux Programmer's Manual"
.SH NAME
dup, dup2 \- duplicate a file descriptor
.SH SYNOPSIS
@ -46,6 +49,30 @@ and
create a copy of the file descriptor
.IR oldfd .
.BR dup ()
uses the lowest-numbered unused descriptor for the new descriptor.
.BR dup2 ()
.RI "makes " newfd " be the copy of " oldfd ", closing " newfd
first if necessary, but note the following:
.IP * 3
If
.I olfd
is not a valid file descriptor, then the call fails, and
.I newfd
is not closed.
.IP *
If
.I oldfd
is a valid file descriptor, and
.I newfd
has the same value as
.IR oldfd ,
then
.BR dup2 ()
does nothing, and returns
.IR newfd .
.PP
After a successful return from
.BR dup ()
or
@ -65,13 +92,6 @@ The close-on-exec flag
see
.BR fcntl (2))
for the duplicate descriptor is off.
.BR dup ()
uses the lowest-numbered unused descriptor for the new descriptor.
.BR dup2 ()
.RI "makes " newfd " be the copy of " oldfd ", closing " newfd
first if necessary.
.SH "RETURN VALUE"
.BR dup ()
and
@ -127,7 +147,7 @@ If
.I newfd
was open, any errors that would have been reported at
.BR close (2)
time, are lost.
time are lost.
A careful programmer will not use
.BR dup2 ()
without closing