1 cfa37a7b 2004-04-10 devnull .TH DUP 3
 2 cfa37a7b 2004-04-10 devnull .SH NAME
 3 cfa37a7b 2004-04-10 devnull dup \- duplicate an open file descriptor
 4 cfa37a7b 2004-04-10 devnull .SH SYNOPSIS
 5 cfa37a7b 2004-04-10 devnull .B #include <u.h>
 6 cfa37a7b 2004-04-10 devnull .br
 7 cfa37a7b 2004-04-10 devnull .B #include <libc.h>
 8 cfa37a7b 2004-04-10 devnull .PP
 9 cfa37a7b 2004-04-10 devnull .B
10 cfa37a7b 2004-04-10 devnull int dup(int oldfd, int newfd)
11 cfa37a7b 2004-04-10 devnull .SH DESCRIPTION
12 cfa37a7b 2004-04-10 devnull Given a file descriptor,
13 cfa37a7b 2004-04-10 devnull .IR oldfd ,
14 cfa37a7b 2004-04-10 devnull referring to an open file,
15 cfa37a7b 2004-04-10 devnull .I dup
16 cfa37a7b 2004-04-10 devnull returns a new file descriptor referring to the same file.
17 cfa37a7b 2004-04-10 devnull .PP
18 cfa37a7b 2004-04-10 devnull If
19 cfa37a7b 2004-04-10 devnull .I newfd
20 cfa37a7b 2004-04-10 devnull is \-1 the system chooses the lowest available file descriptor.
21 cfa37a7b 2004-04-10 devnull Otherwise,
22 cfa37a7b 2004-04-10 devnull .I dup
23 cfa37a7b 2004-04-10 devnull will use
24 cfa37a7b 2004-04-10 devnull .I newfd
25 cfa37a7b 2004-04-10 devnull for the new file descriptor
26 cfa37a7b 2004-04-10 devnull (closing any old file associated with
27 cfa37a7b 2004-04-10 devnull .IR newfd ).
28 cfa37a7b 2004-04-10 devnull File descriptors are allocated dynamically,
29 cfa37a7b 2004-04-10 devnull so to prevent unwarranted growth of the file descriptor table,
30 cfa37a7b 2004-04-10 devnull .I dup
31 cfa37a7b 2004-04-10 devnull requires that
32 cfa37a7b 2004-04-10 devnull .I newfd
33 cfa37a7b 2004-04-10 devnull be no greater than 20 more than the highest file descriptor ever used by
34 cfa37a7b 2004-04-10 devnull the program.
35 cfa37a7b 2004-04-10 devnull .SH SOURCE
36 b5fdffee 2004-04-19 devnull .B /usr/local/plan9/src/libc/9syscall
37 cfa37a7b 2004-04-10 devnull .SH SEE ALSO
38 bf8a59fa 2004-04-11 devnull .IR intro (3),
39 cfa37a7b 2004-04-10 devnull .IR dup (3)
40 cfa37a7b 2004-04-10 devnull .SH DIAGNOSTICS
41 cfa37a7b 2004-04-10 devnull Sets
42 cfa37a7b 2004-04-10 devnull .IR errstr .