| .TH DUP 3 |
| .SH NAME |
| dup \- duplicate an open file descriptor |
| .SH SYNOPSIS |
| .B #include <u.h> |
| .br |
| .B #include <libc.h> |
| .PP |
| .B |
| int dup(int oldfd, int newfd) |
| .SH DESCRIPTION |
| Given a file descriptor, |
| .IR oldfd , |
| referring to an open file, |
| .I dup |
| returns a new file descriptor referring to the same file. |
| .PP |
| If |
| .I newfd |
| is \-1 the system chooses the lowest available file descriptor. |
| Otherwise, |
| .I dup |
| will use |
| .I newfd |
| for the new file descriptor |
| (closing any old file associated with |
| .IR newfd ). |
| .SH SOURCE |
| .B \*9/src/lib9/dup.c |
| .SH DIAGNOSTICS |
| Sets |
| .IR errstr . |
| .SH BUGS |
| To avoid name conflicts with the underlying system, |
| .I dup |
| is a preprocessor macro defined as |
| .IR p9dup ; |
| see |
| .IR intro (3). |
