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- .TH DUP 2
- .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 ).
- File descriptors are allocated dynamically,
- so to prevent unwarranted growth of the file descriptor table,
- .I dup
- requires that
- .I newfd
- be no greater than 20 more than the highest file descriptor ever used by
- the program.
- .SH SOURCE
- .B /sys/src/libc/9syscall
- .SH SEE ALSO
- .IR intro (2),
- .IR dup (3)
- .SH DIAGNOSTICS
- Sets
- .IR errstr .
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