$home/manuals/plan9_4th/2/dup

DUP(2)                        System Calls Manual                       DUP(2)



NAME
       dup - duplicate an open file descriptor

SYNOPSIS
       #include <u.h>
       #include <libc.h>

       int dup(int oldfd, int newfd)

DESCRIPTION
       Given  a file descriptor, oldfd, referring to an open file, dup returns
       a new file descriptor referring to the same file.

       If newfd is -1 the system chooses the lowest available file descriptor.
       Otherwise,  dup will use newfd for the new file descriptor (closing any
       old file associated with newfd).  File descriptors are allocated dynam‐
       ically,  so to prevent unwarranted growth of the file descriptor table,
       dup requires that newfd be no greater than 20  more  than  the  highest
       file descriptor ever used by the program.

SOURCE
       /sys/src/libc/9syscall

SEE ALSO
       intro(2), dup(3)

DIAGNOSTICS
       Sets errstr.



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