man.postnix Miscellaneous man pages of Plan 9 related material

     DUP(2)                                                     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 in the range of legal file descriptors
          dup will use that for the new file descriptor (closing any
          old file associated with newfd); if newfd is -1 the system
          chooses the lowest available file descriptor.

     SOURCE
          /sys/src/libc/9syscall

     SEE ALSO
          intro(2), dup(3)

     DIAGNOSTICS
          Sets errstr.

     Page 1                       Plan 9            (printed 10/29/25)