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Annotation of cci/usr/src/man/man2/dup.2, revision 1.1.1.1

1.1       root        1: .TH DUP 2 "12 February 1983"
                      2: .UC 4
                      3: .SH NAME
                      4: dup, dup2 \- duplicate a descriptor
                      5: .SH SYNOPSIS
                      6: .nf
                      7: .ft B
                      8: newd = dup(oldd)
                      9: int newd, oldd;
                     10: .PP
                     11: .ft B
                     12: dup2(oldd, newd)
                     13: int oldd, newd;
                     14: .fi
                     15: .SH DESCRIPTION
                     16: .I Dup
                     17: duplicates an existing object descriptor.
                     18: The argument \fIoldd\fP is a small non-negative integer index in
                     19: the per-process descriptor table.  The value must be less
                     20: than the size of the table, which is returned by
                     21: .IR getdtablesize (2).
                     22: The new descriptor
                     23: .I newd
                     24: returned by the call is the lowest numbered descriptor which is
                     25: not currently in use by the process.
                     26: .PP
                     27: The object referenced by the descriptor does not distinguish
                     28: between references using \fIoldd\fP and \fInewd\fP in any way.
                     29: Thus if \fInewd\fP and \fIoldd\fP are duplicate references to an open
                     30: file,
                     31: .IR read (2),
                     32: .IR write (2)
                     33: and
                     34: .IR lseek (2)
                     35: calls all move a single pointer into the file.
                     36: If a separate pointer into the file is desired, a different
                     37: object reference to the file must be obtained by issuing an
                     38: additional
                     39: .IR open (2)
                     40: call.
                     41: .PP
                     42: In the second form of the call, the value of
                     43: .IR newd
                     44: desired is specified.  If this descriptor is already
                     45: in use, the descriptor is first deallocated as if a
                     46: .IR close (2)
                     47: call had been done first.
                     48: .SH "RETURN VALUE
                     49: The value \-1 is returned if an error occurs in either call.
                     50: The external variable
                     51: .I errno
                     52: indicates the cause of the error.
                     53: .SH "ERRORS
                     54: .I Dup
                     55: and
                     56: .I dup2
                     57: fail if:
                     58: .TP 15
                     59: [EBADF]
                     60: \fIOldd\fP or
                     61: \fInewd\fP is not a valid active descriptor
                     62: .TP 15
                     63: [EMFILE]
                     64: Too many descriptors are active.
                     65: .SH "SEE ALSO"
                     66: accept(2),
                     67: open(2),
                     68: close(2),
                     69: pipe(2),
                     70: socket(2),
                     71: socketpair(2),
                     72: getdtablesize(2)

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