NAME

dup − dups of open files

SYNOPSIS

bind #d /fd
 /fd/0
/fd/0ctl
/fd/1
/fd/1ctl
...

DESCRIPTION

The dup device serves a one-level directory containing files whose names are decimal numbers.  Each such file also has an associated control file.  A file of name n corresponds to open file descriptor n in the current process. 

A sys-open(2) of file n results in a file descriptor identical to what would be returned from a system call sys->dup(n, -1).  Note that the result is no longer a file in the dup device. 

The stat operation returns information about the device file, not the open file it points to.  A stat of #d/n will contain n for the name, 0 for the length, and 400, 200, or 600 (octal) for the mode, depending on whether the dup target is open for reading, writing, or both. 

A file of name nctl may be read to discover the properties of the associated file descriptor, in format identical to that of the fd file in prog(3).

SEE ALSO

sys-dup(2)

SOURCE

/usr/inferno/emu/port/devdup.c
/usr/inferno/os/port/devdup.c