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. 

An open(2) of file ­n results in a file descriptor identical to what would be returned from a system call 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 0400, 0200, or 0600 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 proc(3).

SEE ALSO

dup(2)

SOURCE

­/sys/src/9/port/devdup.c

Plan 9  —  March 01, 2002