bsd/man/man4/fd.4

   1 .\"     $NetBSD: fd.4,v 1.3 1994/11/30 16:22:13 jtc Exp $
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  34 .\"     @(#)fd.4        8.1 (Berkeley) 6/9/93
  35 .\"
  36 .Dd June 9, 1993
  37 .Dt FD 4
  38 .Os
  39 .Sh NAME
  40 .Nm fd ,
  41 .Nm stdin ,
  42 .Nm stdout ,
  43 .Nm stderr
  44 .Nd file descriptor files
  45 .Sh DESCRIPTION
  46 The files
  47 .Pa /dev/fd/0
  48 through
  49 .Pa /dev/fd/#
  50 refer to file descriptors which can be accessed through the file
  51 system.
  52 If the file descriptor is open and the mode the file is being opened
  53 with is a subset of the mode of the existing descriptor, the call:
  54 .Bd -literal -offset indent
  55 fd = open("/dev/fd/0", mode);
  56 .Ed
  57 .Pp
  58 and the call:
  59 .Bd -literal -offset indent
  60 fd = fcntl(0, F_DUPFD, 0);
  61 .Ed
  62 .Pp
  63 are equivalent.
  64 .Pp
  65 Opening the files
  66 .Pa /dev/stdin ,
  67 .Pa /dev/stdout
  68 and
  69 .Pa /dev/stderr
  70 is equivalent to the following calls:
  71 .Bd -literal -offset indent
  72 fd = fcntl(STDIN_FILENO,  F_DUPFD, 0);
  73 fd = fcntl(STDOUT_FILENO, F_DUPFD, 0);
  74 fd = fcntl(STDERR_FILENO, F_DUPFD, 0);
  75 .Ed
  76 .Pp
  77 Flags to the
  78 .Xr open 2
  79 call other than
  80 .Dv O_RDONLY ,
  81 .Dv O_WRONLY
  82 and
  83 .Dv O_RDWR
  84 are ignored.
  85 .Sh FILES
  86 .Bl -tag -width /dev/stderr -compact
  87 .It Pa /dev/fd/#
  88 .It Pa /dev/stdin
  89 .It Pa /dev/stdout
  90 .It Pa /dev/stderr
  91 .El
  92 .Sh SEE ALSO
  93 .Xr tty 4