221 lines
4.9 KiB
Groff
221 lines
4.9 KiB
Groff
.\" $NetBSD: rmtops.3,v 1.3 1998/03/08 23:36:46 mrg Exp $
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.\"
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.TH RMTOPS 3
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.SH NAME
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rmtops \- access tape drives on remote machines
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.SH SYNOPSIS
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.nf
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.ft B
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#include <rmt.h>
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#include <sys/stat.h> /* MUST come after <rmt.h> */
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int isrmt (fd)
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int fd;
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int rmtaccess (file, mode)
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char *file;
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int mode;
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int rmtclose (fd)
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int fd;
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int rmtcreat (file, mode)
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char *file;
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int mode;
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int rmtdup (fd)
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int fd;
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int rmtfcntl (fd, cmd, arg)
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int fd, cmd, arg;
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int rmtfstat (fd, buf)
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int fd;
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struct stat *buf;
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int rmtioctl (fd, request, argp)
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int fd, request;
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char *argp;
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int rmtisatty (fd)
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int fd;
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long rmtlseek (fd, offset, whence)
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int fd, whence;
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long offset;
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int rmtlstat (file, buf)
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char *file;
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struct stat *buf;
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int rmtopen (file, flags [, mode])
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char *file;
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int flags, mode;
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int rmtread (fd, buf, nbytes)
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int fd, nbytes;
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char *buf;
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int rmtstat (file, buf)
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char *file;
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struct stat *buf;
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int rmtwrite (fd, buf, nbytes)
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int fd, nbytes;
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char *buf;
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.fi
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.ft R
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.SH DESCRIPTION
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.I Rmtops
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provides a simple means of transparently accessing tape drives
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on remote machines over the ethernet, via
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.IR rsh (1)
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and
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.IR rmt (8).
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These routines are used like their corresponding
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system calls, but allow the user to open up a tape drive on a remote
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system on which he or she has an account and the appropriate remote
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permissions.
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.PP
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A remote tape drive file name has the form
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.sp
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.RS
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.RI [ user @] system :/dev/???
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.RE
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.sp
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where
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.I system
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is the remote system,
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.I /dev/???
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is the particular drive on the remote system (raw, blocked, rewinding,
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non-rewinding, etc.), and the optional
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.I user
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is the login name to be used on the remote system, if different from
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the current user's login name.
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.PP
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The library source code may be optionally compiled to recognize the
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old, 4.2 BSD, remote syntax
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.sp
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.RS
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.IR system [. user ]:/dev/???
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.RE
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.sp
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By default, only the first form (introduced in 4.3 BSD) is recognized.
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.PP
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For transparency, the user should include the file
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.IR <rmt.h> ,
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which has the following defines in it:
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.PP
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.nf
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#define access rmtaccess
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#define close rmtclose
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#define creat rmtcreat
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#define dup rmtdup
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#define fcntl rmtfcntl
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#define fstat rmtfstat
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#define ioctl rmtioctl
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#define isatty rmtisatty
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#define lseek rmtlseek
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#define lstat rmtlstat
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#define open rmtopen
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#define read rmtread
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#define stat rmtstat
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#define write rmtwrite
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.fi
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.PP
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This allows the programmer to use
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.IR open ,
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.IR close ,
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.IR read ,
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.IR write ,
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etc. in their normal fashion, with the
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.I rmtops
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routines taking care of differentiating between local and remote files.
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This file should be included
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.I before
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including the file
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.IR <sys/stat.h> ,
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since it redefines the identifier ``stat,'' which is used to declare
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objects of type
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.BR "struct stat" .
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.PP
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The routines differentiate between local and remote file descriptors by
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adding a bias (currently 128) to the file descriptor of the pipe.
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The programmer, if he or she must know if a file is remote, should use the
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.I isrmt
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function.
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.SH FILES
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.TP
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.B /usr/lib/librmt.a
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Contains the remote tape library. To include the library with a program,
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add the flag
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.B \-lrmt
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to the
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.IR cc (1)
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command line.
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.SH SEE ALSO
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.IR rcp (1),
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.IR rsh (1),
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.IR rmt (8),
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and the appropriate system calls in section 2.
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.SH DIAGNOSTICS
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Several of these routines will return \-1 and set
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.I errno
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to EOPNOTSUPP, if they are given a remote file name or a file descriptor
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on an open remote file (e.g.,
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.IR rmtdup ).
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.SH BUGS
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See \s-1DIAGNOSTICS\s+1 above. It is to be hoped that true remote file systems
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will eventually appear, and eliminate the need for these routines.
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.PP
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There is no way to use remote tape drives with the
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.IR stdio (3)
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package, short of recompiling it entirely to use these routines.
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.PP
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The
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.IR rmt (8)
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protocol is not very capable. In particular, it relies on
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TCP/IP sockets for error free transmission, and does no data validation
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of its own.
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.SH CONFIGURATION OPTIONS
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The library may be compiled to allow the use of 4.2 BSD style remote
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file names. This is not recommended.
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.PP
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By default, the library opens two pipes to
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.IR rsh (1).
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It may optionally be compiled to use
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.IR rexec (3),
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instead. Doing so requires the use of a
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.I .netrc
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file in the user's home directory, or that the application designer
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be willing to have
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.I rexec
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prompt the user for a login name and password on the remote host.
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.SH ENVIRONMENT
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The
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.I RCMD_CMD
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environment variable can be set to the name or pathname of a program
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to use, instead of
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.P /usr/bin/rsh ,
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and must have the same calling conventions as
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.IR rsh(1).
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.SH AUTHORS
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Jeff Lee (gatech!jeff) wrote the original routines for accessing
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tape drives via
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.IR rmt (8).
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.PP
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Fred Fish (unisoft!fnf) redid them into a general purpose library.
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.PP
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Arnold Robbins
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(formerly gatech!arnold, now emory!arnold)
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added the ability to specify a user
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name on the remote system, the
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.B <rmt.h>
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include file, this man page,
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cleaned up the library a little,
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and made the appropriate changes for 4.3 BSD.
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.PP
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Dan Kegel (srs!dan) contributed the code to use
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.IR rexec (3)
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library routine.
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