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.TH uopen 1 "5 May 2005" "Straylight/Edgeware" "Preload hacks"
.SH NAME
uopen \- connect to Unix-domain sockets using open(2)
.SH SYNOPSIS
.B uopen
.RI [ command
.RI [ args ...]]
.SH DESCRIPTION
The
.B uopen
command runs
.I command
(by default, the calling user's shell, as determined by the
.B SHELL
environment variable) in an environment where an attempt by the program
to
.BR open (2)
a Unix-domain socket results in a connection being made to the socket.
.PP
This might be used to implement a signature server which chooses a
random signature for newly-written news and mail messages.  This can be
done by writing a simple program to choose and print a signature,
causing it to be invoked in response to connections to the socket
.B $HOME/.signature
(for example, by
.BR fw (1))
and running the message-drafting program under the control of
.BR uopen .
If we were willing to accept
.BR fortune (5)
as our signature generator, this can be done using, say
.VS
fw -d -p$HOME/.sigd.pid \e
  "from unix:$HOME/.signature to exec[fortune -s]"
uopen emacs -nw -f vm
.VE
.SH BUGS
.B uopen
is implemented as an
.B LD_PRELOAD
hack.  It won't work on setuid programs.
.PP
The code is needlessly Linux-specific in some places. 
.PP
It may not catch some uses of
.BR open (2)
or its friends from inside the Linux C library.  It's a strange and
murky world in there, and glibc does all manner of strange linker tricks
to stop you messing with
.BR open (2).
.SH SEE ALSO
.BR fw (1),
.BR ld.so (8),
.BR open (2).
.SH AUTHOR
Mark Wooding, <mdw@distorted.org.uk>