NAME

sigrand.go -- a Go port of tomc's classic sigrand.pl

DESCRIPTION

The format of the sigfile takes advantage of Perl's $/ special var, which allows you to change the line separator when reading from filehandles using the <> operator.

Since Go doesn't offer this syntax sugar, the file is read in a coroutine and complete, %%-separated records are pushed through a chan string to be iterated over with range in the reader logic.

The %% record separator is currently hard-coded, but could be trivially factored out, though the scanner is still pretty line-oriented. Exercise for the reader!

OVERVIEW

The original version of the script functioned somewhat like a daemon and was often invoked and immediately backgrounded in a .bashrc or similar startup script.

However, I've added a bit of logging (if only to analyze the quote selection logic) and it could be a bit noisy of not detached from stdout. Nevertheless, the operation is deceptively simple:

sigrand loads, ...
... looks for a pidfile
... checks for a Unix named pipe at $HOME/.signature
... opens the pipe, blocking and waiting for someone to read
When a process reads from the pipe, sigrand ...
... opens the sigfile ("database" of signatures) at $HOME/.sigfile
... iterates over each record, selecting one at random
... writes the selected record to the pipe
... closes the pipe
... waits a split second for the reader to close as well
... repeats

To stop the sigrand process, you have two options:

Send a keyboard interrupt (^C) on the process's stdin
send a TERM signal to the pid in $HOME/.sigrandpid

EXAMPLE

First Time Setup

$ go build && cp sigrand /usr/local/bin
$ cp sigfile ~/.sigfile
$ mkfifo -m 600 ~/.signature ./sigrand

In Regular Use

In one shell session:

$ sigrand
2020/12/23 00:06:32 Opening /Users/penryu/.signature
2020/12/23 00:06:34 ++-----+---------+--------------------------------+------------
2020/12/23 00:06:34 Writing quote
2020/12/23 00:06:34 Starting over...
2020/12/23 00:06:34 Opening /Users/penryu/.signature

In other shells or processes, simply read from ~/.signature:

$ cat ~/.signature
"What duck?"
        -- (Terry Pratchett, Soul Music)
$

(The default sigfile is just a bunch of Terry Pratchett quotes.)

See start.sh for another example use.

THE ORIGINAL

The original can be found in The Perl Cookbook, and versions of it are scattered throughout the Interwebs.

COPYRIGHT

This code is licensed under the terms of the Artistic License.

penryu/sigrand