📄 ch16_23.htm
字号:
<HTML><HEAD><TITLE>Recipe 16.22. Program: sigrand (Perl Cookbook)</TITLE><METANAME="DC.title"CONTENT="Perl Cookbook"><METANAME="DC.creator"CONTENT="Tom Christiansen & Nathan Torkington"><METANAME="DC.publisher"CONTENT="O'Reilly & Associates, Inc."><METANAME="DC.date"CONTENT="1999-07-02T01:44:16Z"><METANAME="DC.type"CONTENT="Text.Monograph"><METANAME="DC.format"CONTENT="text/html"SCHEME="MIME"><METANAME="DC.source"CONTENT="1-56592-243-3"SCHEME="ISBN"><METANAME="DC.language"CONTENT="en-US"><METANAME="generator"CONTENT="Jade 1.1/O'Reilly DocBook 3.0 to HTML 4.0"><LINKREV="made"HREF="mailto:online-books@oreilly.com"TITLE="Online Books Comments"><LINKREL="up"HREF="ch16_01.htm"TITLE="16. Process Management and Communication"><LINKREL="prev"HREF="ch16_22.htm"TITLE="16.21. Timing Out an Operation"><LINKREL="next"HREF="ch17_01.htm"TITLE="17. Sockets"></HEAD><BODYBGCOLOR="#FFFFFF"><img alt="Book Home" border="0" src="gifs/smbanner.gif" usemap="#banner-map" /><map name="banner-map"><area shape="rect" coords="1,-2,616,66" href="index.htm" alt="Perl Cookbook"><area shape="rect" coords="629,-11,726,25" href="jobjects/fsearch.htm" alt="Search this book" /></map><div class="navbar"><p><TABLEWIDTH="684"BORDER="0"CELLSPACING="0"CELLPADDING="0"><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="228"><ACLASS="sect1"HREF="ch16_22.htm"TITLE="16.21. Timing Out an Operation"><IMGSRC="../gifs/txtpreva.gif"ALT="Previous: 16.21. Timing Out an Operation"BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="228"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1"><ACLASS="chapter"REL="up"HREF="ch16_01.htm"TITLE="16. Process Management and Communication"></A></FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="228"><ACLASS="chapter"HREF="ch17_01.htm"TITLE="17. Sockets"><IMGSRC="../gifs/txtnexta.gif"ALT="Next: 17. Sockets"BORDER="0"></A></TD></TR></TABLE></DIV><DIVCLASS="sect1"><H2CLASS="sect1"><ACLASS="title"NAME="ch16-chap16_program_0">16.22. Program: sigrand</A></H2><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch16-pgfId-2256">Description</A></H3><PCLASS="para">The following <ACLASS="indexterm"NAME="ch16-idx-1000006436-0"></A><ACLASS="indexterm"NAME="ch16-idx-1000006436-1"></A><ACLASS="indexterm"NAME="ch16-idx-1000006436-2"></A><ACLASS="indexterm"NAME="ch16-idx-1000006436-3"></A><ACLASS="indexterm"NAME="ch16-idx-1000006436-4"></A>program gives you random signatures by using named pipes. It expects the signatures file to have records in the format of the <EMCLASS="emphasis">fortune</EM> program - that is, each possible multiline record is terminated with <CODECLASS="literal">"%%\n"</CODE>. Here's an example:</P><PRECLASS="programlisting">Make is like Pascal: everybody likes it, so they go in and change it. --Dennis Ritchie%%I eschew embedded capital letters in names; to my prose-oriented eyes,they are too awkward to read comfortably. They jangle like bad typography. --Rob Pike%%God made the integers; all else is the work of Man. --Kronecker%%I'd rather have :rofix than const. --Dennis Ritchie%%If you want to program in C, program in C. It's a nice language.I use it occasionally... :-) --Larry Wall%%Twisted cleverness is my only skill as a programmer. --Elizabeth Zwicky%%Basically, avoid comments. If your code needs a comment to be understood,it would be better to rewrite it so it's easier to understand. --Rob Pike%%Comments on data are usually much more helpful than on algorithms. --Rob Pike%% Programs that write programs are the happiest programs in the world. --Andrew Hume %%</PRE><PCLASS="para">We check whether we're already running by using a file with our PID in it. If sending a signal number 0 indicates that PID still exists (or, rarely, that something else has reused it), we just exit. We also look at the current Usenet posting to decide whether to look for a per-newsgroup signature file. That way, you can have different signatures for each newsgroup you post to. For variety, a global signature file is still on occasion used even if a per-newsgroup file exists.</P><PCLASS="para">You can even use <EMCLASS="emphasis">sigrand</EM> on systems without named pipes if you remove the code to create a named pipe and extend the sleep interval before file updates. Then <EMCLASS="emphasis">.signature</EM> would just be a regular file. Another portability concern is that the program forks itself in the background, which is almost like becoming a <ACLASS="indexterm"NAME="ch16-idx-1000008951-0"></A>daemon. If you have no <CODECLASS="literal">fork</CODE> call, just comment it out.</P><PCLASS="para">The full program is shown in <ACLASS="xref"HREF="ch16_23.htm#ch16-36804"TITLE="sigrand">Example 16.12</A>.</P><DIVCLASS="example"><H4CLASS="example"><ACLASS="title"NAME="ch16-36804">Example 16.12: sigrand</A></H4><PRECLASS="programlisting">#!/usr/bin/perl -w# sigrand - supply random fortunes for .signature fileuse strict;# config section variablesuse vars qw( $NG_IS_DIR $MKNOD $FULLNAME $FIFO $ART $NEWS $SIGS $SEMA $GLOBRAND $NAME );# globalsuse vars qw( $Home $Fortune_Path @Pwd );################################################################# begin configuration section # should really read from ~/.sigrandrcgethome();# for rec/humor/funny instead of rec.humor.funny$NG_IS_DIR = 1; $MKNOD = "/bin/mknod";$FULLNAME = "$Home/.fullname";$FIFO = "$Home/.signature";$ART = "$Home/.article";$NEWS = "$Home/News";$SIGS = "$NEWS/SIGNATURES";$SEMA = "$Home/.sigrandpid";$GLOBRAND = 1/4; # chance to use global sigs anyway# $NAME should be (1) left undef to have program guess# read address for signature maybe looking in ~/.fullname,# (2) set to an exact address, or (3) set to empty string# to be omitted entirely.$NAME = ''; # means no name used## $NAME = "me\@home.org\n"; # end configuration section -- HOME and FORTUNE get autoconf'd################################################################setup(); # pull in initsjustme(); # make sure program not already runningfork && exit; # background ourself and go awayopen (SEMA, "> $SEMA") or die "can't write $SEMA: $!";print SEMA "$$\n";close(SEMA) or die "can't close $SEMA: $!";# now loop forever, writing a signature into the # fifo file. if you don't have real fifos, change# sleep time at bottom of loop to like 10 to update# only every 10 seconds.for (;;) { open (FIFO, "> $FIFO") or die "can't write $FIFO: $!"; my $sig = pick_quote(); for ($sig) { s/^((:?[^\n]*\n){4}).*$/$1/s; # trunc to 4 lines s/^(.{1,80}).*? *$/$1/gm; # trunc long lines } # print sig, with name if present, padded to four lines if ($NAME) { print FIFO $NAME, "\n" x (3 - ($sig =~ tr/\n//)), $sig; } else { print FIFO $sig; } close FIFO; # Without a microsleep, the reading process doesn't finish before # the writer tries to open it again, which since the reader exists, # succeeds. They end up with multiple signatures. Sleep a tiny bit # between opens to give readers a chance to finish reading and close # our pipe so we can block when opening it the next time. select(undef, undef, undef, 0.2); # sleep 1/5 second}die "XXX: NOT REACHED"; # you can't get here from anywhere################################################################# Ignore SIGPIPE in case someone opens us up and then closes the fifo# without reading it; look in a .fullname file for their login name.# Try to determine the fully qualified hostname. Look our for silly# ampersands in passwd entries. Make sure we have signatures or fortunes.# Build a fifo if we need to.sub setup { $SIG{PIPE} = 'IGNORE'; unless (defined $NAME) { # if $NAME undef in config if (-e $FULLNAME) { $NAME = `cat $FULLNAME`; die "$FULLNAME should contain only 1 line, aborting" if $NAME =~ tr/\n// > 1; } else { my($user, $host); chop($host = `hostname`); ($host) = gethostbyname($host) unless $host =~ /\./; $user = $ENV{USER} || $ENV{LOGNAME} || $Pwd[0] or die "intruder alert"; ($NAME = $Pwd[6]) =~ s/,.*//; $NAME =~ s/&/\u\L$user/g; # can't believe some folks still do this $NAME = "\t$NAME\t$user\@$host\n"; } } check_fortunes() if !-e $SIGS; unless (-p $FIFO) { # -p checks whether it's a named pipe if (!-e _) { system("$MKNOD $FIFO p") && die "can't mknod $FIFO"; warn "created $FIFO as a named pipe\n"; } else { die "$0: won't overwrite file .signature\n"; } } else { warn "$0: using existing named pipe $FIFO\n"; } # get a good random number seed. not needed if 5.004 or better. srand(time() ^ ($$ + ($$ << 15)));}# choose a random signaturesub pick_quote { my $sigfile = signame(); if (!-e $sigfile) { return fortune(); } open (SIGS, "< $sigfile" ) or die "can't open $sigfile"; local $/ = "%%\n"; local $_; my $quip; rand($.) < 1 && ($quip = $_) while <SIGS>; close SIGS; chomp $quip; return $quip || "ENOSIG: This signature file is empty.\n";} # See whether ~/.article contains a Newsgroups line. if so, see the first# group posted to and find out whether it has a dedicated set of fortunes.# otherwise return the global one. also, return the global one randomly# now and then to spice up the sigs.sub signame { (rand(1.0) > ($GLOBRAND) && open ART) || return $SIGS; local $/ = ''; local $_ = <ART>; my($ng) = /Newsgroups:\s*([^,\s]*)/; $ng =~ s!\.!/!g if $NG_IS_DIR; # if rn -/, or SAVEDIR=%p/%c $ng = "$NEWS/$ng/SIGNATURES"; return -f $ng ? $ng : $SIGS;} # Call the fortune program with -s for short flag until# we get a small enough fortune or ask too much.sub fortune { local $_; my $tries = 0; do { $_ = `$Fortune_Path -s`; } until tr/\n// < 5 || $tries++ > 20; s/^/ /mg; $_ || " SIGRAND: deliver random signals to all processes.\n";} # Make sure there's a fortune program. Search # for its full path and set global to that.sub check_fortunes { return if $Fortune_Path; # already set for my $dir (split(/:/, $ENV{PATH}), '/usr/games') { return if -x ($Fortune_Path = "$dir/fortune"); } die "Need either $SIGS or a fortune program, bailing out";} # figure out our directorysub gethome { @Pwd = getpwuid($<); $Home = $ENV{HOME} || $ENV{LOGDIR} || $Pwd[7] or die "no home directory for user $<";}# "There can be only one." --the Highlandersub justme { if (open SEMA) { my $pid; chop($pid = <SEMA>); kill(0, $pid) and die "$0 already running (pid $pid), bailing out"; close SEMA; } <ACLASS="indexterm"NAME="ch16-idx-1000006438-0"></A><ACLASS="indexterm"NAME="ch16-idx-1000006438-1"></A><ACLASS="indexterm"NAME="ch16-idx-1000006438-2"></A><ACLASS="indexterm"NAME="ch16-idx-1000006438-3"></A><ACLASS="indexterm"NAME="ch16-idx-1000006438-4"></A>} <ACLASS="indexterm"NAME="ch16-idx-1000006184-0"></A></PRE></DIV></DIV></DIV><DIVCLASS="htmlnav"><P></P><HRALIGN="LEFT"WIDTH="684"TITLE="footer"><TABLEWIDTH="684"BORDER="0"CELLSPACING="0"CELLPADDING="0"><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="228"><ACLASS="sect1"HREF="ch16_22.htm"TITLE="16.21. Timing Out an Operation"><IMGSRC="../gifs/txtpreva.gif"ALT="Previous: 16.21. Timing Out an Operation"BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="228"><ACLASS="book"HREF="index.htm"TITLE="Perl Cookbook"><IMGSRC="../gifs/txthome.gif"ALT="Perl Cookbook"BORDER="0"></A></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="228"><ACLASS="chapter"HREF="ch17_01.htm"TITLE="17. Sockets"><IMGSRC="../gifs/txtnexta.gif"ALT="Next: 17. Sockets"BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="228">16.21. Timing Out an Operation</TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="228"><ACLASS="index"HREF="index/index.htm"TITLE="Book Index"><IMGSRC="../gifs/index.gif"ALT="Book Index"BORDER="0"></A></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="228">17. Sockets</TD></TR></TABLE><HRALIGN="LEFT"WIDTH="684"TITLE="footer"><FONTSIZE="-1"></DIV<!-- LIBRARY NAV BAR --> <img src="../gifs/smnavbar.gif" usemap="#library-map" border="0" alt="Library Navigation Links"><p> <a href="copyrght.htm">Copyright © 2002</a> O'Reilly & Associates. All rights reserved.</font> </p> <map name="library-map"> <area shape="rect" coords="1,0,85,94" href="../index.htm"><area shape="rect" coords="86,1,178,103" href="../lwp/index.htm"><area shape="rect" coords="180,0,265,103" href="../lperl/index.htm"><area shape="rect" coords="267,0,353,105" href="../perlnut/index.htm"><area shape="rect" coords="354,1,446,115" href="../prog/index.htm"><area shape="rect" coords="448,0,526,132" href="../tk/index.htm"><area shape="rect" coords="528,1,615,119" href="../cookbook/index.htm"><area shape="rect" coords="617,0,690,135" href="../pxml/index.htm"></map> </BODY></HTML>⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -