欢迎各位兄弟 发布技术文章
这里的技术是共享的
Ralf S. Engelschall <rse@apache.org>
mod_rewrite参考文档mod_rewrite
mod_rewritemod_rewritemod_rewrite
mod_rewrite
[PT]对_别名 mod_userdirhtaccess /~user/u/user
RewriteRule ^/~([^/]+)/?(.*) /u/$1/$2 [R] RewriteRule ^/([uge])/([^/]+)$ /$1/$2/ [R]
# For sites running on a port other than 80
RewriteCond %{HTTP_HOST}   !^www\.example\.com [NC]
RewriteCond %{HTTP_HOST}   !^$
RewriteCond %{SERVER_PORT} !^80$
RewriteRule ^/(.*)         http://www.example.com:%{SERVER_PORT}/$1 [L,R]
# And for a site running on port 80
RewriteCond %{HTTP_HOST}   !^www\.example\.com [NC]
RewriteCond %{HTTP_HOST}   !^$
RewriteRule ^/(.*)         http://www.example.com/$1 [L,R]
DocumentRootDocumentRoot/e/www/DocumentRoot
/
RewriteEngine on RewriteRule ^/$ /e/www/ [R]
RedirectMatch
RedirectMatch ^/$ http://example.com/e/www/
/~quux/foofoo
image.gif/~quux/image.gif
RewriteEngine on RewriteBase /~quux/ RewriteRule ^foo$ foo/ [R]
.htaccess
RewriteEngine  on
RewriteBase    /~quux/
RewriteCond    %{REQUEST_FILENAME}  -d
RewriteRule    ^(.+[^/])$           $1/  [R]
user1 server_of_user1 user2 server_of_user2 : :
map.xxx-to-host
/u/user/anypath /g/group/anypath /e/entity/anypath
http://physical-host/u/user/anypath http://physical-host/g/group/anypath http://physical-host/e/entity/anypath
RewriteEngine on
RewriteMap      user-to-host   txt:/path/to/map.user-to-host
RewriteMap     group-to-host   txt:/path/to/map.group-to-host
RewriteMap    entity-to-host   txt:/path/to/map.entity-to-host
RewriteRule   ^/u/([^/]+)/?(.*)   http://${user-to-host:$1|server0}/u/$1/$2
RewriteRule   ^/g/([^/]+)/?(.*)  http://${group-to-host:$1|server0}/g/$1/$2
RewriteRule   ^/e/([^/]+)/?(.*) http://${entity-to-host:$1|server0}/e/$1/$2
RewriteRule   ^/([uge])/([^/]+)/?$          /$1/$2/.www/
RewriteRule   ^/([uge])/([^/]+)/([^.]+.+)   /$1/$2/.www/$3\
mod_rewritehttp://newserver/~user/anypath
RewriteEngine on RewriteRule ^/~(.+) http://newserver/~$1 [R,L]
/~foo/anypath/~bar/anypath
RewriteEngine on RewriteRule ^/~(([a-z])[a-z0-9]+)(.*) /home/$2/$1/.www$3
RewriteRules
drwxrwxr-x 2 netsw users 512 Aug 3 18:39 Audio/ drwxrwxr-x 2 netsw users 512 Jul 9 14:37 Benchmark/ drwxrwxr-x 12 netsw users 512 Jul 9 00:34 Crypto/ drwxrwxr-x 5 netsw users 512 Jul 9 00:41 Database/ drwxrwxr-x 4 netsw users 512 Jul 30 19:25 Dicts/ drwxrwxr-x 10 netsw users 512 Jul 9 01:54 Graphic/ drwxrwxr-x 5 netsw users 512 Jul 9 01:58 Hackers/ drwxrwxr-x 8 netsw users 512 Jul 9 03:19 InfoSys/ drwxrwxr-x 3 netsw users 512 Jul 9 03:21 Math/ drwxrwxr-x 3 netsw users 512 Jul 9 03:24 Misc/ drwxrwxr-x 9 netsw users 512 Aug 1 16:33 Network/ drwxrwxr-x 2 netsw users 512 Jul 9 05:53 Office/ drwxrwxr-x 7 netsw users 512 Jul 9 09:24 SoftEng/ drwxrwxr-x 7 netsw users 512 Jul 9 12:17 System/ drwxrwxr-x 12 netsw users 512 Aug 3 20:15 Typesetting/ drwxrwxr-x 10 netsw users 512 Jul 9 14:08 X11/
/e/netsw/.www/
-rw-r--r-- 1 netsw users 1318 Aug 1 18:10 .wwwacl drwxr-xr-x 18 netsw users 512 Aug 5 15:51 DATA/ -rw-rw-rw- 1 netsw users 372982 Aug 5 16:35 LOGFILE -rw-r--r-- 1 netsw users 659 Aug 4 09:27 TODO -rw-r--r-- 1 netsw users 5697 Aug 1 18:01 netsw-about.html -rwxr-xr-x 1 netsw users 579 Aug 2 10:33 netsw-access.pl -rwxr-xr-x 1 netsw users 1532 Aug 1 17:35 netsw-changes.cgi -rwxr-xr-x 1 netsw users 2866 Aug 5 14:49 netsw-home.cgi drwxr-xr-x 2 netsw users 512 Jul 8 23:47 netsw-img/ -rwxr-xr-x 1 netsw users 24050 Aug 5 15:49 netsw-lsdir.cgi -rwxr-xr-x 1 netsw users 1589 Aug 3 18:43 netsw-search.cgi -rwxr-xr-x 1 netsw users 1885 Aug 1 17:41 netsw-tree.cgi -rw-r--r-- 1 netsw users 234 Jul 30 16:35 netsw-unlimit.lst
DATA/rdistDocumentRoot/e/netsw
RewriteRule ^net.sw$ net.sw/ [R] RewriteRule ^net.sw/(.*)$ e/netsw/$1
/e/netsw/.www/.wwwacl
Options ExecCGI FollowSymLinks Includes MultiViews RewriteEngine on # we are reached via /net.sw/ prefix RewriteBase /net.sw/ # first we rewrite the root dir to # the handling cgi script RewriteRule ^$ netsw-home.cgi [L] RewriteRule ^index\.html$ netsw-home.cgi [L] # strip out the subdirs when # the browser requests us from perdir pages RewriteRule ^.+/(netsw-[^/]+/.+)$ $1 [L] # and now break the rewriting for local files RewriteRule ^netsw-home\.cgi.* - [L] RewriteRule ^netsw-changes\.cgi.* - [L] RewriteRule ^netsw-search\.cgi.* - [L] RewriteRule ^netsw-tree\.cgi$ - [L] RewriteRule ^netsw-about\.html$ - [L] RewriteRule ^netsw-img/.*$ - [L] # anything else is a subdir which gets handled # by another cgi script RewriteRule !^netsw-lsdir\.cgi.* - [C] RewriteRule (.*) netsw-lsdir.cgi/$1
L— !C mod_imapimagemapimagemap/path/to/page.map
RewriteEngine on RewriteRule ^/cgi-bin/imagemap(.*) $1 [PT]
RewriteEngine on
#   first try to find it in custom/...
#   ...and if found stop and be happy:
RewriteCond         /your/docroot/dir1/%{REQUEST_FILENAME}  -f
RewriteRule  ^(.+)  /your/docroot/dir1/$1  [L]
#   second try to find it in pub/...
#   ...and if found stop and be happy:
RewriteCond         /your/docroot/dir2/%{REQUEST_FILENAME}  -f
RewriteRule  ^(.+)  /your/docroot/dir2/$1  [L]
#   else go on for other Alias or ScriptAlias directives,
#   etc.
RewriteRule   ^(.+)  -  [PT]
/foo/S=java/bar/STATUS
RewriteEngine on RewriteRule ^(.*)/S=([^/]+)/(.*) $1/$3 [E=STATUS:$2]
www.username.host.domain.com
http://www.username.host.com/anypath
RewriteEngine on
RewriteCond   %{HTTP_HOST}                 ^www\.[^.]+\.host\.com$
RewriteRule   ^(.+)                        %{HTTP_HOST}$1          [C]
RewriteRule   ^www\.([^.]+)\.host\.com(.*) /home/$1$2
www.somewhere.com
RewriteEngine on
RewriteCond   %{REMOTE_HOST}  !^.+\.ourdomain\.com$
RewriteRule   ^(/~.+)         http://www.somewhere.com/$1 [R,L]
ErrorDocumentErrorDocument
RewriteEngine on
RewriteCond   /your/docroot/%{REQUEST_FILENAME} !-f
RewriteRule   ^(.+)                             http://webserverB.dom/$1
DocumentRoot
RewriteEngine on
RewriteCond   %{REQUEST_URI} !-U
RewriteRule   ^(.+)          http://webserverB.dom/$1
mod_rewrite
url#anchoruri_escape()
We have to use a kludge by the use of a NPH-CGI script which does the redirect itself. Because here no escaping is done (NPH=non-parseable headers). First we introduce a new URL schemexredirect:
RewriteRule ^xredirect:(.+) /path/to/nph-xredirect.cgi/$1 \
            [T=application/x-httpd-cgi,L]
xredirect:
#!/path/to/perl
##
##  nph-xredirect.cgi -- NPH/CGI script for extended redirects
##  Copyright (c) 1997 Ralf S. Engelschall, All Rights Reserved.
##
$| = 1;
$url = $ENV{'PATH_INFO'};
print "HTTP/1.0 302 Moved Temporarily\n";
print "Server: $ENV{'SERVER_SOFTWARE'}\n";
print "Location: $url\n";
print "Content-type: text/html\n";
print "\n";
print "<html>\n";
print "<head>\n";
print "<title>302 Moved Temporarily (EXTENDED)</title>\n";
print "</head>\n";
print "<body>\n";
print "<h1>Moved Temporarily (EXTENDED)</h1>\n";
print "The document has moved <a HREF=\"$url\">here</a>.<p>\n";
print "</body>\n";
print "</html>\n";
##EOF##
mod_rewrite
RewriteRule ^anyurl xredirect:news:newsgroup
[R][ R ] xredirect:mod_rewrite
mod_rewriteRewriteMap
RewriteEngine on
RewriteMap    multiplex                txt:/path/to/map.cxan
RewriteRule   ^/CxAN/(.*)              %{REMOTE_HOST}::$1                 [C]
RewriteRule   ^.+\.([a-zA-Z]+)::(.*)$  ${multiplex:$1|ftp.default.dom}$2  [R,L]
## ## map.cxan -- Multiplexing Map for CxAN ## de ftp://ftp.cxan.de/CxAN/ uk ftp://ftp.cxan.uk/CxAN/ com ftp://ftp.cxan.com/CxAN/ : ##EOF##
mod_rewrite
TIME_xxx<STRING>STRING=STRING
RewriteEngine on
RewriteCond   %{TIME_HOUR}%{TIME_MIN} >0700
RewriteCond   %{TIME_HOUR}%{TIME_MIN} <1900
RewriteRule   ^foo\.html$             foo.day.html
RewriteRule   ^foo\.html$             foo.night.html
foo.day.html07:00-19:00
document.YYYY.html
#   backward compatibility ruleset for
#   rewriting document.html to document.phtml
#   when and only when document.phtml exists
#   but no longer document.html
RewriteEngine on
RewriteBase   /~quux/
#   parse out basename, but remember the fact
RewriteRule   ^(.*)\.html$              $1      [C,E=WasHTML:yes]
#   rewrite to document.phtml if exists
RewriteCond   %{REQUEST_FILENAME}.phtml -f
RewriteRule   ^(.*)$ $1.phtml                   [S=1]
#   else reverse the previous basename cutout
RewriteCond   %{ENV:WasHTML}            ^yes$
RewriteRule   ^(.*)$ $1.html
foo.html
RewriteEngine on RewriteBase /~quux/ RewriteRule ^foo\.html$ bar.html
foo.html
RewriteEngine on RewriteBase /~quux/ RewriteRule ^foo\.html$ bar.html [R]
foo.htmlfoo.20.html
RewriteCond %{HTTP_USER_AGENT}  ^Mozilla/3.*
RewriteRule ^foo\.html$         foo.NS.html          [L]
RewriteCond %{HTTP_USER_AGENT}  ^Lynx/.*         [OR]
RewriteCond %{HTTP_USER_AGENT}  ^Mozilla/[12].*
RewriteRule ^foo\.html$         foo.20.html          [L]
RewriteRule ^foo\.html$         foo.32.html          [L]
mirror
[P]
RewriteEngine on RewriteBase /~quux/ RewriteRule ^hotsheet/(.*)$ http://www.tstimpreso.com/hotsheet/$1 [P]
RewriteEngine on RewriteBase /~quux/ RewriteRule ^usa-news\.html$ http://www.quux-corp.com/news/index.html [P]
RewriteEngine on RewriteCond /mirror/of/remotesite/$1 -U RewriteRule ^http://www\.remotesite\.com/(.*)$ /mirror/of/remotesite/$1
www.quux-corp.dom
ALLOW Host www.quux-corp.dom Port >1024 --> Host www2.quux-corp.dom Port 80 DENY Host * Port * --> Host www2.quux-corp.dom Port 80
mod_rewrite
RewriteRule ^/~([^/]+)/?(.*)          /home/$1/.www/$2
RewriteCond %{REQUEST_FILENAME}       !-f
RewriteCond %{REQUEST_FILENAME}       !-d
RewriteRule ^/home/([^/]+)/.www/?(.*) http://www2.quux-corp.dom/~$1/pub/$2 [P]
www.foo.com
mod_rewrite
BIND
www0 IN A 1.2.3.1 www1 IN A 1.2.3.2 www2 IN A 1.2.3.3 www3 IN A 1.2.3.4 www4 IN A 1.2.3.5 www5 IN A 1.2.3.6
www    IN  CNAME   www0.foo.com.
       IN  CNAME   www1.foo.com.
       IN  CNAME   www2.foo.com.
       IN  CNAME   www3.foo.com.
       IN  CNAME   www4.foo.com.
       IN  CNAME   www5.foo.com.
       IN  CNAME   www6.foo.com.
BINDBINDwww.foo.comwwwN.foo.com
lbnamed
mod_rewritewww.foo.com
www IN CNAME www0.foo.com.
www0.foo.comlb.pl
RewriteEngine on
RewriteMap    lb      prg:/path/to/lb.pl
RewriteRule   ^/(.+)$ ${lb:$1}           [P,L]
lb.pl
#!/path/to/perl
##
##  lb.pl -- load balancing script
##
$| = 1;
$name   = "www";     # the hostname base
$first  = 1;         # the first server (not 0 here, because 0 is myself)
$last   = 5;         # the last server in the round-robin
$domain = "foo.dom"; # the domainname
$cnt = 0;
while (<STDIN>) {
    $cnt = (($cnt+1) % ($last+1-$first));
    $server = sprintf("%s%d.%s", $name, $cnt+$first, $domain);
    print "http://$server/$_";
}
##EOF##
www0.foo.comPATH_INFO.scgi/u/user/foo/bar.scgi/~user/foo/bar.scgi/
RewriteRule ^/[uge]/([^/]+)/\.www/(.+)\.scgi(.*) ... ... /internal/cgi/user/cgiwrap/~$1/$2.scgi$3 [NS,T=application/x-http-cgi]
wwwlogwwwidx/u/user/foo/
/internal/cgi/user/swwidx?i=/u/user/foo/
RewriteRule ^/([uge])/([^/]+)(/?.*)/\* /internal/cgi/user/wwwidx?i=/$1/$2$3/ RewriteRule ^/([uge])/([^/]+)(/?.*):log /internal/cgi/user/wwwlog?f=/$1/$2$3
/u/user/foo/
HREF="*"
/internal/cgi/user/wwwidx?i=/u/user/foo/
:log
foo.html
/~quux/foo.html
RewriteEngine on RewriteBase /~quux/ RewriteRule ^foo\.html$ foo.cgi [T=application/x-httpd-cgi]
RewriteCond %{REQUEST_FILENAME}   !-s
RewriteRule ^page\.html$          page.cgi   [T=application/x-httpd-cgi,L]
page.htmlpage.htmlSTDOUTpage.html
mod_rewrite
RewriteRule ^(/[uge]/[^/]+/?.*):refresh /internal/cgi/apache/nph-refresh?f=$1
/u/foo/bar/page.html:refresh
/internal/cgi/apache/nph-refresh?f=/u/foo/bar/page.html
#!/sw/bin/perl
##
##  nph-refresh -- NPH/CGI script for auto refreshing pages
##  Copyright (c) 1997 Ralf S. Engelschall, All Rights Reserved.
##
$| = 1;
#   split the QUERY_STRING variable
@pairs = split(/&/, $ENV{'QUERY_STRING'});
foreach $pair (@pairs) {
    ($name, $value) = split(/=/, $pair);
    $name =~ tr/A-Z/a-z/;
    $name = 'QS_' . $name;
    $value =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C", hex($1))/eg;
    eval "\$$name = \"$value\"";
}
$QS_s = 1 if ($QS_s eq '');
$QS_n = 3600 if ($QS_n eq '');
if ($QS_f eq '') {
    print "HTTP/1.0 200 OK\n";
    print "Content-type: text/html\n\n";
    print "<b>ERROR</b>: No file given\n";
    exit(0);
}
if (! -f $QS_f) {
    print "HTTP/1.0 200 OK\n";
    print "Content-type: text/html\n\n";
    print "<b>ERROR</b>: File $QS_f not found\n";
    exit(0);
}
sub print_http_headers_multipart_begin {
    print "HTTP/1.0 200 OK\n";
    $bound = "ThisRandomString12345";
    print "Content-type: multipart/x-mixed-replace;boundary=$bound\n";
    &print_http_headers_multipart_next;
}
sub print_http_headers_multipart_next {
    print "\n--$bound\n";
}
sub print_http_headers_multipart_end {
    print "\n--$bound--\n";
}
sub displayhtml {
    local($buffer) = @_;
    $len = length($buffer);
    print "Content-type: text/html\n";
    print "Content-length: $len\n\n";
    print $buffer;
}
sub readfile {
    local($file) = @_;
    local(*FP, $size, $buffer, $bytes);
    ($x, $x, $x, $x, $x, $x, $x, $size) = stat($file);
    $size = sprintf("%d", $size);
    open(FP, "<$file");
    $bytes = sysread(FP, $buffer, $size);
    close(FP);
    return $buffer;
}
$buffer = &readfile($QS_f);
&print_http_headers_multipart_begin;
&displayhtml($buffer);
sub mystat {
    local($file) = $_[0];
    local($time);
    ($x, $x, $x, $x, $x, $x, $x, $x, $x, $mtime) = stat($file);
    return $mtime;
}
$mtimeL = &mystat($QS_f);
$mtime = $mtime;
for ($n = 0; $n < $QS_n; $n++) {
    while (1) {
        $mtime = &mystat($QS_f);
        if ($mtime ne $mtimeL) {
            $mtimeL = $mtime;
            sleep(2);
            $buffer = &readfile($QS_f);
            &print_http_headers_multipart_next;
            &displayhtml($buffer);
            sleep(5);
            $mtimeL = &mystat($QS_f);
            last;
        }
        sleep($QS_s);
    }
}
&print_http_headers_multipart_end;
exit(0);
##EOF##
<VirtualHost>
[P]
##
##  vhost.map
##
www.vhost1.dom:80  /path/to/docroot/vhost1
www.vhost2.dom:80  /path/to/docroot/vhost2
     :
www.vhostN.dom:80  /path/to/docroot/vhostN
##
##  httpd.conf
##
    :
#   use the canonical hostname on redirects, etc.
UseCanonicalName on
    :
#   add the virtual host in front of the CLF-format
CustomLog  /path/to/access_log  "%{VHOST}e %h %l %u %t \"%r\" %>s %b"
    :
#   enable the rewriting engine in the main server
RewriteEngine on
#   define two maps: one for fixing the URL and one which defines
#   the available virtual hosts with their corresponding
#   DocumentRoot.
RewriteMap    lowercase    int:tolower
RewriteMap    vhost        txt:/path/to/vhost.map
#   Now do the actual virtual host mapping
#   via a huge and complicated single rule:
#
#   1. make sure we don't map for common locations
RewriteCond   %{REQUEST_URI}  !^/commonurl1/.*
RewriteCond   %{REQUEST_URI}  !^/commonurl2/.*
    :
RewriteCond   %{REQUEST_URI}  !^/commonurlN/.*
#
#   2. make sure we have a Host header, because
#      currently our approach only supports
#      virtual hosting through this header
RewriteCond   %{HTTP_HOST}  !^$
#
#   3. lowercase the hostname
RewriteCond   ${lowercase:%{HTTP_HOST}|NONE}  ^(.+)$
#
#   4. lookup this hostname in vhost.map and
#      remember it only when it is a path
#      (and not "NONE" from above)
RewriteCond   ${vhost:%1}  ^(/.*)$
#
#   5. finally we can map the URL to its docroot location
#      and remember the virtual host for logging puposes
RewriteRule   ^/(.*)$   %1/$1  [E=VHOST:${lowercase:%{HTTP_HOST}}]
    :
/robots.txt
/~quux/foo/arc/
RewriteCond %{HTTP_USER_AGENT}   ^NameOfBadRobot.*
RewriteCond %{REMOTE_ADDR}       ^123\.45\.67\.[8-9]$
RewriteRule ^/~quux/foo/arc/.+   -   [F]
http://www.quux-corp.de/~quux/
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http://www.quux-corp.de/~quux/.*$ [NC]
RewriteRule .*\.gif$        -                                    [F]
RewriteCond %{HTTP_REFERER}         !^$
RewriteCond %{HTTP_REFERER}         !.*/foo-with-gif\.html$
RewriteRule ^inlined-in-foo\.gif$   -                        [F]
For Apache >= 1.3b6:
RewriteEngine on
RewriteMap    hosts-deny  txt:/path/to/hosts.deny
RewriteCond   ${hosts-deny:%{REMOTE_HOST}|NOT-FOUND} !=NOT-FOUND [OR]
RewriteCond   ${hosts-deny:%{REMOTE_ADDR}|NOT-FOUND} !=NOT-FOUND
RewriteRule   ^/.*  -  [F]
For Apache <= 1.3b6:
RewriteEngine on
RewriteMap    hosts-deny  txt:/path/to/hosts.deny
RewriteRule   ^/(.*)$ ${hosts-deny:%{REMOTE_HOST}|NOT-FOUND}/$1
RewriteRule   !^NOT-FOUND/.* - [F]
RewriteRule   ^NOT-FOUND/(.*)$ ${hosts-deny:%{REMOTE_ADDR}|NOT-FOUND}/$1
RewriteRule   !^NOT-FOUND/.* - [F]
RewriteRule   ^NOT-FOUND/(.*)$ /$1
## ## hosts.deny ## ## ATTENTION! This is a map, not a list, even when we treat it as such. ## mod_rewrite parses it for key/value pairs, so at least a ## dummy value "-" must be present for each entry. ## 193.102.180.41 - bsdti1.sdm.de - 192.76.162.40 -
mod_rewritemod_proxy
RewriteCond %{REMOTE_HOST} ^badhost\.mydomain\.com$
RewriteRule !^http://[^/.]\.mydomain.com.*  - [F]
RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST}  ^badguy@badhost\.mydomain\.com$
RewriteRule !^http://[^/.]\.mydomain.com.*  - [F]
mod_auth
RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} !^friend1@client1.quux-corp\.com$
RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} !^friend2@client2.quux-corp\.com$
RewriteCond %{REMOTE_IDENT}@%{REMOTE_HOST} !^friend3@client3.quux-corp\.com$
RewriteRule ^/~quux/only-for-friends/      -                                 [F]
RewriteMap  deflector txt:/path/to/deflector.map
RewriteCond %{HTTP_REFERER} !=""
RewriteCond ${deflector:%{HTTP_REFERER}} ^-$
RewriteRule ^.* %{HTTP_REFERER} [R,L]
RewriteCond %{HTTP_REFERER} !=""
RewriteCond ${deflector:%{HTTP_REFERER}|NOT-FOUND} !=NOT-FOUND
RewriteRule ^.* ${deflector:%{HTTP_REFERER}} [R,L]
## ## deflector.map ## http://www.badguys.com/bad/index.html - http://www.badguys.com/bad/index2.html - http://www.badguys.com/bad/index3.html http://somewhere.com/
-
mod_rewrite
RewriteMapSTDIN
RewriteEngine on
RewriteMap    quux-map       prg:/path/to/map.quux.pl
RewriteRule   ^/~quux/(.*)$  /~quux/${quux-map:$1}
#!/path/to/perl
#   disable buffered I/O which would lead
#   to deadloops for the Apache server
$| = 1;
#   read URLs one per line from stdin and
#   generate substitution URL on stdout
while (<>) {
    s|^foo/|bar/|;
    print $_;
}
/~quux/foo/...