1 | =head1 NAME
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2 |
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3 | perlfaq9 - Networking ($Revision: 1.28 $, $Date: 2005/12/31 00:54:37 $)
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4 |
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5 | =head1 DESCRIPTION
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6 |
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7 | This section deals with questions related to networking, the internet,
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8 | and a few on the web.
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9 |
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10 | =head2 What is the correct form of response from a CGI script?
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11 |
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12 | (Alan Flavell <[email protected]> answers...)
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13 |
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14 | The Common Gateway Interface (CGI) specifies a software interface between
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15 | a program ("CGI script") and a web server (HTTPD). It is not specific
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16 | to Perl, and has its own FAQs and tutorials, and usenet group,
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17 | comp.infosystems.www.authoring.cgi
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18 |
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19 | The CGI specification is outlined in an informational RFC:
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20 | http://www.ietf.org/rfc/rfc3875
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21 |
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22 | Other relevant documentation listed in: http://www.perl.org/CGI_MetaFAQ.html
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23 |
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24 | These Perl FAQs very selectively cover some CGI issues. However, Perl
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25 | programmers are strongly advised to use the CGI.pm module, to take care
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26 | of the details for them.
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27 |
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28 | The similarity between CGI response headers (defined in the CGI
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29 | specification) and HTTP response headers (defined in the HTTP
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30 | specification, RFC2616) is intentional, but can sometimes be confusing.
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31 |
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32 | The CGI specification defines two kinds of script: the "Parsed Header"
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33 | script, and the "Non Parsed Header" (NPH) script. Check your server
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34 | documentation to see what it supports. "Parsed Header" scripts are
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35 | simpler in various respects. The CGI specification allows any of the
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36 | usual newline representations in the CGI response (it's the server's
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37 | job to create an accurate HTTP response based on it). So "\n" written in
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38 | text mode is technically correct, and recommended. NPH scripts are more
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39 | tricky: they must put out a complete and accurate set of HTTP
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40 | transaction response headers; the HTTP specification calls for records
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41 | to be terminated with carriage-return and line-feed, i.e ASCII \015\012
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42 | written in binary mode.
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43 |
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44 | Using CGI.pm gives excellent platform independence, including EBCDIC
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45 | systems. CGI.pm selects an appropriate newline representation
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46 | ($CGI::CRLF) and sets binmode as appropriate.
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47 |
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48 | =head2 My CGI script runs from the command line but not the browser. (500 Server Error)
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49 |
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50 | Several things could be wrong. You can go through the "Troubleshooting
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51 | Perl CGI scripts" guide at
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52 |
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53 | http://www.perl.org/troubleshooting_CGI.html
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54 |
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55 | If, after that, you can demonstrate that you've read the FAQs and that
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56 | your problem isn't something simple that can be easily answered, you'll
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57 | probably receive a courteous and useful reply to your question if you
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58 | post it on comp.infosystems.www.authoring.cgi (if it's something to do
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59 | with HTTP or the CGI protocols). Questions that appear to be Perl
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60 | questions but are really CGI ones that are posted to comp.lang.perl.misc
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61 | are not so well received.
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62 |
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63 | The useful FAQs, related documents, and troubleshooting guides are
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64 | listed in the CGI Meta FAQ:
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65 |
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66 | http://www.perl.org/CGI_MetaFAQ.html
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67 |
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68 |
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69 | =head2 How can I get better error messages from a CGI program?
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70 |
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71 | Use the CGI::Carp module. It replaces C<warn> and C<die>, plus the
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72 | normal Carp modules C<carp>, C<croak>, and C<confess> functions with
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73 | more verbose and safer versions. It still sends them to the normal
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74 | server error log.
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75 |
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76 | use CGI::Carp;
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77 | warn "This is a complaint";
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78 | die "But this one is serious";
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79 |
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80 | The following use of CGI::Carp also redirects errors to a file of your choice,
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81 | placed in a BEGIN block to catch compile-time warnings as well:
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82 |
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83 | BEGIN {
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84 | use CGI::Carp qw(carpout);
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85 | open(LOG, ">>/var/local/cgi-logs/mycgi-log")
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86 | or die "Unable to append to mycgi-log: $!\n";
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87 | carpout(*LOG);
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88 | }
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89 |
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90 | You can even arrange for fatal errors to go back to the client browser,
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91 | which is nice for your own debugging, but might confuse the end user.
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92 |
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93 | use CGI::Carp qw(fatalsToBrowser);
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94 | die "Bad error here";
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95 |
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96 | Even if the error happens before you get the HTTP header out, the module
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97 | will try to take care of this to avoid the dreaded server 500 errors.
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98 | Normal warnings still go out to the server error log (or wherever
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99 | you've sent them with C<carpout>) with the application name and date
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100 | stamp prepended.
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101 |
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102 | =head2 How do I remove HTML from a string?
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103 |
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104 | The most correct way (albeit not the fastest) is to use HTML::Parser
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105 | from CPAN. Another mostly correct
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106 | way is to use HTML::FormatText which not only removes HTML but also
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107 | attempts to do a little simple formatting of the resulting plain text.
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108 |
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109 | Many folks attempt a simple-minded regular expression approach, like
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110 | C<< s/<.*?>//g >>, but that fails in many cases because the tags
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111 | may continue over line breaks, they may contain quoted angle-brackets,
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112 | or HTML comment may be present. Plus, folks forget to convert
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113 | entities--like C<<> for example.
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114 |
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115 | Here's one "simple-minded" approach, that works for most files:
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116 |
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117 | #!/usr/bin/perl -p0777
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118 | s/<(?:[^>'"]*|(['"]).*?\1)*>//gs
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119 |
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120 | If you want a more complete solution, see the 3-stage striphtml
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121 | program in
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122 | http://www.cpan.org/authors/Tom_Christiansen/scripts/striphtml.gz
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123 | .
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124 |
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125 | Here are some tricky cases that you should think about when picking
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126 | a solution:
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127 |
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128 | <IMG SRC = "foo.gif" ALT = "A > B">
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129 |
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130 | <IMG SRC = "foo.gif"
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131 | ALT = "A > B">
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132 |
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133 | <!-- <A comment> -->
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134 |
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135 | <script>if (a<b && a>c)</script>
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136 |
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137 | <# Just data #>
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138 |
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139 | <![INCLUDE CDATA [ >>>>>>>>>>>> ]]>
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140 |
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141 | If HTML comments include other tags, those solutions would also break
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142 | on text like this:
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143 |
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144 | <!-- This section commented out.
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145 | <B>You can't see me!</B>
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146 | -->
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147 |
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148 | =head2 How do I extract URLs?
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149 |
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150 | You can easily extract all sorts of URLs from HTML with
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151 | C<HTML::SimpleLinkExtor> which handles anchors, images, objects,
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152 | frames, and many other tags that can contain a URL. If you need
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153 | anything more complex, you can create your own subclass of
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154 | C<HTML::LinkExtor> or C<HTML::Parser>. You might even use
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155 | C<HTML::SimpleLinkExtor> as an example for something specifically
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156 | suited to your needs.
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157 |
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158 | You can use URI::Find to extract URLs from an arbitrary text document.
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159 |
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160 | Less complete solutions involving regular expressions can save
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161 | you a lot of processing time if you know that the input is simple. One
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162 | solution from Tom Christiansen runs 100 times faster than most
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163 | module based approaches but only extracts URLs from anchors where the first
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164 | attribute is HREF and there are no other attributes.
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165 |
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166 | #!/usr/bin/perl -n00
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167 | # qxurl - [email protected]
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168 | print "$2\n" while m{
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169 | < \s*
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170 | A \s+ HREF \s* = \s* (["']) (.*?) \1
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171 | \s* >
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172 | }gsix;
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173 |
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174 |
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175 | =head2 How do I download a file from the user's machine? How do I open a file on another machine?
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176 |
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177 | In this case, download means to use the file upload feature of HTML
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178 | forms. You allow the web surfer to specify a file to send to your web
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179 | server. To you it looks like a download, and to the user it looks
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180 | like an upload. No matter what you call it, you do it with what's
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181 | known as B<multipart/form-data> encoding. The CGI.pm module (which
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182 | comes with Perl as part of the Standard Library) supports this in the
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183 | start_multipart_form() method, which isn't the same as the startform()
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184 | method.
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185 |
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186 | See the section in the CGI.pm documentation on file uploads for code
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187 | examples and details.
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188 |
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189 | =head2 How do I make a pop-up menu in HTML?
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190 |
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191 | Use the B<< <SELECT> >> and B<< <OPTION> >> tags. The CGI.pm
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192 | module (available from CPAN) supports this widget, as well as many
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193 | others, including some that it cleverly synthesizes on its own.
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194 |
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195 | =head2 How do I fetch an HTML file?
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196 |
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197 | One approach, if you have the lynx text-based HTML browser installed
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198 | on your system, is this:
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199 |
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200 | $html_code = `lynx -source $url`;
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201 | $text_data = `lynx -dump $url`;
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202 |
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203 | The libwww-perl (LWP) modules from CPAN provide a more powerful way
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204 | to do this. They don't require lynx, but like lynx, can still work
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205 | through proxies:
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206 |
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207 | # simplest version
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208 | use LWP::Simple;
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209 | $content = get($URL);
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210 |
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211 | # or print HTML from a URL
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212 | use LWP::Simple;
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213 | getprint "http://www.linpro.no/lwp/";
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214 |
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215 | # or print ASCII from HTML from a URL
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216 | # also need HTML-Tree package from CPAN
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217 | use LWP::Simple;
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218 | use HTML::Parser;
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219 | use HTML::FormatText;
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220 | my ($html, $ascii);
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221 | $html = get("http://www.perl.com/");
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222 | defined $html
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223 | or die "Can't fetch HTML from http://www.perl.com/";
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224 | $ascii = HTML::FormatText->new->format(parse_html($html));
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225 | print $ascii;
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226 |
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227 | =head2 How do I automate an HTML form submission?
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228 |
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229 | If you are doing something complex, such as moving through many pages
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230 | and forms or a web site, you can use C<WWW::Mechanize>. See its
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231 | documentation for all the details.
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232 |
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233 | If you're submitting values using the GET method, create a URL and encode
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234 | the form using the C<query_form> method:
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235 |
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236 | use LWP::Simple;
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237 | use URI::URL;
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238 |
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239 | my $url = url('http://www.perl.com/cgi-bin/cpan_mod');
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240 | $url->query_form(module => 'DB_File', readme => 1);
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241 | $content = get($url);
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242 |
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243 | If you're using the POST method, create your own user agent and encode
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244 | the content appropriately.
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245 |
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246 | use HTTP::Request::Common qw(POST);
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247 | use LWP::UserAgent;
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248 |
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249 | $ua = LWP::UserAgent->new();
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250 | my $req = POST 'http://www.perl.com/cgi-bin/cpan_mod',
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251 | [ module => 'DB_File', readme => 1 ];
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252 | $content = $ua->request($req)->as_string;
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253 |
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254 | =head2 How do I decode or create those %-encodings on the web?
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255 |
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256 | If you are writing a CGI script, you should be using the CGI.pm module
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257 | that comes with perl, or some other equivalent module. The CGI module
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258 | automatically decodes queries for you, and provides an escape()
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259 | function to handle encoding.
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260 |
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261 | The best source of detailed information on URI encoding is RFC 2396.
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262 | Basically, the following substitutions do it:
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263 |
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264 | s/([^\w()'*~!.-])/sprintf '%%%02x', ord $1/eg; # encode
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265 |
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266 | s/%([A-Fa-f\d]{2})/chr hex $1/eg; # decode
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267 | s/%([[:xdigit:]]{2})/chr hex $1/eg; # same thing
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268 |
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269 | However, you should only apply them to individual URI components, not
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270 | the entire URI, otherwise you'll lose information and generally mess
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271 | things up. If that didn't explain it, don't worry. Just go read
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272 | section 2 of the RFC, it's probably the best explanation there is.
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273 |
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274 | RFC 2396 also contains a lot of other useful information, including a
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275 | regexp for breaking any arbitrary URI into components (Appendix B).
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276 |
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277 | =head2 How do I redirect to another page?
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278 |
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279 | Specify the complete URL of the destination (even if it is on the same
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280 | server). This is one of the two different kinds of CGI "Location:"
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281 | responses which are defined in the CGI specification for a Parsed Headers
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282 | script. The other kind (an absolute URLpath) is resolved internally to
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283 | the server without any HTTP redirection. The CGI specifications do not
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284 | allow relative URLs in either case.
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285 |
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286 | Use of CGI.pm is strongly recommended. This example shows redirection
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287 | with a complete URL. This redirection is handled by the web browser.
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288 |
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289 | use CGI qw/:standard/;
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290 |
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291 | my $url = 'http://www.cpan.org/';
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292 | print redirect($url);
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293 |
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294 |
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295 | This example shows a redirection with an absolute URLpath. This
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296 | redirection is handled by the local web server.
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297 |
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298 | my $url = '/CPAN/index.html';
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299 | print redirect($url);
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300 |
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301 |
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302 | But if coded directly, it could be as follows (the final "\n" is
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303 | shown separately, for clarity), using either a complete URL or
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304 | an absolute URLpath.
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305 |
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306 | print "Location: $url\n"; # CGI response header
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307 | print "\n"; # end of headers
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308 |
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309 |
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310 | =head2 How do I put a password on my web pages?
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311 |
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312 | To enable authentication for your web server, you need to configure
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313 | your web server. The configuration is different for different sorts
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314 | of web servers---apache does it differently from iPlanet which does
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315 | it differently from IIS. Check your web server documentation for
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316 | the details for your particular server.
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317 |
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318 | =head2 How do I edit my .htpasswd and .htgroup files with Perl?
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319 |
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320 | The HTTPD::UserAdmin and HTTPD::GroupAdmin modules provide a
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321 | consistent OO interface to these files, regardless of how they're
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322 | stored. Databases may be text, dbm, Berkeley DB or any database with
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323 | a DBI compatible driver. HTTPD::UserAdmin supports files used by the
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324 | "Basic" and "Digest" authentication schemes. Here's an example:
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325 |
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326 | use HTTPD::UserAdmin ();
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327 | HTTPD::UserAdmin
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328 | ->new(DB => "/foo/.htpasswd")
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329 | ->add($username => $password);
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330 |
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331 | =head2 How do I make sure users can't enter values into a form that cause my CGI script to do bad things?
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332 |
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333 | See the security references listed in the CGI Meta FAQ
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334 |
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335 | http://www.perl.org/CGI_MetaFAQ.html
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336 |
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337 | =head2 How do I parse a mail header?
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338 |
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339 | For a quick-and-dirty solution, try this solution derived
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340 | from L<perlfunc/split>:
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341 |
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342 | $/ = '';
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343 | $header = <MSG>;
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344 | $header =~ s/\n\s+/ /g; # merge continuation lines
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345 | %head = ( UNIX_FROM_LINE, split /^([-\w]+):\s*/m, $header );
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346 |
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347 | That solution doesn't do well if, for example, you're trying to
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348 | maintain all the Received lines. A more complete approach is to use
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349 | the Mail::Header module from CPAN (part of the MailTools package).
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350 |
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351 | =head2 How do I decode a CGI form?
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352 |
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353 | (contributed by brian d foy)
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354 |
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355 | Use the CGI.pm module that comes with Perl. It's quick,
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356 | it's easy, and it actually does quite a bit of work to
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357 | ensure things happen correctly. It handles GET, POST, and
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358 | HEAD requests, multipart forms, multivalued fields, query
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359 | string and message body combinations, and many other things
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360 | you probably don't want to think about.
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361 |
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362 | It doesn't get much easier: the CGI module automatically
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363 | parses the input and makes each value available through the
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364 | C<param()> function.
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365 |
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366 | use CGI qw(:standard);
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367 |
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368 | my $total = param( 'price' ) + param( 'shipping' );
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369 |
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370 | my @items = param( 'item' ); # multiple values, same field name
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371 |
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372 | If you want an object-oriented approach, CGI.pm can do that too.
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373 |
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374 | use CGI;
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375 |
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376 | my $cgi = CGI->new();
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377 |
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378 | my $total = $cgi->param( 'price' ) + $cgi->param( 'shipping' );
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379 |
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380 | my @items = $cgi->param( 'item' );
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381 |
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382 | You might also try CGI::Minimal which is a lightweight version
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383 | of the same thing. Other CGI::* modules on CPAN might work better
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384 | for you, too.
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385 |
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386 | Many people try to write their own decoder (or copy one from
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387 | another program) and then run into one of the many "gotchas"
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388 | of the task. It's much easier and less hassle to use CGI.pm.
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389 |
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390 | =head2 How do I check a valid mail address?
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391 |
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392 | You can't, at least, not in real time. Bummer, eh?
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393 |
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394 | Without sending mail to the address and seeing whether there's a human
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395 | on the other end to answer you, you cannot determine whether a mail
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396 | address is valid. Even if you apply the mail header standard, you
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397 | can have problems, because there are deliverable addresses that aren't
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398 | RFC-822 (the mail header standard) compliant, and addresses that aren't
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399 | deliverable which are compliant.
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400 |
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401 | You can use the Email::Valid or RFC::RFC822::Address which check
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402 | the format of the address, although they cannot actually tell you
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403 | if it is a deliverable address (i.e. that mail to the address
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404 | will not bounce). Modules like Mail::CheckUser and Mail::EXPN
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405 | try to interact with the domain name system or particular
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406 | mail servers to learn even more, but their methods do not
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407 | work everywhere---especially for security conscious administrators.
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408 |
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409 | Many are tempted to try to eliminate many frequently-invalid
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410 | mail addresses with a simple regex, such as
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411 | C</^[\w.-]+\@(?:[\w-]+\.)+\w+$/>. It's a very bad idea. However,
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412 | this also throws out many valid ones, and says nothing about
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413 | potential deliverability, so it is not suggested. Instead, see
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414 | http://www.cpan.org/authors/Tom_Christiansen/scripts/ckaddr.gz ,
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415 | which actually checks against the full RFC spec (except for nested
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416 | comments), looks for addresses you may not wish to accept mail to
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417 | (say, Bill Clinton or your postmaster), and then makes sure that the
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418 | hostname given can be looked up in the DNS MX records. It's not fast,
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419 | but it works for what it tries to do.
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420 |
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421 | Our best advice for verifying a person's mail address is to have them
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422 | enter their address twice, just as you normally do to change a password.
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423 | This usually weeds out typos. If both versions match, send
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424 | mail to that address with a personal message that looks somewhat like:
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425 |
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426 | Dear [email protected],
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427 |
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428 | Please confirm the mail address you gave us Wed May 6 09:38:41
|
---|
429 | MDT 1998 by replying to this message. Include the string
|
---|
430 | "Rumpelstiltskin" in that reply, but spelled in reverse; that is,
|
---|
431 | start with "Nik...". Once this is done, your confirmed address will
|
---|
432 | be entered into our records.
|
---|
433 |
|
---|
434 | If you get the message back and they've followed your directions,
|
---|
435 | you can be reasonably assured that it's real.
|
---|
436 |
|
---|
437 | A related strategy that's less open to forgery is to give them a PIN
|
---|
438 | (personal ID number). Record the address and PIN (best that it be a
|
---|
439 | random one) for later processing. In the mail you send, ask them to
|
---|
440 | include the PIN in their reply. But if it bounces, or the message is
|
---|
441 | included via a "vacation" script, it'll be there anyway. So it's
|
---|
442 | best to ask them to mail back a slight alteration of the PIN, such as
|
---|
443 | with the characters reversed, one added or subtracted to each digit, etc.
|
---|
444 |
|
---|
445 | =head2 How do I decode a MIME/BASE64 string?
|
---|
446 |
|
---|
447 | The MIME-Base64 package (available from CPAN) handles this as well as
|
---|
448 | the MIME/QP encoding. Decoding BASE64 becomes as simple as:
|
---|
449 |
|
---|
450 | use MIME::Base64;
|
---|
451 | $decoded = decode_base64($encoded);
|
---|
452 |
|
---|
453 | The MIME-Tools package (available from CPAN) supports extraction with
|
---|
454 | decoding of BASE64 encoded attachments and content directly from email
|
---|
455 | messages.
|
---|
456 |
|
---|
457 | If the string to decode is short (less than 84 bytes long)
|
---|
458 | a more direct approach is to use the unpack() function's "u"
|
---|
459 | format after minor transliterations:
|
---|
460 |
|
---|
461 | tr#A-Za-z0-9+/##cd; # remove non-base64 chars
|
---|
462 | tr#A-Za-z0-9+/# -_#; # convert to uuencoded format
|
---|
463 | $len = pack("c", 32 + 0.75*length); # compute length byte
|
---|
464 | print unpack("u", $len . $_); # uudecode and print
|
---|
465 |
|
---|
466 | =head2 How do I return the user's mail address?
|
---|
467 |
|
---|
468 | On systems that support getpwuid, the $< variable, and the
|
---|
469 | Sys::Hostname module (which is part of the standard perl distribution),
|
---|
470 | you can probably try using something like this:
|
---|
471 |
|
---|
472 | use Sys::Hostname;
|
---|
473 | $address = sprintf('%s@%s', scalar getpwuid($<), hostname);
|
---|
474 |
|
---|
475 | Company policies on mail address can mean that this generates addresses
|
---|
476 | that the company's mail system will not accept, so you should ask for
|
---|
477 | users' mail addresses when this matters. Furthermore, not all systems
|
---|
478 | on which Perl runs are so forthcoming with this information as is Unix.
|
---|
479 |
|
---|
480 | The Mail::Util module from CPAN (part of the MailTools package) provides a
|
---|
481 | mailaddress() function that tries to guess the mail address of the user.
|
---|
482 | It makes a more intelligent guess than the code above, using information
|
---|
483 | given when the module was installed, but it could still be incorrect.
|
---|
484 | Again, the best way is often just to ask the user.
|
---|
485 |
|
---|
486 | =head2 How do I send mail?
|
---|
487 |
|
---|
488 | Use the C<sendmail> program directly:
|
---|
489 |
|
---|
490 | open(SENDMAIL, "|/usr/lib/sendmail -oi -t -odq")
|
---|
491 | or die "Can't fork for sendmail: $!\n";
|
---|
492 | print SENDMAIL <<"EOF";
|
---|
493 | From: User Originating Mail <me\@host>
|
---|
494 | To: Final Destination <you\@otherhost>
|
---|
495 | Subject: A relevant subject line
|
---|
496 |
|
---|
497 | Body of the message goes here after the blank line
|
---|
498 | in as many lines as you like.
|
---|
499 | EOF
|
---|
500 | close(SENDMAIL) or warn "sendmail didn't close nicely";
|
---|
501 |
|
---|
502 | The B<-oi> option prevents sendmail from interpreting a line consisting
|
---|
503 | of a single dot as "end of message". The B<-t> option says to use the
|
---|
504 | headers to decide who to send the message to, and B<-odq> says to put
|
---|
505 | the message into the queue. This last option means your message won't
|
---|
506 | be immediately delivered, so leave it out if you want immediate
|
---|
507 | delivery.
|
---|
508 |
|
---|
509 | Alternate, less convenient approaches include calling mail (sometimes
|
---|
510 | called mailx) directly or simply opening up port 25 have having an
|
---|
511 | intimate conversation between just you and the remote SMTP daemon,
|
---|
512 | probably sendmail.
|
---|
513 |
|
---|
514 | Or you might be able use the CPAN module Mail::Mailer:
|
---|
515 |
|
---|
516 | use Mail::Mailer;
|
---|
517 |
|
---|
518 | $mailer = Mail::Mailer->new();
|
---|
519 | $mailer->open({ From => $from_address,
|
---|
520 | To => $to_address,
|
---|
521 | Subject => $subject,
|
---|
522 | })
|
---|
523 | or die "Can't open: $!\n";
|
---|
524 | print $mailer $body;
|
---|
525 | $mailer->close();
|
---|
526 |
|
---|
527 | The Mail::Internet module uses Net::SMTP which is less Unix-centric than
|
---|
528 | Mail::Mailer, but less reliable. Avoid raw SMTP commands. There
|
---|
529 | are many reasons to use a mail transport agent like sendmail. These
|
---|
530 | include queuing, MX records, and security.
|
---|
531 |
|
---|
532 | =head2 How do I use MIME to make an attachment to a mail message?
|
---|
533 |
|
---|
534 | This answer is extracted directly from the MIME::Lite documentation.
|
---|
535 | Create a multipart message (i.e., one with attachments).
|
---|
536 |
|
---|
537 | use MIME::Lite;
|
---|
538 |
|
---|
539 | ### Create a new multipart message:
|
---|
540 | $msg = MIME::Lite->new(
|
---|
541 | From =>'[email protected]',
|
---|
542 | To =>'[email protected]',
|
---|
543 | Cc =>'[email protected], [email protected]',
|
---|
544 | Subject =>'A message with 2 parts...',
|
---|
545 | Type =>'multipart/mixed'
|
---|
546 | );
|
---|
547 |
|
---|
548 | ### Add parts (each "attach" has same arguments as "new"):
|
---|
549 | $msg->attach(Type =>'TEXT',
|
---|
550 | Data =>"Here's the GIF file you wanted"
|
---|
551 | );
|
---|
552 | $msg->attach(Type =>'image/gif',
|
---|
553 | Path =>'aaa000123.gif',
|
---|
554 | Filename =>'logo.gif'
|
---|
555 | );
|
---|
556 |
|
---|
557 | $text = $msg->as_string;
|
---|
558 |
|
---|
559 | MIME::Lite also includes a method for sending these things.
|
---|
560 |
|
---|
561 | $msg->send;
|
---|
562 |
|
---|
563 | This defaults to using L<sendmail> but can be customized to use
|
---|
564 | SMTP via L<Net::SMTP>.
|
---|
565 |
|
---|
566 | =head2 How do I read mail?
|
---|
567 |
|
---|
568 | While you could use the Mail::Folder module from CPAN (part of the
|
---|
569 | MailFolder package) or the Mail::Internet module from CPAN (part
|
---|
570 | of the MailTools package), often a module is overkill. Here's a
|
---|
571 | mail sorter.
|
---|
572 |
|
---|
573 | #!/usr/bin/perl
|
---|
574 |
|
---|
575 | my(@msgs, @sub);
|
---|
576 | my $msgno = -1;
|
---|
577 | $/ = ''; # paragraph reads
|
---|
578 | while (<>) {
|
---|
579 | if (/^From /m) {
|
---|
580 | /^Subject:\s*(?:Re:\s*)*(.*)/mi;
|
---|
581 | $sub[++$msgno] = lc($1) || '';
|
---|
582 | }
|
---|
583 | $msgs[$msgno] .= $_;
|
---|
584 | }
|
---|
585 | for my $i (sort { $sub[$a] cmp $sub[$b] || $a <=> $b } (0 .. $#msgs)) {
|
---|
586 | print $msgs[$i];
|
---|
587 | }
|
---|
588 |
|
---|
589 | Or more succinctly,
|
---|
590 |
|
---|
591 | #!/usr/bin/perl -n00
|
---|
592 | # bysub2 - awkish sort-by-subject
|
---|
593 | BEGIN { $msgno = -1 }
|
---|
594 | $sub[++$msgno] = (/^Subject:\s*(?:Re:\s*)*(.*)/mi)[0] if /^From/m;
|
---|
595 | $msg[$msgno] .= $_;
|
---|
596 | END { print @msg[ sort { $sub[$a] cmp $sub[$b] || $a <=> $b } (0 .. $#msg) ] }
|
---|
597 |
|
---|
598 | =head2 How do I find out my hostname, domainname, or IP address?
|
---|
599 | X<hostname, domainname, IP address, host, domain, hostfqdn, inet_ntoa,
|
---|
600 | gethostbyname, Socket, Net::Domain, Sys::Hostname>
|
---|
601 |
|
---|
602 | (contributed by brian d foy)
|
---|
603 |
|
---|
604 | The Net::Domain module, which is part of the standard distribution starting
|
---|
605 | in perl5.7.3, can get you the fully qualified domain name (FQDN), the host
|
---|
606 | name, or the domain name.
|
---|
607 |
|
---|
608 | use Net::Domain qw(hostname hostfqdn hostdomain);
|
---|
609 |
|
---|
610 | my $host = hostfqdn();
|
---|
611 |
|
---|
612 | The C<Sys::Hostname> module, included in the standard distribution since
|
---|
613 | perl5.6, can also get the hostname.
|
---|
614 |
|
---|
615 | use Sys::Hostname;
|
---|
616 |
|
---|
617 | $host = hostname();
|
---|
618 |
|
---|
619 | To get the IP address, you can use the C<gethostbyname> built-in function
|
---|
620 | to turn the name into a number. To turn that number into the dotted octet
|
---|
621 | form (a.b.c.d) that most people expect, use the C<inet_ntoa> function
|
---|
622 | from the <Socket> module, which also comes with perl.
|
---|
623 |
|
---|
624 | use Socket;
|
---|
625 |
|
---|
626 | my $address = inet_ntoa(
|
---|
627 | scalar gethostbyname( $host || 'localhost' )
|
---|
628 | );
|
---|
629 |
|
---|
630 | =head2 How do I fetch a news article or the active newsgroups?
|
---|
631 |
|
---|
632 | Use the Net::NNTP or News::NNTPClient modules, both available from CPAN.
|
---|
633 | This can make tasks like fetching the newsgroup list as simple as
|
---|
634 |
|
---|
635 | perl -MNews::NNTPClient
|
---|
636 | -e 'print News::NNTPClient->new->list("newsgroups")'
|
---|
637 |
|
---|
638 | =head2 How do I fetch/put an FTP file?
|
---|
639 |
|
---|
640 | LWP::Simple (available from CPAN) can fetch but not put. Net::FTP (also
|
---|
641 | available from CPAN) is more complex but can put as well as fetch.
|
---|
642 |
|
---|
643 | =head2 How can I do RPC in Perl?
|
---|
644 |
|
---|
645 | (Contributed by brian d foy)
|
---|
646 |
|
---|
647 | Use one of the RPC modules you can find on CPAN (
|
---|
648 | http://search.cpan.org/search?query=RPC&mode=all ).
|
---|
649 |
|
---|
650 | =head1 AUTHOR AND COPYRIGHT
|
---|
651 |
|
---|
652 | Copyright (c) 1997-2006 Tom Christiansen, Nathan Torkington, and
|
---|
653 | other authors as noted. All rights reserved.
|
---|
654 |
|
---|
655 | This documentation is free; you can redistribute it and/or modify it
|
---|
656 | under the same terms as Perl itself.
|
---|
657 |
|
---|
658 | Irrespective of its distribution, all code examples in this file
|
---|
659 | are hereby placed into the public domain. You are permitted and
|
---|
660 | encouraged to use this code in your own programs for fun
|
---|
661 | or for profit as you see fit. A simple comment in the code giving
|
---|
662 | credit would be courteous but is not required.
|
---|