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Index: U

• unbuffering output stream: Unbuffer Output Stream
• undef vs. (): undef Versus ( )
• underscores (_)
• • filenames, replacing characters with: File Uploads with CGI.pm
  • nonalphanumeric parameter name characters, replacing with: Exporting Parameters to a Namespace
  • use in Perl: Coding Guidelines
• Unicode-compliant data transport, XML: An Introduction to XML
• unique identifiers
• • generating for sessions: Hidden Fields
  • in hidden field: Hidden Fields
  • inserting into HTML documents, module for: Query Strings and Extra Path Information
  • mod_unique_id module, building with: Query Strings and Extra Path Information
  • passing with HTTP requests: Maintaining State
• Unisys patent on LZW compression algorithm: The LZW patent
• Unix operating system
• • binmode function, not supporting: binmode
  • ColdFusion language, versions for: Alternatives to CGI
  • commands to locate perl: The Pound-Bang
  • executable files, commands for: Invoking CGI Scripts
  • executables, differentiating in filesystem: Invoking CGI Scripts
  • file permissions: Write Permissions
  • forward slashes (/) separating directories: Search Application
  • Perl
  • • linefeed and carriage return, representing on: Outputting documents
    • speediness on: Why Perl?
  • sendmail on: sendmail
  • uptime command: Using GD
  • variables (see environment variables)
• unsolicited bulk email (see spam)
• untainting data: How Taintedness Is Removed
• • fgrep command search: Searching One by One
• untying hash tables from database files: DB_File
• update query screen: Address tutorial CGI script
• updating databases: Updating Data
• updating HTML documents with links: Specifying an alternative target
• upload method (CGI.pm): File Uploads with CGI.pm
• UPLOAD_DIR: File Uploads with CGI.pm
• uploading files
• • handling with CGI.pm: File Uploads with CGI.pm
• uppercase, use in request methods: The Request Line
• uptime Unix system command: Using GD
• • Using GD
• URI module: IO::Socket
• URIs (Uniform Resource Identifiers): URLs
• URI::URL module: URL Encoding
• url method (CGI.pm): url
• url_escape and url_unescape functions: URL Encoding
• URLs (Uniform Resource Locators): History
• • URLs
  • absolute and relative: Absolute and Relative URLs
  • base for relative URLs in HTML documents: Content-Base
  • tutorialmarklets, JavaScript: Bookmarklets
  • breaking into components with URI module: IO::Socket
  • CGI scripts: Invoking CGI Scripts
  • • calling from, self_url method and: self_url
    • pointing to with tag: start_html
    • specifying for receiving HTTP requests: The <FORM> Tag
  • components of: Elements of a URL
  • • fragment identifiers: Elements of a URL
    • hosts: Elements of a URL
    • path information: Elements of a URL
    • port numbers: Elements of a URL
    • scheme (protocol): Elements of a URL
  • to embpcgi.pl script: embpcgi.pl
  • encoded characters: Decoding Form Input
  • encoding characters in: URL Encoding
  • • URI::URL module: URL Encoding
  • forwarding users to with Location header: Forwarding to another URL
  • getting data from with LWP module: CGI Gateway to XML Middleware
  • image displayed for image button, specifying: Image buttons
  • invalid, 404 status code responses and: Specifying status codes
  • IP addresses, problems with using in: Elements of a URL
  • last page visited by user (Referer field): Referer
  • manually constructed, passing parameters without equal (=) sign: Decoding Form Input
  • parameters, visibility in GET requests: Trusting the Browser
  • paths: Search Application
  • • extra information, maintaining state with: Query Strings and Extra Path Information
    • mapping to CGI script directory on disk: Configuring by directory
    • passing unique identifiers as extra information: Maintaining State
  • query strings in: Elements of a URL
  • • Sending Data to the Server
    • Decoding Form Input
    • POST and the query string
  • redirection with redirect method: Redirection
  • related to current, looking up with Netscape browser: Writing an XML Parser
  • relative, advantages of: Use Relative URLs
  • of requested resources, changed: Specifying status codes
  • • Specifying status codes
  • specifying for tag: start_html
  • text, encoding: Sending Data to the Server
  • unique identifier embedded in: Query Strings and Extra Path Information
  • #USERID# as identifier for documents: Query Strings and Extra Path Information
• URNs (Uniform Resource Names): URLs
• use statement: Connecting to DBI
• use strict command: Sample CGI
• use vars statement: Address tutorial CGI script
• user agent, creating with LWP: LWP
• User-Agent field: User-Agent
• user file, user names and encrypted passwords in: Authorization
• user registration form (example): Validation example
• user session: Maintaining State
• usernames: WWW-Authenticate
• users
• • authentication and identification (script): User Authentication and Identification
  • email permissions, security risks of: False Identities
  • error information, limiting view of: CGI::Carp
  • input
  • • tainted data, checking for: How Taint Works
  • input from
  • • handling securely: Handling User Input
    • untainting: How Taintedness Is Removed
  • tracking: Maintaining State
  • web servers running as: Command-Line Options

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