doc/tutorial.html

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   5 >Libpwmd Tutorial</TITLE
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   9 ><BODY
  10 CLASS="ARTICLE"
  11 ><DIV
  12 CLASS="ARTICLE"
  13 ><DIV
  14 CLASS="TITLEPAGE"
  15 ><H1
  16 CLASS="TITLE"
  17 ><A
  18 NAME="AEN2"
  19 >Libpwmd Tutorial</A
  20 ></H1
  21 ><H3
  22 CLASS="AUTHOR"
  23 ><A
  24 NAME="AEN5"
  25 ></A
  26 ></H3
  27 ><HR></DIV
  28 ><DIV
  29 CLASS="SECT1"
  30 ><H2
  31 CLASS="SECT1"
  32 ><A
  33 NAME="AEN9"
  34 >Introduction</A
  35 ></H2
  36 ><P
  37 >This is a tutorial showing the basic usage of libpwmd<A
  38 NAME="AEN12"
  39 HREF="#FTN.AEN12"
  40 ><SPAN
  41 CLASS="footnote"
  42 >[2]</SPAN
  43 ></A
  44 >. Libpwmd<SPAN
  45 CLASS="emphasis"
  46 ><I
  47 CLASS="EMPHASIS"
  48 > </I
  49 ></SPAN
  50 >is a library making it easy to access pwmd<A
  51 NAME="AEN15"
  52 HREF="#FTN.AEN15"
  53 ><SPAN
  54 CLASS="footnote"
  55 >[3]</SPAN
  56 ></A
  57 > or <SPAN
  58 CLASS="emphasis"
  59 ><I
  60 CLASS="EMPHASIS"
  61 >Password Manager Daemon</I
  62 ></SPAN
  63 >.</P
  64 ></DIV
  65 ><DIV
  66 CLASS="SECT1"
  67 ><HR><H2
  68 CLASS="SECT1"
  69 ><A
  70 NAME="AEN18"
  71 >What is PWMD?</A
  72 ></H2
  73 ><P
  74 ><SPAN
  75 CLASS="emphasis"
  76 ><I
  77 CLASS="EMPHASIS"
  78 >Password Manager Daemon</I
  79 ></SPAN
  80 > is a universal data server. It began as a way to keep track of my passwords for accounts like email and websites but can be used to store anything you want.</P
  81 ><P
  82 >There are other password management tools but pwmd has a couple of distinguishing features:</P
  83 ><P
  84 ></P
  85 ><UL
  86 ><LI
  87 ><P
  88 >It does not depend on a desktop environment but has the ability for applications to connect to it like a desktop solution provides.</P
  89 ></LI
  90 ><LI
  91 ><P
  92 >Some portion of a stored data can be shared with another portion in the same data file. This feature behaves a lot like a symbolic link on a file system, XML entities, or HTML targets if you're familiar with those, but implemented in a different way.</P
  93 ></LI
  94 ></UL
  95 ></DIV
  96 ><DIV
  97 CLASS="SECT1"
  98 ><HR><H2
  99 CLASS="SECT1"
 100 ><A
 101 NAME="AEN28"
 102 >Element paths</A
 103 ></H2
 104 ><P
 105 >The document is saved as an XML file and is manipulated by commands sent from a client. Commands that access data take what is called an <SPAN
 106 CLASS="emphasis"
 107 ><I
 108 CLASS="EMPHASIS"
 109 >element path</I
 110 ></SPAN
 111 > as an argument. An element path is a character string containing XML element names representing branches of an element tree. The branches are separated with a TAB (ASCII 0x09) character. Why a TAB? So other characters can be used in the element name. If for example a '/' were used as the separator, then a URL (i.e., http://sf.net/) could not be used as an element name.</P
 112 ><P
 113 >For the rest of this tutorial, when you see &lt;TAB&gt;, replace it with a real TAB character. For example, the element path "a&lt;TAB&gt;child&lt;TAB&gt;last" has the following element tree:</P
 114 ><TABLE
 115 BORDER="0"
 116 BGCOLOR="#E0E0E0"
 117 WIDTH="100%"
 118 ><TR
 119 ><TD
 120 ><PRE
 121 CLASS="SCREEN"
 122 >&#60;a&#62;
 123     &#60;child&#62;
 124         &#60;last&#62;
 125 Content or XML CDATA of the "last" element.
 126         &#60;/last&#62;
 127     &#60;/child&#62;
 128 &#60;/a&#62;</PRE
 129 ></TD
 130 ></TR
 131 ></TABLE
 132 ><P
 133 >I should say that the XML structure that pwmd uses is a little more complicated. It really looks like the following internally, but we will use the above format in this tutorial for simplicity:</P
 134 ><TABLE
 135 BORDER="0"
 136 BGCOLOR="#E0E0E0"
 137 WIDTH="100%"
 138 ><TR
 139 ><TD
 140 ><PRE
 141 CLASS="SCREEN"
 142 >&#60;element _name="a"&#62;
 143     &#60;element _name="child"&#62;
 144         &#60;element _name="last"&#62;Content or CDATA of the "last" element.
 145         &#60;/element&#62;
 146     &#60;/element&#62;
 147 &#60;/element&#62;</PRE
 148 ></TD
 149 ></TR
 150 ></TABLE
 151 ><P
 152 >Every element created has an element named <SPAN
 153 CLASS="emphasis"
 154 ><I
 155 CLASS="EMPHASIS"
 156 >element</I
 157 ></SPAN
 158 > with an attribute <SPAN
 159 CLASS="emphasis"
 160 ><I
 161 CLASS="EMPHASIS"
 162 >_name</I
 163 ></SPAN
 164 > associated with it. The value of the <SPAN
 165 CLASS="emphasis"
 166 ><I
 167 CLASS="EMPHASIS"
 168 >_name</I
 169 ></SPAN
 170 > attribute is what an element in an element path refers to. It is done this way so that a wider range of characters can be used in an element name while maintaining valid XML. In fact, the only restriction of an element name is that it not contain whitespace characters and not begin with an exclamation point (ASCII 0x21 or !). See <SPAN
 171 CLASS="emphasis"
 172 ><I
 173 CLASS="EMPHASIS"
 174 ><A
 175 HREF="#SEC.LINKING-ELEMENTS-1"
 176 >the Section called <I
 177 >Linking elements</I
 178 ></A
 179 > </I
 180 ></SPAN
 181 >for an exception.</P
 182 ><P
 183 >There is one other difference from your normal XML document in that only the first match of an element is considered for the current element tree depth. When an element of the current depth of an element tree is found, the next element in the element path is searched for beginning at the child node of the found element. From the example above:</P
 184 ><TABLE
 185 BORDER="0"
 186 BGCOLOR="#E0E0E0"
 187 WIDTH="100%"
 188 ><TR
 189 ><TD
 190 ><PRE
 191 CLASS="SCREEN"
 192 >&#60;a&#62;
 193     &#60;child&#62;
 194         &#60;last&#62;Content or XML CDATA of the "last" element.
 195         &#60;/last&#62;
 196     &#60;/child&#62;
 197     &#60;child&#62;This element will never be reached.
 198     &#60;/child&#62;
 199 &#60;/a&#62;</PRE
 200 ></TD
 201 ></TR
 202 ></TABLE
 203 ><P
 204 >The second "child" element is never reached, although an element of a different name may be accessed.</P
 205 ></DIV
 206 ><DIV
 207 CLASS="SECT1"
 208 ><HR><H2
 209 CLASS="SECT1"
 210 ><A
 211 NAME="AEN45"
 212 >Clients</A
 213 ></H2
 214 ><P
 215 >You will need a client to send commands to the pwmd server. If you are making your own application or need a simple client to connect to the server then <SPAN
 216 CLASS="emphasis"
 217 ><I
 218 CLASS="EMPHASIS"
 219 >libpwmd</I
 220 ></SPAN
 221 > may be used. It has few dependencies and - as mentioned - includes a client named <SPAN
 222 CLASS="emphasis"
 223 ><I
 224 CLASS="EMPHASIS"
 225 >pwmc</I
 226 ></SPAN
 227 >. The rest of this tutorial will use pwmc. It is command-line based and there are not any fancy graphics, but it is good for understanding how commands are processed.</P
 228 ><P
 229 >If you want a more user friendly client that looks like a file manager and has a point and click interface, try pwmdEdit<A
 230 NAME="AEN51"
 231 HREF="#FTN.AEN51"
 232 ><SPAN
 233 CLASS="footnote"
 234 >[4]</SPAN
 235 ></A
 236 > which uses the Qt4 toolkit.</P
 237 ></DIV
 238 ><DIV
 239 CLASS="SECT1"
 240 ><HR><H2
 241 CLASS="SECT1"
 242 ><A
 243 NAME="AEN53"
 244 >Connecting</A
 245 ></H2
 246 ><P
 247 >We are using the <SPAN
 248 CLASS="emphasis"
 249 ><I
 250 CLASS="EMPHASIS"
 251 >pwmc</I
 252 ></SPAN
 253 > client included in libpwmd. pwmc has two modes that commands are read from: interactive and stdin. The interactive mode uses the readline library and has command history while reading from standard input (stdin) makes shell scripting and automation easy. For the examples, we will be connecting to the default local unix domain socket that pwmd waits for connections on. Remote connections are possible over an SSH channel but that is not covered here. Read the pwmc(1) manual page for how to do that.</P
 254 ><P
 255 >The example filename we will use is "datafile". It is initially a non-existent file but it will be created once we have saved to it. Now let us connect to the server in interactive mode and open the data file:</P
 256 ><TABLE
 257 BORDER="0"
 258 BGCOLOR="#E0E0E0"
 259 WIDTH="100%"
 260 ><TR
 261 ><TD
 262 ><PRE
 263 CLASS="SCREEN"
 264 >$ pwmc --interactive datafile
 265 Connected.
 266 pwm&#62;</PRE
 267 ></TD
 268 ></TR
 269 ></TABLE
 270 ><P
 271 >The "pwm&gt;" prompt is a readline prompt that has command history and can do filename completion. It also is annoying because, as mentioned, elements in element paths are TAB delimited, but command completion in readline uses the TAB character, too. To insert a real TAB character in interactive mode rather than do readline completion, you will need to first press CTRL-V and then press TAB.</P
 272 ></DIV
 273 ><DIV
 274 CLASS="SECT1"
 275 ><HR><H2
 276 CLASS="SECT1"
 277 ><A
 278 NAME="AEN60"
 279 >Commands</A
 280 ></H2
 281 ><P
 282 >To store some data in an element path, you will need to know what element path to create. It is up to you how you want your data organized. If for example you will be storing account information it may be a good idea to categorize what the account is for: email, instant messaging, blogging, etc.</P
 283 ><P
 284 >In the following example we will setup mail server element paths which can be used for other applications requiring a mail server configuration. First, lets create the hostname element path:</P
 285 ><TABLE
 286 BORDER="0"
 287 BGCOLOR="#E0E0E0"
 288 WIDTH="100%"
 289 ><TR
 290 ><TD
 291 ><PRE
 292 CLASS="SCREEN"
 293 >pwm&#62; STORE</PRE
 294 ></TD
 295 ></TR
 296 ></TABLE
 297 ><P
 298 >The STORE command is a pwmd protocol command. This command and some other commands use what is called a <SPAN
 299 CLASS="emphasis"
 300 ><I
 301 CLASS="EMPHASIS"
 302 >server inquire</I
 303 ></SPAN
 304 > to retrieve data from the client, while other commands may retrieve required data only from the command arguments. The server inquire will wait for the client to finish sending its data before completing the command. When responding to a server inquire in pwmc, pwmc will show a message telling you that it is waiting for data to be sent. Enter the element path and its content, then press &lt;CTRL-D&gt; twice to finish sending the data and let pwmd complete the command:</P
 305 ><TABLE
 306 BORDER="0"
 307 BGCOLOR="#E0E0E0"
 308 WIDTH="100%"
 309 ><TR
 310 ><TD
 311 ><PRE
 312 CLASS="SCREEN"
 313 >pwm&#62; STORE
 314 email&#60;TAB&#62;isp&#60;TAB&#62;IMAP&#60;TAB&#62;hostname&#60;TAB&#62;imap.server.com&#60;CTRL-D&#62;&#60;CTRL-D&#62;</PRE
 315 ></TD
 316 ></TR
 317 ></TABLE
 318 ><P
 319 >Remember that you should replace &lt;TAB&gt; in the examples with a real TAB character. I should mention that when sending data via a server inquire there is no need to press CTRL-V to insert the TAB character. That is only needed from the readline command prompt and when not doing a server inquire.</P
 320 ><P
 321 >After pressing the first CTRL-D, the line that was entered is sent to pwmd and the inquire continues. To terminate the inquire and finish sending data for the command, press CTRL-D a second time.</P
 322 ><P
 323 >If you were to have pressed RETURN before any CTRL-D then the inquired line would have been sent in full including a newline character. Since in this example a newline character in a hostname is not a valid hostname, this is not what we want.</P
 324 ><P
 325 >We have just created an element path whose XML structure looks like the following:</P
 326 ><TABLE
 327 BORDER="0"
 328 BGCOLOR="#E0E0E0"
 329 WIDTH="100%"
 330 ><TR
 331 ><TD
 332 ><PRE
 333 CLASS="SCREEN"
 334 >&#60;email&#62;
 335     &#60;isp&#62;
 336         &#60;IMAP&#62;
 337             &#60;hostname&#62;imap.server.com&#60;/hostname&#62;
 338         &#60;/IMAP&#62;
 339     &#60;/isp&#62;
 340 &#60;/email&#62;</PRE
 341 ></TD
 342 ></TR
 343 ></TABLE
 344 ><P
 345 >When an application needs to retrieve the content for the element path we have just created, it will send the GET command (libpwmd does this part) to the pwmd server. You can retrieve the content of an element path by using the GET command in pwmc, too:</P
 346 ><TABLE
 347 BORDER="0"
 348 BGCOLOR="#E0E0E0"
 349 WIDTH="100%"
 350 ><TR
 351 ><TD
 352 ><PRE
 353 CLASS="SCREEN"
 354 >pwm&#62; GET email&#60;TAB&#62;isp&#60;TAB&#62;IMAP&#60;TAB&#62;hostname
 355 XFER 0 15
 356 XFER 15 15
 357 imap.server.com</PRE
 358 ></TD
 359 ></TR
 360 ></TABLE
 361 ><P
 362 >Remember that in interactive mode and when not doing a server inquire, you will need to press CTRL-V before pressing TAB.</P
 363 ><P
 364 >The XFER lines are status messages. They show the current and total length of the data transfered in bytes. The last line is the value of the element path we just created.</P
 365 ><P
 366 >Let us create the rest of the needed elements:</P
 367 ><TABLE
 368 BORDER="0"
 369 BGCOLOR="#E0E0E0"
 370 WIDTH="100%"
 371 ><TR
 372 ><TD
 373 ><PRE
 374 CLASS="SCREEN"
 375 >pwm&#62; STORE email&#60;TAB&#62;isp&#60;TAB&#62;IMAP&#60;TAB&#62;port&#60;TAB&#62;993&#60;CTRL-D&#62;&#60;CTRL-D&#62;
 376 pwm&#62; STORE
 377 email&#60;TAB&#62;isp&#60;TAB&#62;IMAP&#60;TAB&#62;ssl&#60;TAB&#62;1&#60;CTRL-D&#62;&#60;CTRL-D&#62;
 378 pwm&#62; STORE
 379 email&#60;TAB&#62;isp&#60;TAB&#62;username&#60;TAB&#62;myusername&#60;CTRL-D&#62;&#60;CTRL-D&#62;
 380 pwm&#62; STORE
 381 email&#60;TAB&#62;isp&#60;TAB&#62;password&#60;TAB&#62;mypassword&#60;CTRL-D&#62;&#60;CTRL-D&#62;</PRE
 382 ></TD
 383 ></TR
 384 ></TABLE
 385 ><P
 386 >Now the element structure for the root "email" element looks like this:</P
 387 ><TABLE
 388 BORDER="0"
 389 BGCOLOR="#E0E0E0"
 390 WIDTH="100%"
 391 ><TR
 392 ><TD
 393 ><PRE
 394 CLASS="SCREEN"
 395 >&#60;email&#62;
 396     &#60;isp&#62;
 397         &#60;IMAP&#62;
 398               &#60;hostname&#62;imap.server.com&#60;/hostname&#62;
 399               &#60;port&#62;993&#60;/port&#62;
 400               &#60;ssl&#62;1&#60;/ssl&#62;
 401         &#60;/IMAP&#62;
 402         &#60;username&#62;myusername&#60;/username&#62;
 403         &#60;password&#62;mypassword&#60;/password&#62;
 404     &#60;/isp&#62;
 405 &#60;/email&#62;</PRE
 406 ></TD
 407 ></TR
 408 ></TABLE
 409 ><P
 410 >If you wanted to change your password (after changing it on the mail server, of course) just do as you did when initially creating the password element path. The new content will overwrite the existing content:</P
 411 ><TABLE
 412 BORDER="0"
 413 BGCOLOR="#E0E0E0"
 414 WIDTH="100%"
 415 ><TR
 416 ><TD
 417 ><PRE
 418 CLASS="SCREEN"
 419 >pwm&#62; STORE
 420 email&#60;TAB&#62;isp&#60;TAB&#62;password&#60;TAB&#62;newpassword&#60;CTRL-D&#62;&#60;CTRL-D&#62;</PRE
 421 ></TD
 422 ></TR
 423 ></TABLE
 424 ><P
 425 >An application using libpwmd that needs to know mail server information now has all the information it needs. The only thing left to do now is to save the changes:</P
 426 ><TABLE
 427 BORDER="0"
 428 BGCOLOR="#E0E0E0"
 429 WIDTH="100%"
 430 ><TR
 431 ><TD
 432 ><PRE
 433 CLASS="SCREEN"
 434 >pwm&#62; &#60;CTRL-D&#62;</PRE
 435 ></TD
 436 ></TR
 437 ></TABLE
 438 ><P
 439 >After pressing &lt;CTRL-D&gt; a prompt will be shown asking what to do. Press &ldquo;s&rdquo; to save what we have created.</P
 440 ><P
 441 >Since this is a new file, you will be prompted for a passphrase to use for encryption. Once done, the data file is encrypted and written to disk and the passphrase is cached in pwmd so you do not need to enter it the next time your data file is opened or saved. There are a few pwmd configuration parameters that affect how this operates. See the pwmd documentation for details.</P
 442 ><P
 443 >Various applications using libpwmd may have different element path requirements. Refer to the documentation of each application that supports pwmd for the required elements.</P
 444 ></DIV
 445 ><DIV
 446 CLASS="SECT1"
 447 ><HR><H2
 448 CLASS="SECT1"
 449 ><A
 450 NAME="SEC.LINKING-ELEMENTS-1"
 451 >Linking elements</A
 452 ></H2
 453 ><P
 454 >One distinguishing feature of pwmd is the ability to share data of an element path with another. For example, if your ISP lets you host a blog on their server and you use a blogging client that supports pwmd to edit your posts, you can share authentication information with the email example above when the account details are the same. When element linking is used, this avoids the need to change the content for both the blogging and email password elements.</P
 455 ><P
 456 >This is done by setting a special &ldquo;target&rdquo; attribute for an element. It behaves similarly to the HTML &ldquo;target&rdquo; attribute or XML entities or a symbolic link on a filesystem. </P
 457 ><P
 458 >Let's create an example blogging element path:</P
 459 ><TABLE
 460 BORDER="0"
 461 BGCOLOR="#E0E0E0"
 462 WIDTH="100%"
 463 ><TR
 464 ><TD
 465 ><PRE
 466 CLASS="SCREEN"
 467 >pwm&#62; STORE
 468 blog&#60;TAB&#62;isp&#60;TAB&#62;hostname&#60;TAB&#62;blog.myisp.com&#60;CTRL-D&#62;&#60;CTRL-D&#62;
 469
 470 pwm&#62; ATTR SET target blog&#60;TAB&#62;isp&#60;TAB&#62;username email&#60;TAB&#62;isp&#60;TAB&#62;username
 471 pwm&#62; ATTR SET target blog&#60;TAB&#62;isp&#60;TAB&#62;password email&#60;TAB&#62;isp&#60;TAB&#62;password</PRE
 472 ></TD
 473 ></TR
 474 ></TABLE
 475 ><P
 476 >Now each access of the "blog/isp/username" and "blog/isp/password" element paths, which were created if they did not already exist, will point to "email/isp/username" and "email/isp/password" respectively. To get the value or content of an element that contains a "target" attribute without following any &ldquo;target&rdquo; attribute, prefix the element with a '!' when specifying it in an element path. For example:</P
 477 ><TABLE
 478 BORDER="0"
 479 BGCOLOR="#E0E0E0"
 480 WIDTH="100%"
 481 ><TR
 482 ><TD
 483 ><PRE
 484 CLASS="SCREEN"
 485 >pwm&#62; GET blog&#60;TAB&#62;isp&#60;TAB&#62;!password
 486 ERR 536870938: No value</PRE
 487 ></TD
 488 ></TR
 489 ></TABLE
 490 ><P
 491 >An error is returned because we have not assigned a value to the literal element. A literal element is an element that either contains no "target" attribute or ignores it by prefixing the element with the mentioned literal element character '!'. Let us try storing an example password to the literal element to show usage:</P
 492 ><TABLE
 493 BORDER="0"
 494 BGCOLOR="#E0E0E0"
 495 WIDTH="100%"
 496 ><TR
 497 ><TD
 498 ><PRE
 499 CLASS="SCREEN"
 500 >pwmd&#62; STORE
 501 blog&#60;TAB&#62;isp&#60;TAB&#62;!password&#60;TAB&#62;newpassword&#60;CTRL-D&#62;&#60;CTRL-D&#62;</PRE
 502 ></TD
 503 ></TR
 504 ></TABLE
 505 ><P
 506 >Now when we redo the previous GET command:</P
 507 ><TABLE
 508 BORDER="0"
 509 BGCOLOR="#E0E0E0"
 510 WIDTH="100%"
 511 ><TR
 512 ><TD
 513 ><PRE
 514 CLASS="SCREEN"
 515 >pwm&#62; GET blog&#60;TAB&#62;isp&#60;TAB&#62;!password
 516 XFER 0 11
 517 XFER 11 11
 518 newpassword</PRE
 519 ></TD
 520 ></TR
 521 ></TABLE
 522 ><P
 523 >This is the value of the literal password element of the element path. To follow the element path stored in the "target" attribute, omit the '!' in the password element. This will return the &ldquo;email/isp/password&rdquo; element content:</P
 524 ><TABLE
 525 BORDER="0"
 526 BGCOLOR="#E0E0E0"
 527 WIDTH="100%"
 528 ><TR
 529 ><TD
 530 ><PRE
 531 CLASS="SCREEN"
 532 >pwm&#62; GET blog&#60;TAB&#62;isp&#60;TAB&#62;password
 533 XFER 0 10
 534 XFER 10 10
 535 mypassword</PRE
 536 ></TD
 537 ></TR
 538 ></TABLE
 539 ><P
 540 >A "target" attribute may also refer to another element with a "target" attribute. Every "target" attribute will be followed until there are no others to resolve. To get the real element path and resolve all "target" attributes, use the REALPATH command:</P
 541 ><TABLE
 542 BORDER="0"
 543 BGCOLOR="#E0E0E0"
 544 WIDTH="100%"
 545 ><TR
 546 ><TD
 547 ><PRE
 548 CLASS="SCREEN"
 549 >pwm&#62; REALPATH blog&#60;TAB&#62;isp&#60;TAB&#62;password
 550 XFER 0 30
 551 XFER 30 30
 552 !email&#60;TAB&#62;!isp&#60;TAB&#62;!password</PRE
 553 ></TD
 554 ></TR
 555 ></TABLE
 556 ><P
 557 >As you can see each element is prefixed with the literal '!' character meaning that no "target" attribute exists in any element of the resulting element path.</P
 558 ><P
 559 >Using the LIST command is useful to show the element structure of a document. The XFER status messages have been omitted:</P
 560 ><TABLE
 561 BORDER="0"
 562 BGCOLOR="#E0E0E0"
 563 WIDTH="100%"
 564 ><TR
 565 ><TD
 566 ><PRE
 567 CLASS="SCREEN"
 568 >pwm&#62; LIST
 569 !email
 570 !blog
 571 pwm&#62; LIST !email
 572 !email
 573 !email&#60;TAB&#62;!isp
 574 !email&#60;TAB&#62;!isp&#60;TAB&#62;!username
 575 !email&#60;TAB&#62;!isp&#60;TAB&#62;!password
 576 !email&#60;TAB&#62;!isp&#60;TAB&#62;!IMAP&#60;TAB&#62;!hostname
 577 !email&#60;TAB&#62;!isp&#60;TAB&#62;!IMAP&#60;TAB&#62;!port
 578 !email&#60;TAB&#62;!isp&#60;TAB&#62;!IMAP&#60;TAB&#62;!ssl
 579 pwm&#62; LIST !blog
 580 !blog
 581 !blog&#60;TAB&#62;!isp
 582 !blog&#60;TAB&#62;!isp&#60;TAB&#62;!username
 583 !blog&#60;TAB&#62;!isp&#60;TAB&#62;username
 584 !blog&#60;TAB&#62;!isp&#60;TAB&#62;!password
 585 !blog&#60;TAB&#62;!isp&#60;TAB&#62;password</PRE
 586 ></TD
 587 ></TR
 588 ></TABLE
 589 ><P
 590 >Notice that there are two username and password elements in the &ldquo;blog&rdquo; element path: each with and without the literal element character prefix. This shows that both the username and password elements contain a "target" attribute.</P
 591 ><P
 592 >For the final example, we will remove the &ldquo;target&rdquo; attribute of the blogging password element:</P
 593 ><TABLE
 594 BORDER="0"
 595 BGCOLOR="#E0E0E0"
 596 WIDTH="100%"
 597 ><TR
 598 ><TD
 599 ><PRE
 600 CLASS="SCREEN"
 601 >pwm&#62; ATTR DELETE target blog&#60;TAB&#62;isp&#60;TAB&#62;!password</PRE
 602 ></TD
 603 ></TR
 604 ></TABLE
 605 ><P
 606 >If we were to have omitted the '!' from the password element then pwmd would try to remove the "target" attribute from the "email/isp/password" element path. That would return an error because no &ldquo;target&rdquo; attribute had been set for that element.</P
 607 ><P
 608 >Note that the "blog" and "isp" elements have no literal element character prepended to them in the example. It is not needed because they have no &ldquo;target&rdquo; attribute themselves.</P
 609 ><P
 610 >Using &ldquo;target&rdquo; attributes can be confusing. The best way to get the hang of linking elements is to experiment and use the LIST and DUMP commands to show the document structure. Remember to use the literal element prefix '!' when you do not want to follow any "target" attributes.</P
 611 ></DIV
 612 ></DIV
 613 ><H3
 614 CLASS="FOOTNOTES"
 615 >Notes</H3
 616 ><TABLE
 617 BORDER="0"
 618 CLASS="FOOTNOTES"
 619 WIDTH="100%"
 620 ><TR
 621 ><TD
 622 ALIGN="LEFT"
 623 VALIGN="TOP"
 624 WIDTH="5%"
 625 ><A
 626 NAME="FTN.AEN6"
 627 HREF="#AEN6"
 628 ><SPAN
 629 CLASS="footnote"
 630 >[1]</SPAN
 631 ></A
 632 ></TD
 633 ><TD
 634 ALIGN="LEFT"
 635 VALIGN="TOP"
 636 WIDTH="95%"
 637 ><FONT
 638 COLOR="RED"
 639 >bjk@luxsci.net</FONT
 640 ></TD
 641 ></TR
 642 ><TR
 643 ><TD
 644 ALIGN="LEFT"
 645 VALIGN="TOP"
 646 WIDTH="5%"
 647 ><A
 648 NAME="FTN.AEN12"
 649 HREF="#AEN12"
 650 ><SPAN
 651 CLASS="footnote"
 652 >[2]</SPAN
 653 ></A
 654 ></TD
 655 ><TD
 656 ALIGN="LEFT"
 657 VALIGN="TOP"
 658 WIDTH="95%"
 659 ><FONT
 660 COLOR="RED"
 661 >http://libpwmd.sourceforge.net/</FONT
 662 ></TD
 663 ></TR
 664 ><TR
 665 ><TD
 666 ALIGN="LEFT"
 667 VALIGN="TOP"
 668 WIDTH="5%"
 669 ><A
 670 NAME="FTN.AEN15"
 671 HREF="#AEN15"
 672 ><SPAN
 673 CLASS="footnote"
 674 >[3]</SPAN
 675 ></A
 676 ></TD
 677 ><TD
 678 ALIGN="LEFT"
 679 VALIGN="TOP"
 680 WIDTH="95%"
 681 ><FONT
 682 COLOR="RED"
 683 >http://pwmd.sourceforge.net/</FONT
 684 ></TD
 685 ></TR
 686 ><TR
 687 ><TD
 688 ALIGN="LEFT"
 689 VALIGN="TOP"
 690 WIDTH="5%"
 691 ><A
 692 NAME="FTN.AEN51"
 693 HREF="#AEN51"
 694 ><SPAN
 695 CLASS="footnote"
 696 >[4]</SPAN
 697 ></A
 698 ></TD
 699 ><TD
 700 ALIGN="LEFT"
 701 VALIGN="TOP"
 702 WIDTH="95%"
 703 ><FONT
 704 COLOR="RED"
 705 >http://qpwmc.sourceforge.net/</FONT
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