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<h2><a name="_Toc421867053">Session Three: Roles and lonnet/loncommon useful
functions (Guy)</a></h2>
<h3><a name=name></a><a name="_Toc421867054">NAME</a></h3>
<p>Apache::lonnet - Subroutines to ask questions about things in the network.</p>
<div align=center style='text-align:center'>
<hr size=2 width="100%" align=center>
</div>
<h3><a name=synopsis></a><a name="_Toc421867055">SYNOPSIS</a></h3>
<p>Invoked by other LON-CAPA modules, when they need to talk to or about objects
in the network.</p>
<pre> &Apache::lonnet::SUBROUTINENAME(ARGUMENTS);</pre>
<p>Common parameters:</p>
<ul type=disc>
<li>$uname : an internal username (if $cname expecting a course Id specifically)
</li>
<li>$udom : a domain (if $cdom expecting a course's domain specifically) </li>
<li>$symb : a resource instance identifier </li>
<li>$namespace : the name of a .db file that contains the data needed or being
set. </li>
</ul>
<div align=center style='text-align:center'>
<hr size=2 width="100%" align=center>
</div>
<h3><a name=introduction></a><a name="_Toc421867056">INTRODUCTION</a></h3>
<p>This module provides subroutines which interact with the lonc/lond (TCP)
network layer of LON-CAPA. And Can be used to ask about - classes - users
- resources</p>
<p>For many of these objects you can also use this to store data about them
or modify them in various ways.</p>
<p>This is part of the LearningOnline Network with CAPA project described at
<a
href="http://www.lon-capa.org./">http://www.lon-capa.org.</a></p>
<div align=center style='text-align:center'>
<hr size=2 width="100%" align=center>
</div>
<h3><a name="return_messages"></a><a name="_Toc421867057">RETURN MESSAGES</a></h3>
<ul type=disc>
<li>con_lost : unable to contact remote host </li>
<li>con_delayed : unable to contact remote host, message will be delivered
when the connection is brought back up </li>
<li>con_failed : unable to contact remote host and unable to save message
for later delivery </li>
<li>error: : an error a occured, a description of the error follows the :
</li>
<li>no_such_host : unable to fund a host associated with the user/domain that
was requested </li>
</ul>
<div align=center style='text-align:center'>
<hr size=2 width="100%" align=center>
</div>
<h3><a name="session_environment_functions"></a><a name="_Toc421867058">Session
Environment Functions</a></h3>
<ul type=disc>
<li><code><span style='font-family:
Courier'>appenv(%hash)</span></code> : the value of %hash is written to the
user envirnoment file, and will be restored for each access this user makes
during this session, also modifies the %ENV for the current process </li>
<li><code><span style='font-family:
Courier'>delenv($regexp)</span></code> : removes all items from the session
environment file that matches the regular expression in $regexp. The values
are also delted from the current processes %ENV. </li>
</ul>
<h3><a name="user_information"></a><a name="_Toc421867059">User Information</a></h3>
<ul type=disc>
<li><code><span style='font-family:
Courier'>queryauthenticate($uname,$udom)</span></code> : try to determine
user's current authentication scheme </li>
<li><code><span style='font-family:
Courier'>authenticate($uname,$upass,$udom)</span></code> : try to authenticate
user from domain's lib servers (first use the current one), $upass should
be the users password </li>
<li><code><span style='font-family:
Courier'>homeserver($uname,$udom)</span></code> : find the server which has
the user's directory and files (there must be only one) . This caches the
answer and also caches if there is an error.</li>
<li><code><span style='font-family:
Courier'>idget($udom,@ids)</span></code> : find the usernames behind a list
of IDs (IDs are a unique resource in a domain, there must be only 1 ID per
username, and only 1 username per ID in a specific domain) (returns hash:
id=>name,id=>name) </li>
<li><code><span style='font-family:
Courier'>idrget($udom,@unames)</span></code> : find the IDs behind a list
of usernames (returns hash: name=>id,name=>id) </li>
<li><code><span style='font-family:
Courier'>idput($udom,%ids)</span></code> : store away a list of names and
associated IDs </li>
<li><code><span style='font-family:
Courier'>rolesinit($udom,$username,$authhost)</span></code> : get user privileges
</li>
<li><code><span style='font-family:
Courier'>usection($udom,$uname,$cname)</span></code> : finds the section
of student in the course $cname, return section name/number or '' for ``not
in course'' and '-1' for ``no section'' </li>
<li><code><span style='font-family:
Courier'>userenvironment($udom,$uname,@what)</span></code> : gets the values
of the keys passed in @what from the requested user's environment, returns
a hash </li>
</ul>
<h3><a name="user_roles"></a><a name="_Toc421867060">User Roles</a></h3>
<ul type=disc>
<li><code><span style='font-family:
Courier'>allowed($priv,$uri)</span></code> : check for a user privilege;
returns codes for allowed actions F: full access U,I,K: authentication modes
(cxx only) '': forbidden 1: user needs to choose course 2: browse allowed
</li>
<li><code><span style='font-family:
Courier'>definerole($rolename,$sysrole,$domrole,$courole)</span></code> :
define role; define a custom role rolename set privileges in format of lonTabs/roles.tab
for system, domain, and course level </li>
<li><code><span style='font-family:
Courier'>plaintext($short)</span></code> : return value in %prp hash (rolesplain.tab);
plain text explanation of a user role term </li>
</ul>
<h3><a name="user_modification"></a><a name="_Toc421867061">User Modification</a></h3>
<ul type=disc>
<li><code><span
style='font-family:Courier'>assignrole($udom,$uname,$url,$role,$end,$start)</span></code>
: assign role; give a role to a user for the level given by URL. Optional
start and end dates (leave empty string or zero for ``no date'') </li>
<li><span style='font-family:
"Courier New"'>changepass($uname,$udom,$currentpass,$newpass,$server):</span>
attempts to change a users, password, possible return values are: <span
style='font-family:"Courier New"'>ok, pwchange_failure, non_authorized, auth_mode_error,
unknown_user, refused</span></li>
<li><code><span
style='font-family:Courier'>modifyuserauth($udom,$uname,$umode,$upass)</span></code>
: modify user authentication </li>
<li><code><span
style='font-family:Courier'>modifyuser($udom,$uname,$uid,$umode,$upass,$first,$middle,$last,$gene)</span></code>
: modify user </li>
<li>modifystudent($udom,$uname,$uid,$umode,$upass,$first,$middle,$last,$gene,$usec,
$end,$start) : modify student </li>
<li><code><span
style='font-family:Courier'>assigncustomrole($udom,$uname,$url,$rdom,$rnam,$rolename,$end,$start)</span></code>
: assign custom role; give a custom role to a user for the level given by
URL. Specify name and domain of role author, and role name </li>
<li><code><span
style='font-family:Courier'>revokerole($udom,$uname,$url,$role)</span></code>
: revoke a role for url </li>
<li><code><span
style='font-family:Courier'>revokecustomrole($udom,$uname,$url,$role)</span></code>
: revoke a custom role </li>
</ul>
<h3><a name="course_infomation"></a><a name="_Toc421867062">Course Infomation</a></h3>
<ul type=disc>
<li><code><span style='font-family:
Courier'>coursedescription($courseid)</span></code> : course description
</li>
<li><span style='font-family:
"Courier New"'>courseresdata($coursenum,$coursedomain,@which) :</span> request
for current parameter setting for a specific course, @what should be a list
of parameters to ask about. This routine caches answers for 5 minutes.</li>
</ul>
<h3><a name="course_modification"></a><a name="_Toc421867063">Course Modification</a></h3>
<ul type=disc>
<li><code><span
style='font-family:Courier'>writecoursepref($courseid,%prefs)</span></code>
: write preferences (environment database) for a course </li>
<li><code><span
style='font-family:Courier'>createcourse($udom,$description,$url)</span></code>
: make/modify course </li>
</ul>
<h3><a name="resource_subroutines"></a><a name="_Toc421867064">Resource Subroutines</a></h3>
<ul type=disc>
<li><code><span style='font-family:
Courier'>subscribe($fname)</span></code> : subscribe to a resource, returns
URL if possible (probably should use repcopy instead) </li>
<li><code><span style='font-family:
Courier'>repcopy($filename)</span></code> : subscribes to the requested file,
and attempts to replicate from the owning library server, Might return HTTP_SERVICE_UNAVAILABLE,
HTTP_NOT_FOUND, FORBIDDEN, OK, or HTTP_BAD_REQUEST, also attempts to grab
the metadata for the resource. Expects the local filesystem pathname (/home/httpd/html/res/....)
</li>
</ul>
<h3><a name="resource_information"></a><a name="_Toc421867065">Resource Information</a></h3>
<ul type=disc>
<li>EXT($varname,$symb,$udom, $uname) : evaluates and returns the value of
a vairety of different possible values, $varname should be a request string,
and the other parameters can be used to specify who and what one is asking
about. </li>
</ul>
<p><span style='font-size:10.0pt'>Possible values for $varname are environment.lastname
(or other item from the environment hash), user.name (or someother aspect
about the user), resource.0.maxtries (or some other part and parameter of
a resource)</span></p>
<ul type=disc>
<li><code><span
style='font-family:Courier'>directcondval($number)</span></code> : get current
value of a condition; reads from a state string </li>
<li><code><span
style='font-family:Courier'>condval($condidx)</span></code> : value of condition
index based on state </li>
<li><code><span
style='font-family:Courier'>metadata($uri,$what,$liburi,$prefix,$depthcount)</span></code>
: request a resource's metadata, $what should be either a specific key,
or either 'keys' (to get a list of possible keys) or 'packages' to get a
list of packages that this resource currently uses, the last 3 arguments
are only used internally for recursive metadata. This function automatically
caches all requests</li>
<li><code><span
style='font-family:Courier'>metadata_query($query,$custom,$customshow)</span></code>
: make a metadata query against the network of library servers; returns
file handle of where SQL and regex results will be stored for query</li>
<li><code><span
style='font-family:Courier'>symbread($filename)</span></code> : return symbolic
list entry (filename argument optional); returns the data handle </li>
<li><span style='font-family:
"Courier New"'>symbverify($symb,$thisfn):</span> verifies that $symb actually
exists and is a possible symb for the URL in $thisfn, returns a 1 on success,
0 on failure, user must be in a course, as it assumes the existance of the
course init hash, and uses $ENV('request.course.id'}</li>
<li><span style='font-family:
"Courier New"'>symbclean($symb):</span> removes versions numbers from a symb,
returns the cleaned symb</li>
<li><span style='font-family:
"Courier New"'>is_on_map($uri) :</span> checks if the $uri is somewhere on
the current course map, user must be in a course for it to work</li>
<li><code><span
style='font-family:Courier'>numval($salt)</span></code> : return random seed
value (addend for rndseed) </li>
<li><code><span
style='font-family:Courier'>rndseed($symb,$courseid,$udom,$username)</span></code>
: create a random sum; returns a random seed, all arguments are optional,
if they aren't sent it uses the environment to derive them. Note: if symb
isn't sent and it can't get one from &symbread it will use the current
time as its return value </li>
<li><code><span
style='font-family:Courier'>ireceipt($funame,$fudom,$fucourseid,$fusymb)</span></code>
: return unique, unfakeable, receipt </li>
<li><code><span
style='font-family:Courier'>receipt()</span></code> : API to ireceipt working
off of ENV values; given out to users </li>
<li><code><span
style='font-family:Courier'>countacc($url)</span></code> : count the number
of accesses to a given URL </li>
<li><code><span
style='font-family:Courier'>checkout($symb,$tuname,$tudom,$tcrsid)</span></code>
: creates a record of a user having looked at an item, most likely printed
out or otherwise using a resource </li>
<li><code><span
style='font-family:Courier'>checkin($token)</span></code> : updates that
a resource has beeen returned (a hard copy version for instance) and returns
the data that $token was Checkout with ($symb, $tuname, $tudom, and $tcrsid)
</li>
<li><code><span
style='font-family:Courier'>expirespread($uname,$udom,$stype,$usymb)</span></code>
: set expire date for spreadsheet </li>
<li><code><span
style='font-family:Courier'>devalidate($symb)</span></code> : devalidate
temporary spreadsheet calculations, forcing spreadsheet to reevaluate the
resource scores next time. </li>
</ul>
<h3><a name="storing/retreiving_data"></a><a name="_Toc421867066"><span
style='"storing\/retreiving_data"'>Storing/Retrieving Data</span></a></h3>
<ul type=disc>
<li><code><span
style='font-family:Courier'>store($storehash,$symb,$namespace,$udom,$uname)</span></code>
: stores hash permanently for this url; hashref needs to be given and should
be a \%hashname; the remaining args aren't required and if they aren't passed
or are '' they will be derived from the ENV </li>
<li><code><span
style='font-family:Courier'>cstore($storehash,$symb,$namespace,$udom,$uname)</span></code>
: same as store but uses critical subroutine </li>
<li><code><span
style='font-family:Courier'>restore($symb,$namespace,$udom,$uname)</span></code>
: returns hash for this symb; all args are optional </li>
<li><code><span
style='font-family:Courier'>tmpstore($storehash,$symb,$namespace,$udom,$uname)</span></code>
: storage that works very similar to store/cstore, but all data is stored
in a temporary location and can be reset using tmpreset, $storehash should
be a hash reference, returns nothing on success </li>
<li><code><span
style='font-family:Courier'>tmprestore($symb,$namespace,$udom,$uname)</span></code>
: storage that works very similar to restore, but all data is stored in
a temporary location and can be reset using tmpreset. Returns a hash of
values on success, error string otherwise. </li>
<li><code><span
style='font-family:Courier'>tmpreset($symb,$namespace,$udom,$uname)</span></code>
: temporary storage reset, deltes all keys for $symb form the temporary
storage hash. </li>
<li><code><span
style='font-family:Courier'>get($namespace,$storearr,$udom,$uname)</span></code>
: returns hash with keys from array reference filled in from namesp ($udomain
and $uname are optional) </li>
<li><code><span
style='font-family:Courier'>del($namespace,$storearr,$udom,$uname)</span></code>
: deletes keys out of array from namesp ($udomain and $uname are optional)
</li>
<li><code><span
style='font-family:Courier'>dump($namespace,$udom,$uname,$regexp)</span></code>
: dumps the complete (or key matching regexp) namespace into a hash ($udomain,
$uname and $regexp are optional) </li>
<li><code><span
style='font-family:Courier'>put($namespace,$storehash,$udomain,$uname)</span></code>
: stores hash in namesp ($udomain and $uname are optional) </li>
<li><code><span
style='font-family:Courier'>cput($namespace,$storehash,$udomain,$uname)</span></code>
: critical put ($udomain and $uname are optional) </li>
<li><code><span
style='font-family:Courier'>eget($namespace,$storearr,$udomain,$uname)</span></code>
: returns hash with keys from array reference filled in from namesp (encrypts
the return communication) ($udomain and $uname are optional) </li>
<li><code><span
style='font-family:Courier'>log($udom,$name,$home,$message)</span></code>
: write to permanent log for user; use critical subroutine </li>
</ul>
<h3><a name="network_status_functions"></a><a name="_Toc421867067">Network Status
Functions</a></h3>
<ul type=disc>
<li><code><span
style='font-family:Courier'>dirlist($uri)</span></code> : return directory
list based on URI </li>
<li><code><span
style='font-family:Courier'>spareserver()</span></code> : find server with
least workload from spare.tab </li>
</ul>
<h3><a name="apache_request"></a><a name="_Toc421867068">Apache Request</a></h3>
<ul type=disc>
<li><code><span
style='font-family:Courier'>ssi($url,%hash)</span></code> : server side include,
does a complete request cycle on url to localhost, posts hash </li>
</ul>
<h3><a name="data_to_string_to_data"></a><a name="_Toc421867069">Data to String
to Data</a></h3>
<ul type=disc>
<li><code><span
style='font-family:Courier'>hash2str(%hash)</span></code> : convert a hash
into a string complete with escaping and '=' and '&' separators, supports
elements that are arrayrefs and hashrefs </li>
<li><code><span
style='font-family:Courier'>hashref2str($hashref)</span></code> : convert
a hashref into a string complete with escaping and '=' and '&' separators,
supports elements that are arrayrefs and hashrefs </li>
<li><code><span
style='font-family:Courier'>arrayref2str($arrayref)</span></code> : convert
an arrayref into a string complete with escaping and '&' separators,
supports elements that are arrayrefs and hashrefs </li>
<li><code><span
style='font-family:Courier'>str2hash($string)</span></code> : convert string
to hash using unescaping and splitting on '=' and '&', supports elements
that are arrayrefs and hashrefs </li>
<li><code><span
style='font-family:Courier'>str2array($string)</span></code> : convert string
to hash using unescaping and splitting on '&', supports elements that
are arrayrefs and hashrefs </li>
</ul>
<h3><a name="logging_routines"></a><a name="_Toc421867070">Logging Routines</a></h3>
<p>These routines allow one to make log messages in the lonnet.log and lonnet.perm
logfiles.</p>
<ul type=disc>
<li><code><span
style='font-family:Courier'>logtouch()</span></code> : make sure the logfile,
lonnet.log, exists </li>
<li><code><span
style='font-family:Courier'>logthis()</span></code> : append message to the
normal lonnet.log file, it gets preiodically rolled over and deleted. </li>
<li><code><span
style='font-family:Courier'>logperm()</span></code> : append a permanent
message to lonnet.perm.log, this log file never gets deleted by any automated
portion of the system, only messages of critical importance should go in
here. </li>
</ul>
<h3><a name="general_helper_routines"></a><a name="_Toc421867071">General File
Helper Routines</a></h3>
<ul type=disc>
<li><code><span
style='font-family:Courier'>getfile($file)</span></code> : serves up a file,
returns the contents of a file or -1; replicates and subscribes to the file
</li>
<li><code><span
style='font-family:Courier'>filelocation($dir,$file)</span></code> : returns
file system location of a file based on URI; meant to be ``fairly clean''
absolute reference, $dir is a directory that relative $file lookups are
to looked in ($dir of /a/dir and a file of ../bob will become /a/bob) </li>
<li><code><span
style='font-family:Courier'>hreflocation($dir,$file)</span></code> : returns
file system location or a URL; same as filelocation except for hrefs </li>
<li><code><span
style='font-family:Courier'>declutter()</span></code> : declutters URLs (remove
docroot, beginning slashes, 'res' etc) </li>
</ul>
<h3><a name="_Toc421867072">HTTP Helper Routines</a></h3>
<ul type=disc>
<li><code><span
style='font-family:Courier'>escape()</span></code> : unpack non-word characters
into CGI-compatible hex codes </li>
<li><code><span
style='font-family:Courier'>unescape()</span></code> : pack CGI-compatible
hex codes into actual non-word ASCII character </li>
</ul>
</div>
<h1> </h1>
<h3><a name="underlying_communication_routines_(shoul"></a><a
name="_Toc421867073">Private: Underlying communication routines (Shouldn't call)</a></h3>
<ul type=disc>
<li><code><span style='font-family:
Courier'>subreply()</span></code> : tries to pass a message to lonc, returns
con_lost if incapable </li>
<li><code><span style='font-family:
Courier'>reply()</span></code> : uses subreply to send a message to remote
machine, logs all failures </li>
<li><code><span style='font-family:
Courier'>critical()</span></code> : passes a critical message to another
server; if cannot get through then place message in connection buffer directory
and returns con_delayed, if incapable of saving message, returns con_failed
</li>
<li><code><span style='font-family:
Courier'>reconlonc()</span></code> : tries to reconnect lonc client processes.
</li>
</ul>
<h3><a name="resource_access_logging"></a><a name="_Toc421867074">Private: Resource
Access Logging</a></h3>
<ul type=disc>
<li><code><span style='font-family:
Courier'>flushcourselogs()</span></code> : flush (save) buffer logs and access
logs </li>
<li><code><span style='font-family:
Courier'>courselog($what)</span></code> : save message for course in hash
</li>
<li><code><span style='font-family:
Courier'>courseacclog($what)</span></code> : save message for course using
&courselog(). Perform special processing for specific resource types (problems,
exams, quizzes, etc). </li>
<li><code><span style='font-family:
Courier'>goodbye()</span></code> : flush course logs and log shutting down;
it is called in srm.conf as a PerlChildExitHandler </li>
</ul>
<h3><a name=other></a><a name="_Toc421867075">Private: Other</a></h3>
<p><code><span style='font-family:"Courier New"'>symblist($mapname,%newhash)</span></code><span
style='font-family:"Courier New"'> :</span> update symbolic storage links </p>
<h3><a name="_Toc421867076">Coding Guidelines</a></h3>
<p class=H5><span style='layout-grid-mode:
both'>Things to keep in mind while coding handlers for LON-CAPA </span></p>
<p><span
style='font-size:14.0pt'>1.<span style='font:7.0pt "Times New Roman"'>
</span></span><span style='font-size:14.0pt'>DON'T write to Access machine disks
with permanent data, use store/restore </span></p>
<p><span
style='font-size:14.0pt'>2.<span style='font:7.0pt "Times New Roman"'>
</span></span><span style='font-size:14.0pt'>DON'T </span><span
style='font-size:14.0pt;font-family:"Courier New"'>use print()</span><span
style='font-size:14.0pt'>, use </span><span style='font-size:14.0pt;font-family:
"Courier New"'>$request->print()</span><span style='font-size:14.0pt'> </span></p>
<p><span
style='font-size:14.0pt'>3.<span style='font:7.0pt "Times New Roman"'>
</span></span><span style='font-size:14.0pt'>DON'T launch children </span></p>
<p><span
style='font-size:14.0pt'>4.<span style='font:7.0pt "Times New Roman"'>
</span></span><span style='font-size:14.0pt'>DO use </span><span
style='font-size:14.0pt;font-family:"Courier New"'>$Apache::lonnet::perlvar{'lonDaemons'}/tmp</span><span
style='font-size:14.0pt'> for temporary data. </span></p>
<p><span
style='font-size:14.0pt'>5.<span style='font:7.0pt "Times New Roman"'>
</span></span><span style='font-size:14.0pt'>DO query the return value of every
file operation. </span></p>
<p><span
style='font-size:14.0pt'>6.<span style='font:7.0pt "Times New Roman"'>
</span></span><span style='font-size:14.0pt'>DO </span><span style='font-size:
14.0pt;font-family:"Courier New"'>use strict;</span><span style='font-size:
14.0pt'> </span></p>
<p><span
style='font-size:14.0pt'>7.<span style='font:7.0pt "Times New Roman"'>
</span></span><span style='font-size:14.0pt'>DO </span><span style='font-size:
14.0pt;font-family:"Courier New"'>use strict;</span><span style='font-size:
14.0pt'> </span></p>
<p><span
style='font-size:14.0pt'>8.<span style='font:7.0pt "Times New Roman"'>
</span></span><span style='font-size:14.0pt'>DO familiarize your self with the
functions in </span><span style='font-size:14.0pt;font-family:"Courier New"'>lonnet.pm</span><span
style='font-size:14.0pt'> and use them to communicate with other servers and when
you handler needs to ask questions. </span></p>
<p>9.<span
style='font:7.0pt "Times New Roman"'> </span><span
style='font-size:14.0pt'>DON'T use </span><span style='font-size:14.0pt;
font-family:"Courier New"'>&Apache::lonnet::reply()</span><span
style='font-size:14.0pt'> </span></p>
<br
clear=ALL style='page-break-before:always;'>
<div class=Section2> </div>
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