doc/homework/storage.html - view

File: [LON-CAPA] / doc / homework / storage.html
Revision 1.3: download - view: text, annotated - select for diffs
Thu Apr 7 06:56:20 2005 UTC (19 years, 1 month ago) by albertel
Branches: MAIN
CVS tags: version_2_9_X, version_2_9_99_0, version_2_9_1, version_2_9_0, version_2_8_X, version_2_8_99_1, version_2_8_99_0, version_2_8_2, version_2_8_1, version_2_8_0, version_2_7_X, version_2_7_99_1, version_2_7_99_0, version_2_7_1, version_2_7_0, version_2_6_X, version_2_6_99_1, version_2_6_99_0, version_2_6_3, version_2_6_2, version_2_6_1, version_2_6_0, version_2_5_X, version_2_5_99_1, version_2_5_99_0, version_2_5_2, version_2_5_1, version_2_5_0, version_2_4_X, version_2_4_99_0, version_2_4_2, version_2_4_1, version_2_4_0, version_2_3_X, version_2_3_99_0, version_2_3_2, version_2_3_1, version_2_3_0, version_2_2_X, version_2_2_99_1, version_2_2_99_0, version_2_2_2, version_2_2_1, version_2_2_0, version_2_1_X, version_2_1_99_3, version_2_1_99_2, version_2_1_99_1, version_2_1_99_0, version_2_1_3, version_2_1_2, version_2_1_1, version_2_1_0, version_2_12_X, version_2_11_X, version_2_11_4_uiuc, version_2_11_4_msu, version_2_11_4, version_2_11_3_uiuc, version_2_11_3_msu, version_2_11_3, version_2_11_2_uiuc, version_2_11_2_msu, version_2_11_2_educog, version_2_11_2, version_2_11_1, version_2_11_0_RC3, version_2_11_0_RC2, version_2_11_0_RC1, version_2_11_0, version_2_10_X, version_2_10_1, version_2_10_0_RC2, version_2_10_0_RC1, version_2_10_0, version_2_0_X, version_2_0_99_1, version_2_0_2, version_2_0_1, version_2_0_0, version_1_99_3, version_1_99_2, version_1_99_1_tmcc, version_1_99_1, version_1_99_0_tmcc, version_1_99_0, loncapaMITrelate_1, language_hyphenation_merge, language_hyphenation, bz6209-base, bz6209, HEAD, GCI_3, GCI_2, GCI_1, BZ4492-merge, BZ4492-feature_horizontal_radioresponse, BZ4492-feature_Support_horizontal_radioresponse, BZ4492-Support_horizontal_radioresponse

- ENV -> env

1: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 2: <html> 3: <head> 4: <title>Store / Restore</title> 5: </head> 6: 7: <body> 8: <h1>Store / Restore</h1> 9: 10: 11: 2 important functions in lonnet.pm are 12: <tt>&Apache::lonnet::store()</tt> and 13: <tt>&Apache::lonnet:restore()</tt>. These functions are for 14: handlers to store a perl hash to a users permanent data space in 15: an easy manner, and to retrieve it again on another call. It is 16: expected that a handler would use this once at the begining to 17: retrieve data. And then once at the end to send only the new 18: data back. 19: 20: 21: The hash that is returned by <tt>restore</tt> will have all of 22: the previous value for all of the elments of the hash. 23: 24: 25: Example: 26: 27: <pre> 28: #creating a hash 29: my %hash; 30: $hash{'foo'}='bar'; 31: #storing it 32: &Apache::lonnet::store(\%hash); 33: #changing a value 34: $hash{'foo'}='notbar'; 35: #adding a new value 36: $hash{'bar'}='foo'; 37: &Apache::lonnet::store(\%hash); 38: #retrieving the hash 39: my %history=&Apache::lonnet::restore(); 40: #print the hash 41: foreach my $key (sort(keys(%history))) { 42: print("\%history{$key} = $history{$key}"); 43: } 44: </pre> 45: Will print out: 46: <pre> 47: %history{1:foo} = bar 48: %history{1:keys} = foo:timestamp 49: %history{1:timestamp} = 990455579 50: %history{2:bar} = foo 51: %history{2:foo} = notbar 52: %history{2:keys} = foo:bar:timestamp 53: %history{2:timestamp} = 990455580 54: %history{bar} = foo 55: %history{foo} = notbar 56: %history{timestamp} = 990455580 57: %history{version} = 2 58: </pre> 59: 60: Note that the special hash entries keys, version 61: and timestamp were added to the hash. version will 62: be equal to the total number of versions of the data that have 63: been stored. The timestamp attribute will be the UNIX 64: time the hash was stored. keys is available in every 65: historical section to list which keys were added or changed 66: at a specific historical revision of a hash. 67: 68: 69: Warning do not store the hash that restore returns 70: directly. This will cause a mess since it will restore the 71: historical keys as if the were new keys. I.E. <tt>1:foo</tt> 72: will become <tt>1:1:foo</tt> etc. 73: 74: <h3> 75: Calling convention: 76: </h3> 77: <pre> 78: my %record=&Apache::lonnet::restore($symb,$courseid,$domain,$uname); 79: &Apache::lonnet::store(\%newrecord,$symb,$courseid,$domain,$uname); 80: </pre> 81: <h4> 82: Arguments (only %newrecord is required the rest are somewhat 83: optional, read the details): 84: </h4> 85: <ul> 86: <li> 87: $symb - a string containing the internal name of the 88: specific instance of a resource. Usually this value can be 89: gotten from 90: <tt>&Apache::lonnet::symbread($filename)</tt>. If the 91: argument is blank, it will attempt to use <tt>symbread()</tt> 92: for it. If the result is ambiguous store/restore will fail. 93: </li> 94: <li> 95: $courseid - the internal name for a course, usually 96: found in <tt>$env{'request.course.id'}</tt> which is what will 97: be looked at if no value is passed to the functions. 98: </li> 99: <li> 100: $domain - the domain that the user belongs to, usually 101: found in <tt>$env{'user.domain'}</tt> which is what will be 102: looked at if no value is passed to the functions. 103: </li> 104: <li> 105: $uname - the login name for the user, usually 106: found in <tt>$env{'user.name'}</tt> which is what will 107: be looked at if no value is passed to the functions. 108: </li> 109: <li> 110: \%newrecord - the hash to store being passed by reference 111: </li> 112: </ul> 113: <h4> 114: Return values: 115: </h4> 116: <ul> 117: <li> 118: an empty string - the function was unable to determine 119: exactly where to store or restore from. At least one of the 120: "optional" arguments was unable to be determined. 121: </li> 122: <li> 123: a hash - restore successfully read a old hash for this 124: specific user / resource instance. 125: </li> 126: <li> 127: no_such_host - the homeserver dosen't exist 128: in the network. 129: </li> 130: <li> 131: con_delayed - the homeserver was uncontactable at 132: this time. The store will be delayed until it is again 133: available. 134: </li> 135: <li> 136: con_failed - the homeserver was uncontactable at this 137: time and store was unable to delay the store until a later 138: time. The store failed. 139: </li> 140: <li> 141: ok - the store completed succesfully 142: </li> 143: <li> 144: error: - remote server failied to store or restore the 145: reason follows the : 146: </li> 147: </ul> 148: <hr> 149: <address><a href="mailto:albertel@marvin.lite.msu.edu">Guy Albertelli</a></address> 150:  151:  152: Last modified: Wed May 30 10:52:16 EDT 2001 153:  154: </body> 155: </html>

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