ug_ch12.htm

db.* (pronounced dee-be star) is an advanced, high performance, small footprint embedded database fo

edit <i>{</i>own | prev | next<i>}</i> <i>setname</i>
edit dba
edit opt
edit <i>{</i>dchain | nextslot<i>}</i>
edit hex</font>
</pre>
<h3><a name="RecordTypes" id="RecordTypes"></a>12.5.1 Editing
Record Types</h3>
<p><font size="2">The <b>edit type</b> command allows you to alter
the record type identification number. The current type is printed
(both numerically and symbolically). The new record type may be
entered as a number or name. All subsequent displays and
interpretations of the current record are based on the new type.
The record type must be one that is included in the current file,
or the display command is unable to display the record.</font></p>
<p>The record type may contain an embedded record lock bit (RLB).
The bit will show in the numeric display as a 40 in the high-order
byte of the record type. Textually, the notation "<b>- RLB</b>"
will appear following the name of the record type. The RLB may be
cleared by entering a new (or the same) record type. It may be set
by entering 40 as the high-order byte of the type.</p>
<h3><a name="Pointers" id="Pointers"></a>12.5.2 Editing Set and
Member Pointers</h3>
<p><font size="2">Individual parts of the set and member pointers
may be edited by naming the part (for example, <b>count</b> or
<b>next</b>) and set name, <i>setname</i>.</font></p>
<p>The current value is displayed. The new value may be entered in
the standard database address format as shown in the following
example:</p>
<pre>
<font color="#0000FF">dbedit&gt; edit first author_list
Current value is [1:15]
New value? 1:18
dbedit&gt; </font>
</pre>
<p><font size="2">If no change is desired, simply press
&lt;Enter&gt;.</font></p>
<h3><a name="Address" id="Address"></a>12.5.3 Editing the Database
Address</h3>
<p><font size="2">The database address portion of a record (bytes
2-5) may be edited using the <b>edit dba</b> command. The existing
database address value is printed. The new value may be entered in
standard database address format.</font></p>
<p>If the current record slot is a deleted record, the database
address portion contains the slot number of the next slot on the
delete chain. Because this is not a database address but a slot
number, edits to delete chain entries should be specified with file
number 0 (for example, <b>0:25</b>).</p>
<h3><a name="Optional" id="Optional"></a>12.5.4 Editing the
Optional Key Bits</h3>
<p><font size="2">When an optional key is stored, a bit is set in
the data record to represent its presence in the key file. These
bits may be changed using the <b>edit opt</b> edit command. The bit
map (in hexadecimal) is displayed together with the names of all
optional keys in the record type. Beside each key name is a
notation indicating whether the key is stored<br>
(- STORED) or not (- NOT STORED):</font></p>
<pre>
<font color="#0000FF">dbedit&gt; edit opt
40                      
PUBLISHER - NOT STORED
INFO_TYPE - STORED
New value?publisher,info_type</font>
</pre>
<p><font size="2">The new value may be entered as a bit map (in
hexadecimal), or as a list of the key names (comma separated) that
are to be set. Note that any changes performed here will require
the use of <b>keybuild</b> in order to make the data files
consistent with the key files. In the above example, both the
<b>publisher</b> and <b>info_type</b> optional key flags will be
set.</font></p>
<h3><a name="PageZero" id="PageZero"></a>12.5.5 Editing Page
Zero</h3>
<p><font size="2">The first two long integers in page zero of the
current file (the file containing the current record) may be edited
using the <b>edit dchain</b> and <b>edit nextslot</b> commands.
Both of these commands display the current value and prompt for the
new one. They are written to the file immediately. Note that the
values are slot numbers, not database addresses, and do not take
file numbers.</font></p>
<h3><a name="Hexadecimal" id="Hexadecimal"></a>12.5.6 General
Hexadecimal Editing</h3>
<p><font size="2">To allow the operator to make changes to the
database not covered in other commands, <b>dbedit</b> provides the
ability to edit a file as a stream of hexadecimal bytes. In this
mode you can:</font></p>
<p><font face="Symbol" size="2">&middot;</font> <font size=
"2">Display any number of lines in both hexadecimal and
ASCII<br></font><font face="Symbol" size="2">&middot;</font>
<font size="2">Move to any byte position in the
file<br></font><font face="Symbol" size="2">&middot;</font>
<font size="2">Search forward and backward for a
pattern<br></font><font face="Symbol" size="2">&middot;</font>
<font size="2">Replace characters on a byte-for-byte basis in
either hexadecimal or ASCII</font></p>
<p>The hexadecimal editing mode is initiated by entering the
<b>edit hex</b> command. When in this mode, the prompt is changed
to:</p>
<pre>
<font color="#0000FF">hex&gt; </font>
</pre>
<p><font size="2">To exit the hexadecimal edit mode, enter the
command:</font></p>
<pre>
<font color="#0000FF">hex&gt; end
dbedit&gt; </font>
</pre>
<p><font size="2">When hexadecimal edit mode is entered, changes
that were made to the current record are written to the database,
and the current position in the file becomes the file address of
the current record. The changes made in hexadecimal edit mode are
written to the database by the <b>end</b> command. To cancel the
changes and return to <b>dbedit</b> mode, enter
<b>cancel</b>.</font></p>
<p>After ending hexadecimal edit mode, the current record is
returned to its original slot, unless the current file position
lies within a different record, in which case <b>dbedit</b> will
prompt you to see if your current record should be changed to this
new position, or if you want to return to the original current
record.</p>
<p>Table 12-1 describes the commands that can be used in hex edit
mode.</p>
<p align="center"><b>Table 12-1. Hex Mode Commands</b></p>
<table border="1" cellspacing="1" cellpadding="7" width="542">
<tr>
<td width="21%" valign="top">
<p><b><font size="2">Command</font></b></p>
</td>
<td width="79%" valign="top">
<p><b><font size="2">Definition</font></b></p>
</td>
</tr>
<tr>
<td width="21%" valign="top">
<p><b><font size="2">print <i>N</i></font></b></p>
</td>
<td width="79%" valign="top">
<p><font size="2">Print <b><i>N</i></b> lines (both hexadecimal and
ASCII representation). If <b><i>N</i></b> is absent, print one
line.</font></p>
</td>
</tr>
<tr>
<td width="21%" valign="top">
<p><b><font size="2">+<i>N</i></font></b></p>
</td>
<td width="79%" valign="top">
<p><font size="2">Move forward <b><i>N</i></b> characters. If
<b><i>N</i></b> is absent, move one character.</font></p>
</td>
</tr>
<tr>
<td width="21%" valign="top">
<p><b><font size="2">-<i>N</i></font></b></p>
</td>
<td width="79%" valign="top">
<p><font size="2">Move backward <b><i>N</i></b> characters. If
<b><i>N</i></b> is absent, move one character.</font></p>
</td>
</tr>
<tr>
<td width="21%" valign="top">
<p><b><font size="2">=<i>N</i></font></b></p>
</td>
<td width="79%" valign="top">
<p><font size="2">Move to address <b><i>N</i></b>, where
<b><i>N</i></b> is a hexadecimal number between 0 and
FFFFFFFF.</font></p>
</td>
</tr>
<tr>
<td width="21%" valign="top">
<p><b><font size="2">&gt;<i>N</i></font></b></p>
</td>
<td width="79%" valign="top">
<p><font size="2">Move forward <b><i>N</i></b> lines. If
<b><i>N</i></b> is absent, move one line.</font></p>
</td>
</tr>
<tr>
<td width="21%" valign="top">
<p><b><font size="2">&lt;<i>N</i></font></b></p>
</td>
<td width="79%" valign="top">
<p><font size="2">Move backward <b><i>N</i></b> lines. If
<b><i>N</i></b> is absent, move one line.</font></p>
</td>
</tr>
<tr>
<td width="21%" valign="top">
<p><b><font size="2">&gt;&gt;<i>STRING</i></font></b></p>
</td>
<td width="79%" valign="top">
<p><font size="2">Search forward for <b><i>STRING</i></b>.
<b><i>STRING</i></b> may be either an ASCII string within quotes
("string"), or hexadecimal bytes (73 74 72 69 6E 67).</font></p>
</td>
</tr>
<tr>
<td width="21%" valign="top">
<p><b><font size="2">&lt;&lt;<i>STRING</i></font></b></p>
</td>
<td width="79%" valign="top">
<p><font size="2">Search backward for
<b><i>STRING</i></b>.</font></p>
</td>
</tr>
<tr>
<td width="21%" valign="top">
<p><b><font size="2">write <i>STRING</i></font></b></p>
</td>
<td width="79%" valign="top">
<p><font size="2">Write <b><i>STRING</i></b> into current
position.</font></p>
</td>
</tr>
<tr>
<td width="21%" valign="top">
<p><b><font size="2">cancel</font></b></p>
</td>
<td width="79%" valign="top">
<p><font size="2">Erase all edits since entering hex edit
mode.</font></p>
</td>
</tr>
<tr>
<td width="21%" valign="top">
<p><b><font size="2">end</font></b></p>
</td>
<td width="79%" valign="top">
<p><font size="2">End hex edit mode.</font></p>
</td>
</tr>
<tr>
<td width="21%" valign="top">
<p><b><font size="2">help</font></b></p>
</td>
<td width="79%" valign="top">
<p><font size="2">Print a short list of these commands. Alias is
<b>?</b>.</font></p>
</td>
</tr>
</table>
<h2><a name="Diagnostics" id="Diagnostics"></a>12.6
Diagnostics</h2>
<p><font size="2">Illegal changes to a database will be screened,
whenever possible, before they are made. For example, if a record
type is changed to a type not contained in the current file, the
change will not be allowed (except in hexadecimal edit
mode).</font></p>
<p>Since <b>dbedit</b> allows updates to set instances, it will be
important to know if a change has corrected a problem in the chain
of database addresses forming the set instance. For this purpose,
the <b>verify</b> command can be used to traverse an entire set
instance to check owner, previous, next, first, and last pointer
consistency. It will perform a check similar to that done by the
<b>dbcheck</b> utility. The name of the set must be identified with
the follopwing command:</p>
<pre>
<font color="#0000FF">verify <i>setname</i></font>
</pre>
<h2><a name="Miscellaneous" id="Miscellaneous"></a>12.7
Miscellaneous</h2>
<p><font size="2">The <b>exit</b> command will end your
<b>dbedit</b> session. If the current record was modified, it is
written to the database before exiting.</font></p>
<p>The <b>reread</b> command causes the current record to be read
from the database. This has the effect of canceling any updates
made to the record in the buffer.</p>
<p>To eliminate the titles in the <b>display</b> output, the
<b>notitles</b> command can be issued. The resulting output is
shorter, but readable to the experienced operator. By default,
titles will be printed. The <b>titles</b> command can be used to
cancel the <b>notitles</b> command.</p>
<p>To eliminate the data fields in the <b>display</b> output, the
<b>nofields</b> command can be issued. The resulting output will
only contain the overhead information (record type, <b>DB_ADDR</b>,
set pointers, etc.). This can be useful when the data in the record
is correct, but there are problems with the overhead information.
By default, fields will be printed. The <b>fields</b> command may
be used to cancel the <b>nofields</b> command.</p>
<p>All database addresses and counts will be displayed in decimal
format unless otherwise requested. To change the display format,
the <b>base</b> command may be issued.</p>
<pre>
<font color="#0000FF">base<i> {</i>10 | 16<i>}</i></font>
</pre>
<p><font size="2">Only base 10 (decimal) and base 16 (hexadecimal)
are recognized.</font></p>
<p>Any editor command or keyword may be abbreviated to a
non-ambiguous set of characters. If more than the required number
of characters is entered as a command, they must correctly spell
the intended command. If an ambiguous set of characters is entered,
an error message is displayed stating that more characters must be
entered.</p>
<h2><a name="Summary" id="Summary"></a>12.8 Command Summary</h2>
<p><font size="2">A syntax summary for each of the <b>dbedit</b>
commands is shown in the table below.</font></p>
<pre>
<font color="#0000FF">base <i>{</i>10 | 16<i>}</i>
display <i>[</i>type | dba | ts | opt<i>]</i>
display <i>{</i>set<i> [setname]</i> | mem<i> [setname]</i> | fld<i> [fldname]}</i>
edit type
edit <i>{</i>first | last | count<i>}</i> <i>setname</i>
edit <i>{</i>own | prev | next<i>}</i> <i>setname</i>
edit <i>{</i>dba | opt | dchain | nextslot<i>}</i>
edit hex
exit
goto<i> {dba</i> | nextrec | prevrec <i>}</i>
goto<i> {</i>first | last |<i> </i>own | prev | next<i>} setname</i>
goto <i>{</i>file<i> {filenum</i> | <i>filename}}</i>
help | ?  
nofields
notitles
reread
show<i> {</i>field<i> [fieldname]</i> | file<i> [filename]</i> | key <i>[keyname]}</i>
show<i> {</i>record <i>[recordname]</i> | set <i>[setname]}</i>
fields
titles
verify <i>setname</i></font>
</pre>
<p><a href="UG_Ch13.htm">Next Page</a></p>
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