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     <h1 class ="postheader"><div align="right" padding=20>April 20, 2011&nbsp;&nbsp;</div><div align="left">Regular Expression Commands</div></h1>
     <div class="postcontent">
     <p>Greetings LLDB users. I want to start writing regular blog posts
         for the new and cool features and things you can do in LLDB. Today I
         will start with one that was just added: <b>regular expression commands</b>.
         What is a regular expression command? It is a command that you can
         define by giving it a command name, where the command will have its raw arguments be
         matched against one or more regular expressions. The first regular
         expression to match your command's raw arguments wins and gets to
         use substitutions to place argument snippets into a new command that
         will get executed.</p>

         <p>Lets supposed we want to use the <code>"f"</code> as a command to
             select a frame by frame index. The command to select a frame by the
             frame index is the <code>"frame select &lt;num&gt;"</code> command
             which you might not always want to type out (even with out command
             completion).
             We can make this a bit easier this using a regular expression command:
         <p>
         <code>(lldb) command regex f 's/([0-9]+)/frame select %1/'</code>
         </p>

         <p><code>"command regex f"</code> tells the interpreter to create a new
             regex command named <code>"f"</code>, and when a command is entered
             on the command line that starts with <code>"f"</code>, it will match
             the remaining command text against the regular expression
             <code>"([0-9]+)"</code>, and it if matches, it will substitute any
             parenthesized subexpressions as needed. Here we enclosed the number
             regular expression <code>"[0-9]+"</code> in parentheses which will
             save the results in the first match and allow the matching string
             to be substitued into the result <code>"frame select %1"</code>.
             So now we can use our new command and it will show us what command
             resulted from our regular expression substitution:
         <p>
             <p>
             <code>(lldb) f 12<br>
                   frame select 12
             </code>
             </p>
         <p>Leading spaces will always be stripped, but there may be trailing spaces
             since we are processing the remaining raw command string that follows
             the initial <code>f</code> command name, plus any leading spaces. The regular expression
             is also just looking for any sequence of one or more digits. Our
             current regular expression will actually match <code>"f 11 22 33"</code>:
             <p>
             <code>(lldb) f 11 22 33<br>
                   frame select 11
             </code>
             </p>
             Since this isn't desired, we should make the regular expression more complete by checking for
             the start of the line (<code>^</code>) and the end of the line (<code>$</code>)
             and also allow for zero or more spaces (<code>[[:space:]]*</code>)
             to come after the number. Our newer and safer regular expression command line looks like:
             <p>
             <code>(lldb) command regex f 's/^([0-9]+)[[:space:]]*$/frame select %1/'</code>
             </p>
             <p>Now we can type in a command as <code>"f 12  "</code> (note the trailing
                 spaces), and still get correct substitutions, while our previous
                 example of <code>"f 11 22 33"</code> will no longer match:
                 <p>
                 <code>(lldb) f 11 22 33<br>
                     error: Command contents '11 22 33' failed to match any regular expression in the 'f' regex command.
                 </code>
             <p>Lets take this a bit further by also using the <code>f</code> command
                 to emulate GDB's <code>finish</code> command when it is typed without
                 any arguments. We will also modify this command to watch for a single
                 "+" or "-" followed by a digit to signify a relative frame change
                 using the frame select command with the --relative option:
             </p>
             <p>
             <code>(lldb) frame select --relative &lt;offset&gt;</code>
             <p>
                 Multiple regular expressions can be entered in on the command line
                 or using the multi-line mode when typing in a live LLDB debug session.
                 Below the text in bold is user entered:
             <p>
             <code>
                 (lldb) <b>commands regex f</b><br>
                 Enter regular expressions in the form 's/&lt;regex&gt;/&lt;subst&gt;/' and terminate with an empty line:<br>
                 <b>s/^([0-9]+)[[:space:]]*$/frame select %1/<br>
                 s/^([+-][0-9]+)[[:space:]]*$/frame select --relative=%1/<br>
                 s/^[[:space:]]*$/finish/</b><br>
 <br>
                 (lldb) <b>f</b><br>
                 finish<br>
                 ...<br>
                 (lldb) <b>f -1</b><br>
                 frame select --relative=-1<br>
                 ...<br>
                 (lldb) <b>f +1</b><br>
                 frame select --relative=+1<br>
                 ...<br>
                 (lldb) <b>f 12</b><br>
                 frame select 12<br>
             </code>
             </p>
             <p>I hope you can see the possilbities in how you can customize your
                 command line experience in LLDB using these commands. You can add
                 any regular expression commands to your <b>~/.lldbinit</b> file to
                 always have your regular expression commands defined in your debug
                 sessions.

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	<h1 class ="postheader"><div align="right" padding=20>April 20, 2011  </div><div align="left">Regular Expression Commands</div></h1>
	<div class="postcontent">
	<p>Greetings LLDB users. I want to start writing regular blog posts
	for the new and cool features and things you can do in LLDB. Today I
	will start with one that was just added: <b>regular expression commands</b>.
	What is a regular expression command? It is a command that you can
	define by giving it a command name, where the command will have its raw arguments be
	matched against one or more regular expressions. The first regular
	expression to match your command's raw arguments wins and gets to
	use substitutions to place argument snippets into a new command that
	will get executed.</p>

	<p>Lets supposed we want to use the <code>"f"</code> as a command to
	select a frame by frame index. The command to select a frame by the
	frame index is the <code>"frame select <num>"</code> command
	which you might not always want to type out (even with out command
	completion).
	We can make this a bit easier this using a regular expression command:
	<p>
	<code>(lldb) command regex f 's/([0-9]+)/frame select %1/'</code>
	</p>

	<p><code>"command regex f"</code> tells the interpreter to create a new
	regex command named <code>"f"</code>, and when a command is entered
	on the command line that starts with <code>"f"</code>, it will match
	the remaining command text against the regular expression
	<code>"([0-9]+)"</code>, and it if matches, it will substitute any
	parenthesized subexpressions as needed. Here we enclosed the number
	regular expression <code>"[0-9]+"</code> in parentheses which will
	save the results in the first match and allow the matching string
	to be substitued into the result <code>"frame select %1"</code>.
	So now we can use our new command and it will show us what command
	resulted from our regular expression substitution:
	<p>
	<p>
	<code>(lldb) f 12<br>
	frame select 12
	</code>
	</p>
	<p>Leading spaces will always be stripped, but there may be trailing spaces
	since we are processing the remaining raw command string that follows
	the initial <code>f</code> command name, plus any leading spaces. The regular expression
	is also just looking for any sequence of one or more digits. Our
	current regular expression will actually match <code>"f 11 22 33"</code>:
	<p>
	<code>(lldb) f 11 22 33<br>
	frame select 11
	</code>
	</p>
	Since this isn't desired, we should make the regular expression more complete by checking for
	the start of the line (<code>^</code>) and the end of the line (<code>$</code>)
	and also allow for zero or more spaces (<code>[[:space:]]*</code>)
	to come after the number. Our newer and safer regular expression command line looks like:
	<p>
	<code>(lldb) command regex f 's/^([0-9]+)[[:space:]]*$/frame select %1/'</code>
	</p>
	<p>Now we can type in a command as <code>"f 12 "</code> (note the trailing
	spaces), and still get correct substitutions, while our previous
	example of <code>"f 11 22 33"</code> will no longer match:
	<p>
	<code>(lldb) f 11 22 33<br>
	error: Command contents '11 22 33' failed to match any regular expression in the 'f' regex command.
	</code>
	<p>Lets take this a bit further by also using the <code>f</code> command
	to emulate GDB's <code>finish</code> command when it is typed without
	any arguments. We will also modify this command to watch for a single
	"+" or "-" followed by a digit to signify a relative frame change
	using the frame select command with the --relative option:
	</p>
	<p>
	<code>(lldb) frame select --relative <offset></code>
	<p>
	Multiple regular expressions can be entered in on the command line
	or using the multi-line mode when typing in a live LLDB debug session.
	Below the text in bold is user entered:
	<p>
	<code>
	(lldb) <b>commands regex f</b><br>
	Enter regular expressions in the form 's/<regex>/<subst>/' and terminate with an empty line:<br>
	<b>s/^([0-9]+)[[:space:]]*$/frame select %1/<br>
	s/^([+-][0-9]+)[[:space:]]*$/frame select --relative=%1/<br>
	s/^[[:space:]]*$/finish/</b><br>
	<br>
	(lldb) <b>f</b><br>
	finish<br>
	...<br>
	(lldb) <b>f -1</b><br>
	frame select --relative=-1<br>
	...<br>
	(lldb) <b>f +1</b><br>
	frame select --relative=+1<br>
	...<br>
	(lldb) <b>f 12</b><br>
	frame select 12<br>
	</code>
	</p>
	<p>I hope you can see the possilbities in how you can customize your
	command line experience in LLDB using these commands. You can add
	any regular expression commands to your <b>~/.lldbinit</b> file to
	always have your regular expression commands defined in your debug
	sessions.

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