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edits to exception handling section - next up is the Registry

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fyodor
2008-11-07 21:26:56 +00:00
parent f42b6c84c5
commit da08bf8a0d
1 changed files with 19 additions and 21 deletions
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docs/scripting.xml
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@@ -1364,37 +1364,35 @@ end
<title>Exception Handling</title>
<indexterm><primary>exceptions in NSE</primary></indexterm>
<para>
NSE provides an exception handling mechanism not present in
the plain Lua language. The exception handling is tailored
specifically for network I/O operations. The mechanism
NSE provides an exception handling mechanism which is not present in
the base Lua language. It is tailored
specifically for network I/O operations, and
follows a functional programming paradigm rather than an
object oriented programming paradigm. To create an exception
handler the <literal>nmap.new_try()</literal> API method is
used. This method returns a function, which takes a variable
number of arguments, assumed to be the return values of
object oriented one. The <function>nmap.new_try</function> API method is used to
create an exception handler. This method returns a function which takes a variable
number of arguments that are assumed to be the return values of
another function. If an exception is detected in the return
values (the first return value is false),
then the script execution is aborted and no
output is produced. Optionally you can pass a function to
the <literal>new_try()</literal> method which will be called
if an exception is caught. In this function you can perform
required clean up operations.</para>
output is produced. Optionally, you can pass a function to
<function>new_try</function> which will be called
if an exception is caught. The function would generally perform any required cleanup operations.
</para>
<para>
<xref linkend="nse-exception-handling" xrefstyle="select: label nopage"/> shows cleanup
exception handling at work. A new function named
<literal>catch</literal> is defined to simply close the
<function>catch</function> is defined to simply close the
newly created socket in case of an error. It is then used
to protect connection and communication attempts on that
socket. If no catch function is specified, execution of the
script aborts without further ado&mdash;open sockets
will remain open. If the verbosity level is at least one
or if the scan is performed in debugging mode a description
of the uncaught error condition is printed on standard output.
Note that it is currently not easily possible to group several
statements in one try block. It is also important to remember
that if the socket is not closed it will occupy memory
until the next run of Lua's garbage collector.
script aborts without further ado&mdash;open sockets will
remain open until the next run of Lua's garbage
collector. If the verbosity level is at least one or if the
scan is performed in debugging mode a description of the
uncaught error condition is printed on standard output.
Note that it is currently not easily possible to group
several statements in one try block.
</para>
@@ -1421,7 +1419,7 @@ try(socket:send(result))
try/catch mechanism is straightforward. The function should
return multiple values. The first value should be a Boolean
which is <literal>true</literal> upon successful completion of the function and
<literal>false</literal> otherwise. If the function completed successfully the try
<literal>false</literal> otherwise. If the function completed successfully, the try
construct consumes the indicator value and returns the
remaining values. If the function failed then the second
returned value must be a string describing the error