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{{Nasal Navigation}}
{{Nasal Navigation}}
== Nasal Core functions ==
This page contains documentation for the '''<code>io</code> namespace''' in [[Nasal]]. This namespace provides APIs for input/output (IO) operations on files. The <code>io</code> namespace is sourced from {{fgdata file|Nasal/io.nas}} and {{simgear file|simgear/nasal/iolib.c}}.
=== io.open(filename, mode="r") ===
 
== Functions ==
=== open(filename, mode="r") ===
Opens the file with the specified mode (as per ANSI fopen()) and returns a ghost object representing the filehandle. Failures are thrown as runtime errors as per die().  
Opens the file with the specified mode (as per ANSI fopen()) and returns a ghost object representing the filehandle. Failures are thrown as runtime errors as per die().  
=== io.close(filehandle) ===
 
=== close(filehandle) ===
Closes the specified file as per ANSI fclose().  
Closes the specified file as per ANSI fclose().  
=== io.read(filehandle, buf, len) ===
 
=== read(filehandle, buf, len) ===
Attempts to read length bytes from the filehandle into the beginning of the mutable string buf. Failures (including overruns when length > size(buf)) are thrown as runtime errors as per die(). Returns the number of bytes successfully read.  
Attempts to read length bytes from the filehandle into the beginning of the mutable string buf. Failures (including overruns when length > size(buf)) are thrown as runtime errors as per die(). Returns the number of bytes successfully read.  
=== io.write(filehandle, str) ===
 
=== write(filehandle, str) ===
Attempts to write the entirety of the specified string to the filehandle. Failures are thrown as runtime errors as per die(). Returns the number of bytes successfully written.  
Attempts to write the entirety of the specified string to the filehandle. Failures are thrown as runtime errors as per die(). Returns the number of bytes successfully written.  
=== io.seek(filehandle, position, whence)
 
As ANSI fseek(). Attempts to seek to the specified position based on the whence value (which must be one of io.SEEK_SET, io.SEEK_END, or io.SEEK_CUR).  
=== seek(filehandle, position, whence)
=== io.tell(filehandle) ===
As ANSI fseek(). Attempts to seek to the specified position based on the whence value (which must be one of io.SEEK_SET, io.SEEK_END, or io.SEEK_CUR).
=== tell(filehandle) ===
Returns the current seek position of the filehandle.  
Returns the current seek position of the filehandle.  
=== io.readln(filehandle) ===
 
=== readln(filehandle) ===
Reads and returns a single text line from the filehandle. Interprets both "\n" and "\r\n" as end of line markers, and does not include the "\r" or "\n" bytes in the returned string. End of file or error is signaled by returning nil.  
Reads and returns a single text line from the filehandle. Interprets both "\n" and "\r\n" as end of line markers, and does not include the "\r" or "\n" bytes in the returned string. End of file or error is signaled by returning nil.  
=== io.stat(filename) ===
 
=== stat(filename) ===
Calls unix or win32 stat() on the specified file name and returns a seven element array whose contents are, in order: dev, ino, mode, nlink, uid, gid, rdef, size, atime, mtime, ctime. Errors are signaled as exceptions as per die().  
Calls unix or win32 stat() on the specified file name and returns a seven element array whose contents are, in order: dev, ino, mode, nlink, uid, gid, rdef, size, atime, mtime, ctime. Errors are signaled as exceptions as per die().  


== Reading files ==
=== basename() ===
The following description of functions refers to "$FG_ROOT\data\Nasal\io.nas".
=== io.basename() ===
Works like standard Unix command basename. Returns the file name from a given path.
Works like standard Unix command basename. Returns the file name from a given path.
<syntaxhighlight lang="nasal">
<syntaxhighlight lang="nasal">
io.basename(<path>);
io.basename(<path>);
</syntaxhighlight>
</syntaxhighlight>
=== io.dirname() ===
 
=== dirname() ===
Works like standard Unix command dirname. Returns the directory part from a given path.
Works like standard Unix command dirname. Returns the directory part from a given path.
<syntaxhighlight lang="nasal">
<syntaxhighlight lang="nasal">
io.basename(<path>);
io.basename(<path>);
</syntaxhighlight>
</syntaxhighlight>
=== io.readfile() ===
 
=== readfile() ===
Reads and returns a complete file as a string. Failures are thrown as runtime errors as per die().
Reads and returns a complete file as a string. Failures are thrown as runtime errors as per die().
<syntaxhighlight lang="nasal">
<syntaxhighlight lang="nasal">
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</syntaxhighlight>
</syntaxhighlight>


== Read FG PropertyList XML ==
=== read_properties() ===
The following description of functions refers to "$FG_ROOT\data\Nasal\io.nas".
=== io.read_properties() ===
Load XML file in FlightGear's native <PropertyList> format.           
Load XML file in FlightGear's native <PropertyList> format.           
If the second, optional target parameter is set, then the properties  
If the second, optional target parameter is set, then the properties  
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</syntaxhighlight>
</syntaxhighlight>


=== io.read_airport_properties() ===
=== read_airport_properties() ===
Load XML file in FlightGear's native <PropertyList> format.           
Load XML file in FlightGear's native <PropertyList> format.           
File will be located in the airport-scenery directories according to  
File will be located in the airport-scenery directories according to  
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</syntaxhighlight>
</syntaxhighlight>


== Write FG PropertyList XML ==
=== write_properties() ===
The following description of functions refers to "$FG_ROOT\data\Nasal\io.nas".
=== io.write_properties() ===
Write XML file in FlightGear's native <PropertyList> format.     
Write XML file in FlightGear's native <PropertyList> format.     
Returns the filename on success or nil on error. If the source is a props.Node that refers to a node in the main tree,  
Returns the filename on success or nil on error. If the source is a props.Node that refers to a node in the main tree,  
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</syntaxhighlight>
</syntaxhighlight>


== Read/Write Plain XML ==
{{Note|The following two functions are for reading generic XML files into     
This description of functions refers to "$FG_ROOT\data\Nasal\io.nas".
 
The following two functions are for reading generic XML files into     
the property tree and for writing them from there to the disk. The     
the property tree and for writing them from there to the disk. The     
built-in fgcommands (load, save, loadxml, savexml) are for FlightGear's
built-in fgcommands (load, save, loadxml, savexml) are for FlightGear's
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attributes. The two functions have their own limitations, but can       
attributes. The two functions have their own limitations, but can       
easily get extended to whichever needs. The underlying parsexml()       
easily get extended to whichever needs. The underlying parsexml()       
command will handle any XML file.
command will handle any XML file.}}


=== io.readxml() ===
=== readxml() ===
Reads an XML file from an absolute path and returns it as property   
Reads an XML file from an absolute path and returns it as property   
tree. All nodes will be of type STRING. Data are only written to     
tree. All nodes will be of type STRING. Data are only written to     
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</syntaxhighlight>
</syntaxhighlight>


=== io.writexml() ===
=== writexml() ===
Writes a property tree as returned by readxml() to a file. Children   
Writes a property tree as returned by readxml() to a file. Children   
with name starting with <prefix> are again turned into attributes of   
with name starting with <prefix> are again turned into attributes of   
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</syntaxhighlight>
</syntaxhighlight>


== Serializing Nasal types ==
[[Category:Nasal]]
Retrieved from "https://wiki.flightgear.org/Special:MobileDiff/104992"

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