3.2. System library

Scripting manual Scripting introduction Introduction to resources Creating your first script in C# Creating your first script in JavaScript Creating your first script in Lua About native functions. Simple interface to TCC, a fast runtime C compiler by Fabrice Bellard, it allows a Lua script to compile C code and register it at runtime as Lua-callable C funcions. javierguerragiraldez/lua-tcc.

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To start with lets create a very basic Lua script and save it as 'script.lua': - Start - Script: script.lua print('I am using Lua from within C') - End There, told you it was a very basic script! When we embed Lua into C, we will ask Lua to open and run that file. For more examples, see the end of the tutorial. Now for the C code.

This library contains various system functions.

It provides all its functions inside the table SysUtils.

System library

Function name Description

System library
Function name	Description
SysUtils.Sleep(Milliseconds) Suspends the execution of the script for the specified number of `Milliseconds`. After the specified period has expired, script execution resumes.
SysUtils.GetTickCount	SysUtils.GetTickCount() Returns an increasing clock tick count. It is useful for time measurements, but no assumtions should be made as to the interval between the ticks.
bFlagExists = SysUtils.FileExists(FileName) Check whether a particular file exists in the filesystem. Returns in `bFlagExists` the value `true` if file with name `FileName` exists on the disk, or `false` otherwise.
SysUtils.DirectoryExists	bFlagExists = SysUtils.DirectoryExists(Directory) Checks whether `Directory` exists in the filesystem and is actually a directory. If this is the case, the function returns in `bFlagExists` the value `true` otherwise `false` is returned.
Attr = SysUtils.FileGetAttr(FileName) Returns in `Attr` the attribute settings of file `FileName`. See the detail explanations of the returned value here.
SysUtils.FindFirst	Handle, FindData = SysUtils.FindFirst(Path) Looks for files that match the `Path`, generally with wildcards. If no file is found, `Handle` will be `nil`. When at least one item is found, the returned `Handle` may be used in subsequent `SysUtils.FindNext` to find other occurences of the same pattern. The `FindData` table contains information about the file or directory found. The field of the `FindData` table are: `Name` : The file name (without path). `Attr` : The file attributes of the file (see details here). `Size` : The size of the file in bytes. `Time` : The time stamp of the file (seconds since Jan 01 1970)
Result, FindData = SysUtils.FindNext(Handle) Finds the next occurrence of a search sequence initiated by `FindFirst` by re-using the `Handle` returned previously. Returned `Result` will be non-nil if a file or directory is found and will be `nil` otherwise. The same notes mentionned for `SysUtils.FindFirst` applied here. Remark: The last `SysUtils.FindNext` call must always be followed by a `SysUtils.FindClose` call with the same `Handle`. Failure to do so will result in memory loss.
SysUtils.FindClose	SysUtils.FindClose(Handle) Ends a series of `SysUtils.FindFirst`/`SysUtils.FindNext` calls. Frees any memory used by these calls. It is absolutely necessary to do this call, or memory losses may occur.
bResult = SysUtils.CreateHardLink(Path, LinkName) Create the hard link `LinkName` to file `Path`. Returns `true` if successful, `false` otherwise.
SysUtils.CreateSymbolicLink	bResult = SysUtils.CreateSymbolicLink(Path, LinkName) Create the symbolic link `LinkName` to file or directory `Path`. Returns `true` if successful, `false` otherwise.
sTarget = SysUtils.ReadSymbolicLink(LinkName, Recursive) Read destination of the symbolic link `LinkName`. If `Recursive` is `true` and the link points to a link then it's resolved recursively until a valid file name that is not a link is found. Returns the path where the symbolic link `LinkName` is pointing to or an empty string when the link is invalid or the file it points to does not exist and `Recursive` is `true`.
SysUtils.PathDelim	SysUtils.PathDelim Allows a script to get from DC the system path delimiter. In Unix/Linux system will be a ' / ' and in Windows will be ' '
sName = SysUtils.ExtractFileName(FileName) Extract the filename part from a full path filename. The filename consists of all characters after the last directory separator character ('/' or ') or drive letter.
SysUtils.ExtractFilePath	sPath = SysUtils.ExtractFilePath(FileName) Extract the path from a filename (including drive letter). The path consists of all characters before the last directory separator character ('/' or '), including the directory separator itself.
sDir = SysUtils.ExtractFileDir(FileName) Extract only the directory part of `FileName`, including a drive letter. The directory name has NO ending directory separator, in difference with `SysUtils.ExtractFilePath`.
SysUtils.ExtractFileDrive	sDrive = SysUtils.ExtractFileDrive(FileName) Extract the drive part from a filename. Note that some operating systems do not support drive letters.
sExt = SysUtils.ExtractFileExt(FileName) Return the extension from a filename (all characters after the last '.' (dot), including the '.' character).
SysUtils.CreateDirectory	bResult = SysUtils.CreateDirectory(Directory) Create a chain of directories, `Directory` is the full path to directory. Returns `true` if `Directory` already exist or was created successfully. If it failed to create any of the parts, `false` is returned.

SysUtils.Sleep(Milliseconds)

Suspends the execution of the script for the specified number of Milliseconds.
After the specified period has expired, script execution resumes.

SysUtils.GetTickCount

SysUtils.GetTickCount()

Returns an increasing clock tick count. It is useful for time measurements, but no assumtions should be made as to the interval between the ticks.

bFlagExists = SysUtils.FileExists(FileName)

Check whether a particular file exists in the filesystem.

Returns in bFlagExists the value true if file with name FileName exists on the disk, or false otherwise.

SysUtils.DirectoryExists

bFlagExists = SysUtils.DirectoryExists(Directory)

Checks whether Directory exists in the filesystem and is actually a directory.

If this is the case, the function returns in bFlagExists the value true otherwise false is returned.

Attr = SysUtils.FileGetAttr(FileName)

Returns in Attr the attribute settings of file FileName.

See the detail explanations of the returned value here.

SysUtils.FindFirst

Handle, FindData = SysUtils.FindFirst(Path)

Looks for files that match the Path, generally with wildcards.

If no file is found, Handle will be nil.

When at least one item is found, the returned Handle may be used in subsequent SysUtils.FindNext to find other occurences of the same pattern.

The FindData table contains information about the file or directory found.

The field of the FindData table are:

Name : The file name (without path).
Attr : The file attributes of the file (see details here).
Size : The size of the file in bytes.
Time : The time stamp of the file (seconds since Jan 01 1970)

Result, FindData = SysUtils.FindNext(Handle)

Finds the next occurrence of a search sequence initiated by FindFirst by re-using the Handle returned previously.

Returned Result will be non-nil if a file or directory is found and will be nil otherwise.

The same notes mentionned for SysUtils.FindFirst applied here.

Remark: The last SysUtils.FindNext call must always be followed by a SysUtils.FindClose call with the same Handle. Failure to do so will result in memory loss.

SysUtils.FindClose

SysUtils.FindClose(Handle)

Ends a series of SysUtils.FindFirst/SysUtils.FindNext calls.

Frees any memory used by these calls.

It is absolutely necessary to do this call, or memory losses may occur.

bResult = SysUtils.CreateHardLink(Path, LinkName)

Create the hard link LinkName to file Path.

Returns true if successful, false otherwise.

SysUtils.CreateSymbolicLink

bResult = SysUtils.CreateSymbolicLink(Path, LinkName)

Create the symbolic link LinkName to file or directory Path.

Returns true if successful, false otherwise.

sTarget = SysUtils.ReadSymbolicLink(LinkName, Recursive)

Read destination of the symbolic link LinkName.

If Recursive is true and the link points to a link then it's resolved recursively until a valid file name that is not a link is found.

Returns the path where the symbolic link LinkName is pointing to or an empty string when the link is invalid or the file it points to does not exist and Recursive is true.

SysUtils.PathDelim

Allows a script to get from DC the system path delimiter.

In Unix/Linux system will be a ' / ' and in Windows will be ' '

sName = SysUtils.ExtractFileName(FileName)

Extract the filename part from a full path filename.

The filename consists of all characters after the last directory separator character ('/' or ') or drive letter.

SysUtils.ExtractFilePath

sPath = SysUtils.ExtractFilePath(FileName)

Extract the path from a filename (including drive letter).

The path consists of all characters before the last directory separator character ('/' or '), including the directory separator itself.

sDir = SysUtils.ExtractFileDir(FileName)

Extract only the directory part of FileName, including a drive letter.

The directory name has NO ending directory separator, in difference with SysUtils.ExtractFilePath.

SysUtils.ExtractFileDrive

sDrive = SysUtils.ExtractFileDrive(FileName)

Extract the drive part from a filename.

Note that some operating systems do not support drive letters.

sExt = SysUtils.ExtractFileExt(FileName)

Return the extension from a filename (all characters after the last '.' (dot), including the '.' character).

SysUtils.CreateDirectory

bResult = SysUtils.CreateDirectory(Directory)

Create a chain of directories, Directory is the full path to directory.

Returns true if Directory already exist or was created successfully. If it failed to create any of the parts, false is returned.

Lua has a very simple C API. You can run Lua code and access lua objects from C. Similarly, you can access C functions and libraries from Lua. In this post, we’ll primarily look at how to expose C functions to lua.

Install Lua

Let’s start off with the installation of lua. You can install lua using system package managers as

Mac:

Ubuntu:

You can also build lua from source. However, you have to build lua as a shared library and this can be a bit tricky.

Lua Scripting Roblox

Lua Stack

Communication between lua and C is held through stacks with each element in stack representing lua value (nil, number, string, etc.).

For example, a C wrapped function c_swap is called in lua as:

In C, you will receive arguments in a stack as

You will then read the arguments from the stack as (indexing for this stack starts with 1 like in lua):

This is actually unsafe because these calls will fail if value in the stack at the specified index is not a number. Following code uses auxiliary library lauxlib.h and is safer; it will raise errors instead of segfaulting.

Then, you will process the arguments and push the results to stack.

Stack will now look like

Since you need to communicate the number of return value to lua, you will <

Lua Scripting C