TEKlib / Lua5 module reference manual
By Timm S. Müller -
Copyright © 2005 TEK neoscientists. All rights reserved.
Introduction
The Lua5 module implements the Lua (v5) scripting language interpreter
as a standalone TEKlib module, and it extends the regular set of Lua's
inbuilt libraries with a 'tek' library. The 'tek' library operates in
TEKlib's virtual filesystem namespace, adding much-needed functionality
(such as file and directory examination and argument parsing), while
it retains the semantics of the 'io' and 'os' libraries to a large extent.
On many platforms the 'io' and 'os' libraries are also available (for
compatibility with existing scripts), but the use of the 'tek' library is
encouraged for the sake of a powerful, yet fully portable OS and
filesystem abstraction.
SYNOPSIS
L = TOpenModule("lua5", version, tags)
lua_State* TSTRPTR TUINT16 TTAGITEM*
TAGS
None currently defined
FUNCTION
Create a new Lua interpreter instance.
When the Lua interpreter instance is no longer needed, it must
be passed to
exec:TCloseModule for freeing all associated memory.
Quite untypically, the interpreter instance returned by
exec:TOpenModule
is different from the module base, and the macro
LUABASE
must be
applied to the instance pointer before passing it to
exec:TCloseModule,
as shown below:
lua_State *L;
/* open Lua interpreter */
L = TOpenModule("lua5", 0, TNULL);
if (L)
{
/* use interpreter here */
/* close Lua intepreter */
TCloseModule(LUABASE(L))
}
tek.close ([file])
Equivalent to file:close
. Without a file, closes the default output file.
tek.flush ()
Equivalent to file:flush
over the default output file.
tek.input ([file])
When called with a file name, it opens the named file, and sets its
handle as the default input file. When called with a file handle,
it simply sets that file handle as the default input file. When called
without parameters, it returns the current default input file.
In case of errors this function raises the error, instead of returning
an error code.
tek.lines ([filename])
Opens the given file name in read mode and returns an iterator function that,
each time it is called, returns a new line from the file. Therefore, the
construction
for line in tek.lines(filename) do ... end
will iterate over all lines of the file. When the iterator function detects
the end of file, it returns nil (to finish the loop) and automatically closes
the file.
The call tek.lines()
(without a file name) is equivalent to
tek.input():lines()
, that is, it iterates over the lines of the default
input file.
tek.open (filename [, mode])
This function opens a file, in the mode specified in the string mode.
It returns a new file handle, or, in case of errors, nil plus an error
message.
The mode string can be any of the following:
-
"r" read mode (the default);
-
"w" write mode;
-
"a" append mode;
-
"r+" update mode, all previous data is preserved;
-
"w+" update mode, all previous data is erased;
-
"a+" append update mode, previous data is preserved, writing is only allowed at the end of file.
The mode string may also have a b at the end, which is provided for
compatibility with standard C libraries.
tek.output ([file])
Similar to tek.input
, but operates over the default output file.
tek.read (format1, ...)
Equivalent to tek.input():read
.
tek.type (obj)
Checks whether obj is a valid file handle. Returns the string "file" if obj is
an open file handle, "closed file" if obj is a closed file handle, and nil if
obj is not a file handle.
tek.write (value1, ...)
Equivalent to tek.output():write
.
file:close ()
Closes file.
file:examine ()
Examines a file's attributes and returns its type, size and modification
date to the caller. This is similar to lock:examine
, only that type
is always 1 (a regular file). The size returned is in bytes, the date is
a continuous number representing a day in the Julian system; it can be
used in arithmetics and converted using tek.date()
.
file:flush ()
Saves any written data to file.
file:lines ()
Returns an iterator function that, each time it is called, returns a new line
from the file. Therefore, the construction
for line in file:lines() do ... end
will iterate over all lines of the file. (Unlike tek.lines
, this function does
not close the file when the loop ends.)
file:read (format1, ...)
Reads the file file, according to the given formats, which specify what to read. For each format, the function returns a string (or a number) with the characters read, or nil if it cannot read data with the specified format. When called without formats, it uses a default format that reads the entire next line (see below).
The available formats are
-
"*n" reads a number; this is the only format that returns a number instead of a string.
-
"*a" reads the whole file, starting at the current position. On end of file, it returns the empty string.
-
"*l" reads the next line (skipping the end of line), returning nil on end of file. This is the default format.
-
number reads a string with up to that number of characters, returning nil on end of file. If number is zero, it reads nothing and returns an empty string, or nil on end of file.
file:seek ([whence] [, offset])
Sets and gets the file position, measured from the beginning of the file, to the position given by offset plus a base specified by the string whence, as follows:
-
"set" base is position 0 (beginning of the file);
-
"cur" base is current position;
-
"end" base is end of file;
In case of success, function seek returns the final file position,
measured in bytes from the beginning of the file. If this function fails,
it returns nil, plus a string describing the error.
The default value for whence is "cur", and for offset is 0. Therefore,
the call
file:seek returns the current file position, without changing it;
the call file:seek("set") sets the position to the beginning of the file
(and returns 0); and the call file:seek("end") sets the position to the end
of the file, and returns its size.
file:write (value1, ...)
Writes the value of each of its arguments to the filehandle file. The
arguments must be strings or numbers. To write other values, use tostring
or string.format before write.
tek.addpart (part1, part2)
Adds part2, which can be a path part or a file, to the path part1.
The result (which will be in accordance to TEKlib's filesystem
naming conventions) is returned to the caller, or nil if the either
of the parts (or the combination thereof) is invalid.
tek.delete (filename)
Deletes the file of the given name. If the addressed object is a directory,
it must be empty for this function to succeed.
Returns a boolean to the caller, indicating whether the operation was
successful.
tek.makename (path)
Tries to convert a path or path component in host-style naming conventions
to a fully-qualified path/name in TEKlib's path naming conventions. The
resulting name is returned to the caller, or nil in case of an error.
The name resolution request will be sent to the handler that is responsible
for the current task's current directory. If the current directory is on a
device that does not implement this kind of action, nil is returned.
tek.mount (devname, handlername [, initstring])
This function tries to mount the named device using the specified handler.
Optionally, an initstring is passed to the handler for initialization.
Returns a boolean to the caller, which indicates success.
tek.rename (oldname, newname)
Renames the file or directory specified by oldname to newname. If an object
of the new name already exists then an error is returned.
Both oldname and newname can contain path parts, in which case
the object will be moved across directories on the same filesystem.
Attempts to rename an object across different filesystems will fail.
Returns a boolean to the caller, indicating whether the operation was
successful.
tek.cdlock (lock)
Change the current task's current directory to the lock specified.
If successful, the lock on the previous current directory will be
returned to the caller. If the current task has no current directory,
or if an error occured, nil is returned.
tek.lock (filename [, exclusive])
Obtains a lock on a filesystem object (file or directory). The lock,
if successful, is returned to the caller, otherwise nil.
By default, the locking mode is shared, which means that mutiple
accessors can access the object at the same time. If the second
argument is true, then an exclusive (or read/write) lock is
attempted, which locks out other accessors from simultaneous use
of the object.
Warning: Not all operating systems actually implement all locking
modes at this time. Locks aren't currently enforced under POSIX.
tek.makedir (name)
Create a new directory of the given name. If successful, a shared lock
to the newly created directory will be returned to the caller. Otherwise,
the return value is nil.
tek.unlock (lock)
Releases a lock which was previously obtained with tek.lock
.
lock:unlock ()
Releases the lock.
lock:assign (devicename)
Assigns a logical device name to the specified lock. devicename
must be without a trailing colon. A boolean is returned to the caller,
indicating whether the assign succeeded. If successful, the lock has
been relinquished and is no longer valid.
lock:examine ()
Examines a lock's attributes and returns its type, size and modification
date to the caller. This is similar to file:examine
, only that type
can be 1 (a regular file), 2 (a directory), or 0 (unknown).
The size returned is in bytes, the date is a continuous number
representing a day in the Julian system; it can be used in arithmetics
and converted using tek.date()
.
lock:exnext ()
If the lock refers to a directory, then this method examines the
directory content's next entry and returns its name, type, size and
modification date to the caller. Returns nil if the end of the
directory is reached.
lock:nameof ()
Returns the name of the object which the lock refers to.
tek.clock ()
Returns the number of seconds that has passed since some starting point in
time, which is specific to the underlying operating system; it can be the
beginning of the operating system's "epoch", since the application was
started, or some other entity which is defined outside the scope of this
library.
tek.time ([table])
Returns the current date/time when called without arguments, or a date/time
representing the date and time specified by the given table. This table must
have fields year, month, and day, and may have fields hour, min, sec
(for a description of these fields, see the tek.date
function).
The returned value represents a day in the Julian date system; it can be used
in arithmetics and converted using tek.date()
.
tek.date ([format [, time]])
Returns a string or a table containing date and time, formatted according to
the given string format.
If the time argument is present, this is the date/time to be formatted (see
the tek.time
function for a description of this value). Otherwise, date
formats the current date/time.
If format starts with !, then the date/time is formatted in Coordinated Universal
Time. After that optional character, if format is *t, then date returns a
table with the following fields: year (four digits), month (1--12), day (1--31),
hour (0--23), min (0--59), sec (0--61), wday (weekday, Sunday is 1), yday (day
of the year).
If format is not *t, then date returns the date/time as a string, formatted
according to the same rules as the C function strftime. (Note, however, that
only the "%c" format specifier is currently supported.)
When called without arguments, date returns a reasonable date and time
representation that depends on the host system and on the current locale
(that is, tek.date()
is equivalent to tek.date("%c")
).
tek.readargs (template, ...)
Parse an argument list according to a template, and if the arguments match the
given template, return them to the caller in the order specified by the
template. If the argument list do not match the template, the return value is
nil.
Arguments in the template are separated with commas. Each argument consists
of a name, an optional alias, and an optional set of qualifiers. Example:
-s=SOURCE/A/M,-d=DEST/A/K
Unless qualified with /A, an argument is optional and does not necessarily
have to appear in the argument list. If an argument is present, it will be
in the list of return values at the same position as specified in the template,
otherwise the return value at its position is nil. An argument without
qualifiers represents a optional string argument. Qualifiers:
-
/S - Switch. This is considered a boolean variable.
When this option is present, true will be returned.
-
/N - This argument is considered an integer in decimal notation.
-
/K - Keyword. The option will not be accepted unless the keyword
appears in the arguments.
-
/A - Required. This argument cannot be omitted. If not present,
readargs returns nil.
-
/M - Multiple strings. Any number of strings will be accepted for
this argument and returned as a table. Not more than one /M modifier should
appear in a template.
Example:
source, dest = tek.readargs("-s=SOURCE/A/M,-d=DEST/A/K", unpack(arg))
And this is how it would work:
SOURCE one two three DEST foo
|
valid; returns { "one", "two", "three" }, "foo"
|
DEST foo -s one
|
valid; returns { "one" }, "foo"
|
DEST foo
|
rejected; source missing
|
one two three foo
|
rejected; keyword missing
|
one two dest foo
|
valid; returns { "one", "two" }, "foo"
|
-s one two -d three four
|
valid; returns { "one", "two", "four" }, "three"
|
Generated Sat Oct 8 02:07:13 2005 from lua5.doc