Raku Programming/Files

Filehandle
Any interaction with files in Raku happens through a filehandle. A filehandle is an internal name for an external file. The  function makes the association between the internal name and the external name, while the   function breaks that association. Some IO handles are available for your use without the need to create them:  and   are connected to STDOUT and STDIN, the standard output and standard input streams, respectively. You will need to open every other filehandle on your own.

Paths
Always remember, that any path to a file within the program is with respect to the current working directory.

Open a file for reading
To open a file, we need to create a filehandle to it. This simply means that we create a (scalar) variable which will refer to the file from now on. The two argument syntax is the most common way to call the  function:   —where   is the external name of the file you want opened and   is the type of access. If successful, this returns an IO handle object which we can put into a scalar container:

The  opens the file in read-only mode. For brevity, you can omit the —since it is the default mode; and, of course, the   string can be passed directly, instead of passing it via a   variable.

Once we have a filehandle, we can read and perform other actions on the file.

New Way
Use slurp and spurt instead, as:

Read an opened file
The most general approach to file reading avails itself with the establishment of a connection to the resource via the  function, followed by the data consumption step, and terminating with an invocation of   on the file handle received during the opening procedure.

To transfer the file data immediately and completely into the program, the  function can be used. Commonly, this involves the obtained string's storage into a variable for further manipulations.

If a complete data consumption is, either because of a line-oriented programming task or memory considerations, undesirable, a line by line reading can be accomplished through the  function.

A file handle's employment enables the resource's reuse, but on the other hand obliges the programmer to attend its management. If the offered advantages do not merit these expenses, the functions mentioned above can work directly upon a file name represented by its string.

The complete file contents can be read by specifying the file name as a string and invoking the  upon it.

If this object-oriented approach does not befit one's style, the equivalent procedural variant is:

In the same mode, a file handle free processing on a line-by-line basis comprises:

Remember the option to insert the file name without storage in a variable, which curtails the above code passages even more. Transferring the complete file contents, in corollary, might be reduced to:

or

In order to access a file on a finer level of granularity, Raku of course provides facilities for a specified amount of characters' retrieval through the  function, which accepts the tally of characters to consume and returns a string representing the obtained data.

External resources

 * Rosetta Code's tasks related to file handling