CLI Basics part 3

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Wildcards

Several commands (including *Copy) allow you to specify more than one file by using a wildcard in the filename. The available wildcards are:

For example:
Fred* would match “Fred”, “Freddy”, “Freda” and “Frederick”;
Fred# would match “Freda” but not “Fred”, “Freddy” or “Frederick”;
Fred## would match “Freddy” but not “Fred”, “Freda” or “Frederick”.

System devices

RISC OS contains a number of system devices, which can be used in place of filenames if you want to send (or receive) data to/from somewhere other than a file:

For example, you can use the *Copy command to send a file to the printer:
*Copy MyFile printer:

Alternatively, you may want to run a command but are not interested in any screen output. This can be done by redirecting output to the null device:
*MyCommand { > null: }

For a full list of system devices, see SystemDevices Technical Details.

Filetype declarations

Command aliases were mentioned in part 2. Another special type of alias is used to declare the default action to be taken on encountering a filetype. These take the following forms:

Most of these declarations are only of use in the desktop, but a handful are also relevant while in the CLI. For example, the default settings for filetype FFE are:
Alias$RunType_FFE Exec %0
which means that, if a file of type FFE is entered as a command at the star prompt, the action taken will be to *Exec the file.

System path variables

The way RISC OS searches for files or commands is controlled by the system variables File$Path and RunPath, as follows:

Each entry in the path contains a directory name followed by a full stop. Entries are separated by commas; two commas in a row are treated as a null entry (i.e. the currently selected directory, also known as CSD). Hence a run path of Boot:Library.,,%. would cause “Boot:Library” to be searched first, followed by CSD and finally “%” (i.e. the current library directory).

There are occasions when you may want to change these settings. For example, if you wanted RISC OS to search $.MyLibrary in addition to the other directories in Run$Path, you might use:
*Set Run$Path <Run$Path>,$.MyLibrary.

For more information on File$Path and Run$Path, see FileSwitch Paths To Search For Files.

Further reading

• System Variables in the Programmer’s Reference Manual.

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