83 lines
3.1 KiB
Markdown
Vendored
83 lines
3.1 KiB
Markdown
Vendored
# mruby-errno
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Errno module for mruby
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This mrbgem provides the `Errno` module, which allows mruby programs to access system error numbers and their corresponding error messages. This is particularly useful for handling errors returned by underlying system calls.
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## Functionality
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The `mruby-errno` gem defines the `Errno` module and the `SystemCallError` class.
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### Accessing Error Constants
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The `Errno` module provides constants for various system errors. Each error constant corresponds to a specific system error number.
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Example:
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```ruby
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p Errno::EPERM::Errno # Output: 1 (or the system-specific value for EPERM)
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p Errno::EPERM.new.message # Output: "Operation not permitted"
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```
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### Raising and Rescuing System Call Errors
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The `SystemCallError` class is the base class for system call errors. You can raise instances of `SystemCallError` or its subclasses (like `Errno::EPERM`) and rescue them in your code.
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Example:
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```ruby
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begin
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raise Errno::EACCES, "my_method"
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rescue SystemCallError => e
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p e.class # Output: Errno::EACCES
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p e.errno # Output: 13 (or the system-specific value for EACCES)
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p e.message # Output: "Permission denied - my_method"
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p e.to_s # Output: "Permission denied - my_method"
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end
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# You can also rescue specific Errno constants
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begin
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# Simulate a system call that might fail
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# For example, trying to open a file without permissions
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raise Errno::ENOENT, "missing_file.txt"
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rescue Errno::ENOENT => e
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puts "Caught an ENOENT error: #{e.message}"
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# Output: Caught an ENOENT error: No such file or directory - missing_file.txt
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end
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```
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### Errno::NOERROR
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The `Errno::NOERROR` constant represents the absence of an error, typically with a value of 0.
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Example:
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```ruby
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p Errno::NOERROR::Errno # Output: 0
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```
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## Defining Error Types
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New error types and their corresponding numbers are defined in the `known_errors.def` file. The `gen.rb` script processes this file to generate the necessary C and Ruby code for the `Errno` module. This allows `mruby-errno` to be easily extended with new system error definitions.
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## License
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Copyright (c) 2013 Internet Initiative Japan Inc.
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Permission is hereby granted, free of charge, to any person obtaining a
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copy of this software and associated documentation files (the "Software"),
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to deal in the Software without restriction, including without limitation
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the rights to use, copy, modify, merge, publish, distribute, sublicense,
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and/or sell copies of the Software, and to permit persons to whom the
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Software is furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in
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all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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DEALINGS IN THE SOFTWARE.
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