11-error-handling.md

Error Handling

Rugo uses try / or for error handling. Three levels of control.

Silent Recovery

try alone returns nil on failure:

result = try `nonexistent_command`
# result is nil — script continues

Fire and forget:

try nonexistent_command
puts "still running"

Default Value

try ... or default returns a fallback on failure:

hostname = try `hostname` or "localhost"
puts hostname

use "conv"

port = try conv.to_i("not_a_number") or 8080
puts port   # 8080

Error Handler Block

try ... or err ... end runs a block on failure. The error message is available as the named variable. The last expression in the block becomes the result.

data = try `cat /missing/file` or err
  puts "Error: #{err}"
  "fallback"
end
puts data   # fallback

Shell commands work with try too:

result = try nonexistent_command or "default"
puts result   # default

Raising Errors

Use raise to signal errors from your own code. It works like Go's panic() under the hood and can be caught with try/or:

raise("something went wrong")

Paren-free syntax works too:

raise "something went wrong"

Use raise in functions to validate inputs:

def greet(name)
  if name == nil
    raise "name is required"
  end
  return "Hello, " + name
end

msg = try greet(nil) or err
  puts "Error: " + err
  "Hello, stranger"
end
puts msg   # Hello, stranger

Called without arguments, raise uses a default message:

result = try raise() or err
  err
end
puts result   # runtime error

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That's it! You now know enough Rugo to build real scripts. See the examples/ directory for more.