I know there is the Swift REPL and the Xcode playgrounds, but I wonder whether there is an alternative to ruby -e "<code>" or sh -c "<code>" in Swift where the given one line code would be executed as the result of the command?
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2 Answers
There isn't a direct equivalent (you can ask the swift command for its options with swift --help and see there's nothing like Ruby's -e).
But there's a workaround.
You can pass a Swift expression to the compiler direclty using echo and | (the "pipe") like this:
echo "print(42)" | swift
Result:
Welcome to Apple Swift version 2.1.1 ("700.1.101.9 700.1.78"). Type :help for assistance.
42
I guess it's similar to the behavior you were looking for.
We notice that it always prints the introduction sentence, but there's a way to fix this, by adding - at the end of the command, like this:
echo "print(42)" | swift -
Result:
42
When using literal strings, escape the double quotes:
echo "print(\"hello\")" | swift -
Result:
hello
You can execute any expression, even loops:
echo "for num in 1...5 { print(num) }" | swift -
Result:
1
2
3
4
5
etc.
It's still the REPL so it will give feedback about variables (omitting the - trick at the end), for example:
echo "let x = 42;print(x)" | swift
Result:
Welcome to Apple Swift version 2.1.1 ("700.1.101.9 700.1.78"). Type :help for assistance.
42
x: Int = 42
Comments
As of Swift version 5.8, you can now runs code directly from the command line with swift -e
bash-3.2$ swift --help | grep -e "-e "
-e <value> Executes a line of code provided on the command line
bash-3.2$ swift -e 'print("fofo")'
fofo
bash-3.2$ swift -e 'import Foundation ; var users = ["zoe", "joe", "albert", "james"] ; for user in users { print(user) }'
zoe
joe
albert
james
bash-3.2$
1 Comment
Lukáš Kubánek
This seems to be the correct answer starting with Swift 5.8.