Kotlin for loop not printing in Kotlin Script

Question

I'm new to Kotlin and I'm playing with the for loop, in Kotlin Script (*.kts file) I have this in the file:

for (i in 1..5) print("$i, ")

I did think it would print the number 1 through 5 separated by commas in one line like this:

1, 2, 3, 4, 5,

But instead I don't get any output on the command line. I'm running this on a Mac via

kotlin ranges.kts

If I put anything behind this single for loop, like a seperate println() or if I replace the print in the loop with println, it works and gives me output.

I don't get this behaviour. Can anyone explain this to me?

Edit1: Versions: kotlin: 1.3.71 MacOS 10.15.4 (Catalina)

Well for me it does prints: 1, 2, 3, 4, 5, ##scratch##generated##kotlin.Unit — Animesh Sahu
– Animesh Sahu, Commented Apr 15, 2020 at 8:31
Kotlin 1.3.72 @ Windows 10 1909. Maybe it happened because i was using REPL in running the script. — Animesh Sahu
– Animesh Sahu, Commented Apr 24, 2020 at 7:46

Raman · Accepted Answer · 2020-04-14 22:25:34Z

3

This has nothing to do with the for loop and everything to do with print. It works if you add System.out.flush() at the end of the script. By default, writes to System.out (which print uses under the hood) don't always flush, and its likely that the Kotlin script runner isn't flushing the standard output stream before exiting.

This is also why using println works, as you noted -- if you look at the implementation of println in PrintStream, you'll see that it does flush its internal text and character output streams.

I created issue https://youtrack.jetbrains.com/issue/KT-38263.

edited Apr 14, 2020 at 22:25

answered Apr 14, 2020 at 18:10

Raman

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1 Comment

gidds Over a year ago

In addition: prinln() calls are far more common than print(), for this reason and others. If you want to print several things you can format them first — e.g. println((1..5).joinToString()).

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