How to prevent Ctrl-C from terminating a program during readline()

General Usage
1

Hi, the following simple code is my attempt to see if I can trap Ctrl-C during readline()

Say I’m writing a REPL for a simple language interpreter… obviously I don’t want user accidentally pressing Ctrl-C to cause program termination.

function enter()
    println("Enter a line:")
    try
        s = readline()
        println(s)
    catch ex
        if ex isa InterruptException
            println("Ctrl-C")
        else
            println("Other Exceptions")
        end
    end
end

enter()

But I find it is not able to get into the catch section.
When user presses Ctrl-C Julia exits… this output was from MacOS Catalina. (Julia on Unbuntu also cannot trap Ctrl-C but with a much lengthier stack trace):

$ julia test_readline.jl

Enter a line:
abcd^C

signal (2): Interrupt: 2
in expression starting at /Users/bryanso/GDrive/fun/julia/test_readline.jl:18
kevent at /usr/lib/system/libsystem_kernel.dylib (unknown line)
unknown function (ip: 0x0)
Allocations: 2508 (Pool: 2497; Big: 11); GC: 0

Would you mind giving me a hint on how to trap Ctrl-C so I can recover from it?

Thanks a lot.

2

Found this topic in FAQ!

But let me know if there are other ways.

How do I catch CTRL-C in a script?

Running a Julia script using “julia file.jl” does not throw InterruptException when you try to terminate it with CTRL-C (SIGINT). To run a certain code before terminating a Julia script, which may or may not be caused by CTRL-C, use atexit. Alternatively, you can use “julia -e ‘include(popfirst!(ARGS))’ file.jl” to execute a script while being able to catch InterruptException in the try block.

1 Like
3

Starting with Julia 1.5 you will be able to add the following line to your enter function to get the desired behavior

Base.exit_on_sigint(false)
2 Likes
4

Thanks! Looking forward to using it.