How to do and in if condition

[klugier]

Hello,

I have following code:

umk_exe := if os_family() == "unix" {
    if os() == "macos" {
        "umk"
    } else {
        "umk.out"
    }
} else {
    "umk"
}

However, I would like to simplify it to:

umk_exe := if os_family() == "unix" && os() != "macos" { "umk.out" } else { "umk" }

But, can not do it, due to following error:

$ just build
error: Expected '&&', '||', '{', '+', or '/', but found '!='
 ——▶ Justfile:6:45
  │
6 │ umk_exe := if os_family() == "unix" && os() != "macos" { "umk.out" } else { "umk" }
  │                                             ^^

just version:

just 1.43.0 (Windows)

[laniakea64]

There isn't currently a way to do and operation in an if condition.

For your specific case you could do:

umk_exe := if os_family() + os() =~ '^unix[^m]' {
  "umk.out"
} else {
  "umk"
}

since os_family() can only be unix or windows, and the only os() return value that starts with m is macos

https://just.systems/man/en/functions.html#system-information

[ShreeChaturvedi]

Your && line works from just 1.53.0 if you turn on unstable lists:

set unstable
set lists

umk_exe := if os_family() == "unix" && os() != "macos" { "umk.out" } else { "umk" }

On 1.43.0 that parse fails because && is not boolean and in if. Stay on nested ifs, which are stable and still the right approach if you do not want set lists:

umk_exe := if os_family() == "unix" {
  if os() != "macos" { "umk.out" } else { "umk" }
} else {
  "umk"
}

set lists is unstable, so this && form can still change.