Add Sys.isfreebsd

We have `Sys.is*` for all officially supported platforms except for
FreeBSD... until now! Previously, the only way to detect FreeBSD was
to check `Sys.KERNEL === :FreeBSD`, as `Sys.isbsd() && !Sys.isapple()`
will be insufficiently specific should we ever support other BSDs.

base/sysinfo.jl

@@ -22,6 +22,7 @@ export BINDIR,
        total_memory,
        isapple,
        isbsd,
+       isfreebsd,
        islinux,
        isunix,
        iswindows,
@@ -301,6 +302,18 @@ See documentation in [Handling Operating System Variation](@ref).
 """
 isbsd(os::Symbol) = (os == :FreeBSD || os == :OpenBSD || os == :NetBSD || os == :DragonFly || os == :Darwin || os == :Apple)
 
+"""
+    Sys.isfreebsd([os])
+
+Predicate for testing if the OS is a derivative of FreeBSD.
+See documentation in [Handling Operating System Variation](@ref).
+
+!!! note
+    Not to be confused with `Sys.isbsd()`, which is `true` on FreeBSD but also on other
+    BSD-based systems. `Sys.isfreebsd()` refers only to FreeBSD.
+"""
+isfreebsd(os::Symbol) = (os == :FreeBSD)
+
 """
     Sys.iswindows([os])
 
@@ -317,7 +330,7 @@ See documentation in [Handling Operating System Variation](@ref).
 """
 isapple(os::Symbol) = (os == :Apple || os == :Darwin)
 
-for f in (:isunix, :islinux, :isbsd, :isapple, :iswindows)
+for f in (:isunix, :islinux, :isbsd, :isapple, :iswindows, :isfreebsd)
     @eval $f() = $(getfield(@__MODULE__, f)(KERNEL))
 end
 

doc/src/base/base.md

@@ -285,6 +285,7 @@ Base.Sys.isunix
 Base.Sys.isapple
 Base.Sys.islinux
 Base.Sys.isbsd
+Base.Sys.isfreebsd
 Base.Sys.iswindows
 Base.Sys.windows_version
 Base.@static

doc/src/manual/handling-operating-system-variation.md

@@ -3,17 +3,18 @@
 When writing cross-platform applications or libraries, it is often necessary to allow for
 differences between operating systems. The variable `Sys.KERNEL` can be used to handle such
 cases. There are several functions in the `Sys` module intended to make this easier:
-`isunix`, `islinux`, `isapple`, `isbsd`, and `iswindows`. These may be used as follows:
+`isunix`, `islinux`, `isapple`, `isbsd`, `isfreebsd`, and `iswindows`. These may be used
+as follows:
 
 ```julia
 if Sys.iswindows()
     windows_specific_thing(a)
 end
 ```
 
-Note that `islinux` and `isapple` are mutually exclusive subsets of `isunix`. Additionally,
-there is a macro `@static` which makes it possible to use these functions to conditionally hide
-invalid code, as demonstrated in the following examples.
+Note that `islinux`, `isapple`, and `isfreebsd` are mutually exclusive subsets of `isunix`.
+Additionally, there is a macro `@static` which makes it possible to use these functions to
+conditionally hide invalid code, as demonstrated in the following examples.
 
 Simple blocks:
 

test/osutils.jl

@@ -1,6 +1,6 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
-@testset "isunix/islinux/iswindows" begin
+@testset "Operating system predicates" begin
     @test !Sys.isunix(:Windows)
     @test !Sys.islinux(:Windows)
     @test Sys.islinux(:Linux)
@@ -12,6 +12,11 @@
     @test !Sys.isapple(:Windows)
     @test Sys.isunix(:Darwin)
     @test Sys.isunix(:FreeBSD)
+    @test Sys.isbsd(:FreeBSD)
+    @test Sys.isfreebsd(:FreeBSD)
+    @test Sys.isbsd(:OpenBSD)
+    @test !Sys.isfreeBSD(:OpenBSD)
+    @test Sys.isbsd(:Darwin)
     @test_throws ArgumentError Sys.isunix(:BeOS)
     if !Sys.iswindows()
         @test Sys.windows_version() == v"0.0.0"