JuliaLang/julia#21197: accessing Cmd as an array of strings (#379)

README.md

@@ -148,6 +148,8 @@ Currently, the `@compat` macro supports the following syntaxes:
 
 * `@__MODULE__` is aliased to `current_module()` for Julia versions 0.6 and below. Versions of `Base.binding_module`, `expand`, `macroexpand`, and `include_string` were added that accept a module as the first argument. ([#22064])
 
+* `Cmd` elements can be accessed as if the `Cmd` were an array of strings for 0.6 and below ([#21197]).
+
 * `Val(x)` constructs `Val{x}()`. ([#22475])
 
 * `chol` and `chol!` for `UniformScalings` ([#22633]).

src/Compat.jl

@@ -601,6 +601,17 @@ else
     const collect = Base.collect
 end
 
+# https://github.com/JuliaLang/julia/pull/21197
+if VERSION < v"0.7.0-DEV.257"
+    # allow the elements of the Cmd to be accessed as an array or iterator
+    for f in (:length, :endof, :start, :eachindex, :eltype, :first, :last)
+        @eval Base.$f(cmd::Cmd) = $f(cmd.exec)
+    end
+    for f in (:next, :done, :getindex)
+        @eval Base.$f(cmd::Cmd, i) = $f(cmd.exec, i)
+    end
+end
+
 # https://github.com/JuliaLang/julia/pull/21378
 if VERSION < v"0.6.0-pre.beta.455"
     import Base: ==, isless

test/runtests.jl

@@ -1882,6 +1882,17 @@ let
     @test_throws MethodError Dates.Month(1) < Dates.Day(1)
 end
 
+# PR #21197
+let c = `ls -l "foo bar"`
+    @test collect(c) == ["ls", "-l", "foo bar"]
+    @test first(c) == "ls" == c[1]
+    @test last(c) == "foo bar" == c[3] == c[end]
+    @test c[1:2] == ["ls", "-l"]
+    @test eltype(c) == String
+    @test length(c) == 3
+    @test eachindex(c) == 1:3
+end
+
 # PR 22629
 @test logdet(0.5) == log(det(0.5))