From 2211e0314ebec11a1d8272f3ed201cf9c6d3d771 Mon Sep 17 00:00:00 2001
From: "Steven G. Johnson" <stevenj@mit.edu>
Date: Tue, 28 Mar 2017 12:29:14 -0400
Subject: [PATCH 1/2] access Cmd elements as an array of strings

---
 base/process.jl                             |  8 ++++++++
 doc/src/manual/running-external-programs.md | 12 ++++++++++++
 test/spawn.jl                               | 11 +++++++++++
 3 files changed, 31 insertions(+)

diff --git a/base/process.jl b/base/process.jl
index cd15390ca42d6..1b2961ac625c3 100644
--- a/base/process.jl
+++ b/base/process.jl
@@ -805,3 +805,11 @@ wait(x::Process)      = if !process_exited(x); stream_wait(x, x.exitnotify); end
 wait(x::ProcessChain) = for p in x.processes; wait(p); end
 
 show(io::IO, p::Process) = print(io, "Process(", p.cmd, ", ", process_status(p), ")")
+
+# 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 $f(cmd::Cmd) = $f(cmd.exec)
+end
+for f in (:next, :done, :getindex)
+    @eval $f(cmd::Cmd, i) = $f(cmd.exec, i)
+end
diff --git a/doc/src/manual/running-external-programs.md b/doc/src/manual/running-external-programs.md
index a179d9f5d006b..dbeef5f23969f 100644
--- a/doc/src/manual/running-external-programs.md
+++ b/doc/src/manual/running-external-programs.md
@@ -60,6 +60,18 @@ julia> open(`less`, "w", STDOUT) do io
 3
 ```
 
+The program name and the individual arguments in a command can be accessed
+and iterated over as if the command were an array of strings:
+```jldoctest
+julia> collect(`echo "foo bar"`)
+2-element Array{String,1}:
+ "echo"   
+ "foo bar"
+
+julia> `echo "foo bar"`[2]
+"foo bar"
+```
+
 ## [Interpolation](@id command-interpolation)
 
 Suppose you want to do something a bit more complicated and use the name of a file in the variable
diff --git a/test/spawn.jl b/test/spawn.jl
index 8b7582b191ad0..87d9bf169d85e 100644
--- a/test/spawn.jl
+++ b/test/spawn.jl
@@ -466,3 +466,14 @@ end
             Base.showerror(io::IO, e::Error19864) = print(io, "correct19864")
             throw(Error19864())'`),
     stderr=catcmd)) == "ERROR: correct19864"
+
+# accessing the command elements as an array or iterator:
+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

From 5560ea3c46188c588ff73f0b4f38a0c99ac73698 Mon Sep 17 00:00:00 2001
From: "Steven G. Johnson" <stevenj@mit.edu>
Date: Tue, 28 Mar 2017 12:33:31 -0400
Subject: [PATCH 2/2] whitespace

---
 doc/src/manual/running-external-programs.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/doc/src/manual/running-external-programs.md b/doc/src/manual/running-external-programs.md
index dbeef5f23969f..36e624f9f08f1 100644
--- a/doc/src/manual/running-external-programs.md
+++ b/doc/src/manual/running-external-programs.md
@@ -65,7 +65,7 @@ and iterated over as if the command were an array of strings:
 ```jldoctest
 julia> collect(`echo "foo bar"`)
 2-element Array{String,1}:
- "echo"   
+ "echo"
  "foo bar"
 
 julia> `echo "foo bar"`[2]