process IO: add test for #22832

Fixes #14747

Author: vtjnash

base/shell.jl

@@ -285,11 +285,11 @@ This function may be useful in concert with the `windows_verbatim` flag to
 
 ```julia
 wincmd(c::String) =
-   run(Cmd(Cmd(["cmd.exe", "/s /c \" \$c \""]);
+   run(Cmd(Cmd(["cmd.exe", "/s /c \\" \$c \\""]);
            windows_verbatim=true))
 wincmd_echo(s::String) =
    wincmd("echo " * Base.shell_escape_wincmd(s))
-wincmd_echo("hello \$(ENV["USERNAME"]) & the \"whole\" world! (=^I^=)")
+wincmd_echo("hello \$(ENV["USERNAME"]) & the \\"whole\\" world! (=^I^=)")
 ```
 
 But take note that if the input string `s` contains a `%`, the argument list
@@ -316,7 +316,7 @@ run(setenv(`cmd /C echo %cmdargs%`, "cmdargs" => cmdargs))
     ```julia
     to_print = "All for 1 & 1 for all!"
     to_print_esc = Base.shell_escape_wincmd(Base.shell_escape_wincmd(to_print))
-    run(Cmd(Cmd(["cmd", "/S /C \" break | echo \$(to_print_esc) \""]), windows_verbatim=true))
+    run(Cmd(Cmd(["cmd", "/S /C \\" break | echo \$(to_print_esc) \\""]), windows_verbatim=true))
     ```
 
 With an I/O stream parameter `io`, the result will be written there,

test/read.jl

@@ -98,30 +98,27 @@ s = io(text)
 close(s)
 push!(l, ("PipeEndpoint", io))
 
-#FIXME See https://github.com/JuliaLang/julia/issues/14747
-#      Reading from open(::Command) seems to deadlock on Linux
-#=
-if !Sys.iswindows()
 
-# Windows type command not working?
-# See "could not spawn `type 'C:\Users\appveyor\AppData\Local\Temp\1\jul3516.tmp\file.txt'`"
-#https://ci.appveyor.com/project/StefanKarpinski/julia/build/1.0.12733/job/hpwjs4hmf03vs5ag#L1244
-
-# Pipe
+# Pipe (#14747)
 io = (text) -> begin
     write(filename, text)
-    open(`$(Sys.iswindows() ? "type" : "cat") $filename`)[1]
-#    Was open(`echo -n $text`)[1]
-#    See https://github.com/JuliaLang/julia/issues/14747
+    # we can skip using shell_escape_wincmd, since ", ^, and % aren't legal in
+    # a filename, so unconditionally wrapping in " is sufficient (okay, that's
+    # a lie, since ^ and % actually are legal, but DOS is broken)
+    if Sys.iswindows()
+        cmd = Cmd(["cmd.exe", "/c type \"$(replace(filename, '/' => '\\'))\""])
+        cmd = Cmd(cmd; windows_verbatim=true)
+        cmd = pipeline(cmd, stderr=devnull)
+    else
+        cmd = `cat $filename`
+    end
+    open(cmd)
 end
 s = io(text)
 @test isa(s, IO)
-@test isa(s, Pipe)
+@test isa(s, Base.Process)
 close(s)
-push!(l, ("Pipe", io))
-
-end
-=#
+push!(l, ("Process", io))
 
 
 open_streams = []
@@ -140,7 +137,6 @@ end
 verbose = false
 
 for (name, f) in l
-    local f
     local function io(text=text)
         local s = f(text)
         push!(open_streams, s)
@@ -319,9 +315,9 @@ for (name, f) in l
     text = old_text
     write(filename, text)
 
-    if !(typeof(io()) in [Base.PipeEndpoint, Pipe, TCPSocket])
+    if !isa(io(), Union{Base.PipeEndpoint, Base.AbstractPipe, TCPSocket})
         verbose && println("$name position...")
-        @test (s = io(); read!(s, Vector{UInt8}(undef, 4)); position(s))  == 4
+        @test (s = io(); read!(s, Vector{UInt8}(undef, 4)); position(s)) == 4
 
         verbose && println("$name seek...")
         for n = 0:length(text)-1