Merge branch 'maint-20' into maint

* maint-20:
  Updated OTP version
  Update release notes
  Update version numbers
  erts: Add system_flags(erts_alloc,"+M?sbct *")
  erts: Add age order first fit allocator strategies
  erts: Refactor erl_ao_firstfit_alloc
  erts: Add migration options "acnl" and "acfml"
  kernel: Add os:cmd/2 with max_size option
  erts: Add more stats for mbcs_pool
  erts: Fix alloc_SUITE:migration
  stdlib: Make ets_SUITE memory check try again
  erts: Improve carrier pool search
  erts: Improve alloc_SUITE:migration
  erts: Refactor carrier dealloc migration

2 files changed, 58 insertions, 5 deletions

diff --git a/lib/kernel/doc/src/notes.xml b/lib/kernel/doc/src/notes.xml
index d7f224c38e..65fe9b9c07 100644
--- a/lib/kernel/doc/src/notes.xml
+++ b/lib/kernel/doc/src/notes.xml
@@ -31,6 +31,26 @@
   </header>
   <p>This document describes the changes made to the Kernel application.</p>
 
+<section><title>Kernel 5.4.2</title>
+
+    <section><title>Fixed Bugs and Malfunctions</title>
+      <list>
+        <item>
+          <p>
+	    Add <c>os:cmd/2</c> that takes an options map as the
+	    second argument.</p>
+          <p>
+	    Add <c>max_size</c> as an option to <c>os:cmd/2</c> that
+	    control the maximum size of the result that
+	    <c>os:cmd/2</c> will return.</p>
+          <p>
+	    Own Id: OTP-14823</p>
+        </item>
+      </list>
+    </section>
+
+</section>
+
 <section><title>Kernel 5.4.1</title>
 
     <section><title>Fixed Bugs and Malfunctions</title>
diff --git a/lib/kernel/doc/src/os.xml b/lib/kernel/doc/src/os.xml
index 0e9add4161..7ce2f54542 100644
--- a/lib/kernel/doc/src/os.xml
+++ b/lib/kernel/doc/src/os.xml
@@ -38,17 +38,35 @@
       most platforms.</p>
   </description>
 
+  <datatypes>
+    <datatype>
+      <name name="os_command"/>
+    </datatype>
+    <datatype>
+      <name name="os_command_opts"/>
+      <desc>
+        <p>Options for <seealso marker="#cmd/2"><c>os:cmd/2</c></seealso></p>
+        <taglist>
+          <tag><c>max_size</c></tag>
+          <item>
+            <p>The maximum size of the data returned by the <c>os:cmd</c> call.
+            See the <seealso marker="#cmd/2"><c>os:cmd/2</c></seealso>
+            documentation for more details.</p>
+          </item>
+        </taglist>
+      </desc>
+    </datatype>
+  </datatypes>
+
   <funcs>
     <func>
       <name name="cmd" arity="1"/>
+      <name name="cmd" arity="2"/>
       <fsummary>Execute a command in a shell of the target OS.</fsummary>
       <desc>
         <p>Executes <c><anno>Command</anno></c> in a command shell of the
-          target OS,
-          captures the standard output of the command, and returns this
-          result as a string. This function is a replacement of
-          the previous function <c>unix:cmd/1</c>; they are equivalent on a
-          Unix platform.</p>
+          target OS, captures the standard output of the command,
+          and returns this result as a string.</p>
         <p><em>Examples:</em></p>
         <code type="none">
 LsOut = os:cmd("ls"), % on unix platform
@@ -57,6 +75,21 @@ DirOut = os:cmd("dir"), % on Win32 platform</code>
           called from another program (for example, <c>os:cmd/1</c>)
           can differ, compared with the standard output of the command
           when called directly from an OS command shell.</p>
+        <p><c>os:cmd/2</c> was added in kernel-5.5 (OTP-20.2.1). It makes it
+          possible to pass an options map as the second argument in order to
+          control the behaviour of <c>os:cmd</c>. The possible options are:
+        </p>
+        <taglist>
+          <tag><c>max_size</c></tag>
+          <item>
+            <p>The maximum size of the data returned by the <c>os:cmd</c> call.
+              This option is a safety feature that should be used when the command
+              executed can return a very large, possibly infinite, result.</p>
+            <code type="none">
+> os:cmd("cat /dev/zero", #{ max_size => 20 }).
+[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]</code>
+          </item>
+        </taglist>
       </desc>
     </func>