osproc.execCmdEx now takes an optional input for stdin

changelog.md

@@ -89,6 +89,8 @@
 - Fix a bug where calling `close` on io streams in osproc.startProcess was a noop and led to
   hangs if a process had both reads from stdin and writes (eg to stdout).
 
+- `osproc.execCmdEx` now takes an optional `input` for stdin.
+
 ## Language changes
 - In newruntime it is now allowed to assign discriminator field without restrictions as long as case object doesn't have custom destructor. Discriminator value doesn't have to be a constant either. If you have custom destructor for case object and you do want to freely assign discriminator fields, it is recommended to refactor object into 2 objects like this:
   ```nim

lib/pure/osproc.nim

@@ -1438,12 +1438,14 @@ elif not defined(useNimRtl):
 
 
 proc execCmdEx*(command: string, options: set[ProcessOption] = {
-                poStdErrToStdOut, poUsePath}): tuple[
+                poStdErrToStdOut, poUsePath}, input = ""): tuple[
                 output: TaintedString,
                 exitCode: int] {.tags:
                 [ExecIOEffect, ReadIOEffect, RootEffect], gcsafe.} =
   ## A convenience proc that runs the `command`, grabs all its output and
-  ## exit code and returns both.
+  ## exit code and returns both. If `input.len > 0`, it is passed as stdin.
+  ## Note: this could block if `input.len` is greater than your OS's maximum
+  ## pipe buffer size.
   ##
   ## See also:
   ## * `execCmd proc <#execCmd,string>`_
@@ -1452,17 +1454,24 @@ proc execCmdEx*(command: string, options: set[ProcessOption] = {
   ## * `execProcess proc
   ##   <#execProcess,string,string,openArray[string],StringTableRef,set[ProcessOption]>`_
   ##
-  ## Example:
-  ##
-  ## .. code-block:: Nim
-  ##  let (outp, errC) = execCmdEx("nim c -r mytestfile.nim")
-
+  runnableExamples:
+    var result = execCmdEx("nim r --hints:off -", options = {}, input = "echo 3*4")
+    import strutils
+    stripLineEnd(result[0])
+    doAssert result == ("12", 0)
+
+  when (NimMajor, NimMinor) < (1, 3):
+    doAssert input.len == 0
   var p = startProcess(command, options = options + {poEvalCommand})
   var outp = outputStream(p)
 
-  # There is no way to provide input for the child process
-  # anymore. Closing it will create EOF on stdin instead of eternal
-  # blocking.
+  if input.len > 0:
+    # There is no way to provide input for the child process
+    # anymore. Closing it will create EOF on stdin instead of eternal
+    # blocking.
+    # Writing in chunks would require a selectors (eg kqueue/epoll) to avoid
+    # blocking on io.
+    inputStream(p).write(input)
   close inputStream(p)
 
   result = (TaintedString"", -1)

tests/stdlib/tosproc.nim

@@ -1,7 +1,7 @@
 # test the osproc module
 
 import stdtest/specialpaths
-import "../.." / compiler/unittest_light
+import "$nim" / compiler/unittest_light
 
 when defined(case_testfile): # compiled test file for child process
   from posix import exitnow
@@ -119,3 +119,8 @@ else:
 
     var result = startProcessTest("nim r --hints:off -", options = {}, input = "echo 3*4")
     doAssert result == ("12\n", 0)
+
+  block execProcessTest:
+    var result = execCmdEx("nim r --hints:off -", options = {}, input = "echo 3*4")
+    stripLineEnd(result[0])
+    doAssert result == ("12", 0)