Support standard input, output and error streamsfeature/stdout-stderr-stream

* doc/lispref/streams.texi: Update doc
* lisp/simple.el (external-standard-input): New function
* src/fns.c (external-standard-input-read-char,
  external-standard-input-read-line): New functions
* src/print.c: (external-standard-output,
  external-standard-input): New functions

2 files changed, 81 insertions, 0 deletions

diff --git a/src/fns.c b/src/fns.c
index c318608e4ce..72a7e3ab820 100644
--- a/src/fns.c
+++ b/src/fns.c
@@ -5082,6 +5082,65 @@ If nil, use the current buffer." */ )
   return make_digest_string (digest, SHA1_DIGEST_SIZE);
 }
 
+DEFUN ("external-standard-input-read-char",Fexternal_standard_input_read_char, Sexternal_standard_input_read_char, 0, 0, 0,
+       doc: /* Read a single character from the system standard input.
+
+Returns -1 if standard input is at the end.*/)
+     (void)
+{
+  int c;
+  Lisp_Object val;
+
+  c = getchar();
+  XSETINT(val,c);
+
+  return val;
+}
+
+DEFUN ("external-standard-input-read-line", Fexternal_standard_input_read_line, Sexternal_standard_input_read_line, 0, 0, 0,
+      doc: /* Read a line from the system standard input.*/)
+  (void)
+{
+  ptrdiff_t size, len;
+  char *line;
+  Lisp_Object val;
+  int c;
+
+  val = Qnil;
+  size = 100;
+  len = 0;
+  line = xmalloc (size);
+
+  while ((c = getchar ()) != '\n' && c != '\r')
+    {
+      if (c == EOF)
+        {
+          if (errno != 0)
+            break;
+        }
+      else
+        {
+          if (len == size)
+            line = xpalloc (line, &size, 1, -1, sizeof *line);
+          line[len++] = c;
+        }
+    }
+
+  if (len || c == '\n' || c == '\r')
+    {
+      val = make_string (line, len);
+      xfree (line);
+    }
+  else
+    {
+      xfree (line);
+      error ("Error reading from stdin");
+    }
+
+  return val;
+}
+
+
 
 void
 syms_of_fns (void)
@@ -5249,4 +5308,7 @@ this variable.  */);
   defsubr (&Ssecure_hash);
   defsubr (&Sbuffer_hash);
   defsubr (&Slocale_info);
+  defsubr (&Sexternal_standard_input_read_char);
+  defsubr (&Sexternal_standard_input_read_line);
+
 }
diff --git a/src/print.c b/src/print.c
index 5531210e1b8..25f0afbf972 100644
--- a/src/print.c
+++ b/src/print.c
@@ -769,6 +769,22 @@ to make it write to the debugging output.  */)
   return character;
 }
 
+DEFUN ("external-standard-output", Fexternal_standard_output, Sexternal_standard_output, 1, 1, 0,
+       doc: /* Output character CHARACTER to system standard output. */)
+     (Lisp_Object character)
+{
+  CHECK_NUMBER (character);
+  printchar_to_stream (XINT(character), stdout);
+  return character;
+}
+
+DEFUN ("external-standard-error", Fexternal_standard_error, Sexternal_standard_error, 1, 1, 0,
+       doc: /* Output character CHARACTER to system standard error. */)
+     (Lisp_Object character)
+{
+  return Fexternal_debugging_output (character);
+}
+
 /* This function is never called.  Its purpose is to prevent
    print_output_debug_flag from being optimized away.  */
 
@@ -2307,7 +2323,10 @@ priorities.  */);
   defsubr (&Sprinc);
   defsubr (&Sprint);
   defsubr (&Sterpri);
+  defsubr (&Sexternal_standard_output);
+  defsubr (&Sexternal_standard_error);
   defsubr (&Swrite_char);
+
   defsubr (&Sredirect_debugging_output);
 
   DEFSYM (Qprint_escape_newlines, "print-escape-newlines");