Issue #21332: Ensure that ``bufsize=1`` in subprocess.Popen() selects line buffering, rather than block buffering.

1 files changed, 12 insertions, 6 deletions

diff --git a/Doc/library/subprocess.rst b/Doc/library/subprocess.rst
index 854993c..b2238f0 100644
--- a/Doc/library/subprocess.rst
+++ b/Doc/library/subprocess.rst
@@ -406,12 +406,18 @@ functions.
 
       Read the `Security Considerations`_ section before using ``shell=True``.
 
-   *bufsize* will be supplied as the corresponding argument to the :func:`open`
-   function when creating the stdin/stdout/stderr pipe file objects: :const:`0`
-   means unbuffered (read and write are one system call and can return short),
-   :const:`1` means line buffered, any other positive value means use a buffer
-   of approximately that size.  A negative bufsize (the default) means the
-   system default of io.DEFAULT_BUFFER_SIZE will be used.
+   *bufsize* will be supplied as the corresponding argument to the
+   :func:`open` function when creating the stdin/stdout/stderr pipe
+   file objects:
+
+   - :const:`0` means unbuffered (read and write are one
+     system call and can return short)
+   - :const:`1` means line buffered
+     (only usable if ``universal_newlines=True`` i.e., in a text mode)
+   - any other positive value means use a buffer of approximately that
+     size
+   - negative bufsize (the default) means the system default of
+     io.DEFAULT_BUFFER_SIZE will be used.
 
    .. versionchanged:: 3.3.1
       *bufsize* now defaults to -1 to enable buffering by default to match the