Mention how stdio handling works

[etc/vim.git] / README.md

diff --git a/README.md b/README.md
index 0978887264ba57f898cbb6cd1fe60f4fefbdc30e..20ab4be7e5b3c728d8cf6863563ac34e3d4fd22a 100644 (file)
--- a/README.md
+++ b/README.md
@@ -54,6 +54,12 @@ Options:
   --help                      Show this message and exit.
 ```
 
+`Black` is a well-behaved Unix-style command-line tool:
+* it does nothing if no sources are passed to it;
+* it will read from standard input and write to standard output if `-`
+  is used as the filename;
+* it only outputs messages to users on standard error.
+
 
 ## The philosophy behind *Black*
 
@@ -76,12 +82,14 @@ or simple statement per line.  If this fits the allotted line length,
 great.
 ```py3
 # in:
+
 l = [1,
      2,
      3,
 ]
 
 # out:
+
 l = [1, 2, 3]
 ```
 
@@ -89,9 +97,11 @@ If not, *Black* will look at the contents of the first outer matching
 brackets and put that in a separate indented line.
 ```py3
 # in:
+
 l = [[n for n in list_bosses()], [n for n in list_employees()]]
 
 # out:
+
 l = [
     [n for n in list_bosses()], [n for n in list_employees()]
 ]
@@ -106,12 +116,14 @@ matching brackets.  If that doesn't work, it will put all of them in
 separate lines.
 ```py3
 # in:
+
 def very_important_function(template: str, *variables, file: os.PathLike, debug: bool = False):
     """Applies `variables` to the `template` and writes to `file`."""
     with open(file, 'w') as f:
         ...
 
 # out:
+
 def very_important_function(
     template: str,
     *variables,
@@ -203,6 +215,12 @@ body.
 
 * Visual Studio Code: [joslarson.black-vscode](https://marketplace.visualstudio.com/items?itemName=joslarson.black-vscode)
 
+Any tool that can pipe code through *Black* using its stdio mode (just
+[use `-` as the file name](http://www.tldp.org/LDP/abs/html/special-chars.html#DASHREF2)).
+The formatted code will be returned on stdout (unless `--check` was
+passed).  *Black* will still emit messages on stderr but that shouldn't
+affect your use case.
+
 There is currently no integration with any other text editors. Vim and
 Atom/Nuclide integration is planned by the author, others will require
 external contributions.