Document process-send/recv.

doc/utils.md

@@ -158,6 +158,16 @@ UTF-8 BOM, removes it.
 Returns a list of strings representing all the lines produced by
 running the command given.
 
+    (process-send/recv cmd args . lines)
+
+* ```cmd``` - a string with command
+* ```args``` - list of arguments
+* ```lines``` - lines to feed to stdin of the process
+
+Executes given command ```cmd``` with given argument list ```args```
+writing all ```lines``` to its standard input and then reads all the
+process output.
+
 ### List
 
     (import util-list)