ambrevar/shell: Add cmd<>, cmd< and $cmd<.

.local/share/common-lisp/source/ambrevar/shell.lisp

@@ -247,7 +247,7 @@ List of background process is maintained in `*process-list*'."
     handle))
 
 (export-always 'cmd>)
-(defun cmd> (cmd &rest args) ; TODO: "|" is not convenient in CL, use "/" or "-"?
+(defun cmd> (cmd &rest args) ; TODO: "|" is not convenient in CL, use "/" or "-"?  See `cmd<>'.
   "Like `cmd:cmd&' but return the output as a stream.
 Return the process handler as second value.
 Use
@@ -260,6 +260,42 @@ to get the final output as a string."
     (values (uiop:process-info-output handler)
             handler)))
 
+(export-always 'cmd<>)
+(defun cmd<> (cmd &rest args)
+  "Like `cmd>' but last argument is passed as `:input'.
+This can be usefully chained, e.g. with arrow macros.
+Example:
+
+  (->>
+    (cmd> \"cat\" \".../share/hunspell/en_GB-large.dic\")
+    (cmd<> \"sort\")
+    (cmd<> \"uniq\" \"-c\")
+    (cmd<> \"sort\" \"-nr\")
+    (cmd<> \"head\" \"-3\"))"
+  (let* ((butlast-args (butlast args))
+         (last-arg (first (last args)))
+         (handler (apply #'cmd:cmd& cmd (append butlast-args
+                                                (list :output :stream
+                                                      :input last-arg)))))
+    (values (uiop:process-info-output handler)
+            handler)))
+
+(export-always 'cmd<)
+(defun cmd< (cmd &rest args)
+  "Like `cmd<>' but output to standard output."
+  (let* ((butlast-args (butlast args))
+         (last-arg (first (last args))))
+    (apply #'cmd:cmd cmd (append butlast-args
+                                 (list :input last-arg)))))
+
+(export-always '$cmd<)
+(defun $cmd< (cmd &rest args)
+  "Like `cmd<>' but return string."
+  (let* ((butlast-args (butlast args))
+         (last-arg (first (last args))))
+    (apply #'cmd:$cmd cmd (append butlast-args
+                                  (list :input last-arg)))))
+
 (export-always 'tee)
 (defun tee (input-stream)
   "Return the INPUT-STREAM and its string representation as a second value."