processes: Add '--format' and the "normalized" format.

* guix/scripts/processes.scm (lock->recutils): New procedure.
(daemon-session->recutils): Use it.
(daemon-sessions->recutils, session-key->recutils)
(session-scalars->normalized-record)
(child-process->normalized-record)
(daemon-sessions->normalized-record): New procedures.
(session-rec-type, lock-rec-type, child-process-rec-type)
(%available-formats): New variables.
(list-formats): New procedure.
(%options, show-help): Add '--format'.
(%default-options): New variable.
(guix-processes): Use 'parse-command-line' instead of 'args-fold*'.
Honor the 'format' value in OPTIONS.
* doc/guix.texi (Invoking guix processes): Document '--format'.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

2 files changed, 166 insertions, 19 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index 7cef2371ad..e7277fc9ee 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -12899,6 +12899,45 @@ ClientPID: 19419
 ClientCommand: cuirass --cache-directory /var/cache/cuirass @dots{}
 @end example
 
+Additional options are listed below.
+
+@table @code
+@item --format=@var{format}
+@itemx -f @var{format}
+Produce output in the specified @var{format}, one of:
+
+@table @code
+@item recutils
+The default option. It outputs a set of Session recutils records
+that include each @code{ChildProcess} as a field.
+
+@item normalized
+Normalize the output records into record sets (@pxref{Record Sets,,,
+recutils, GNU recutils manual}).  Normalizing into record sets allows
+joins across record types.  The example below lists the PID of each
+@code{ChildProcess} and the associated PID for @code{Session} that
+spawned the @code{ChildProcess} where the @code{Session} was started
+using @command{guix build}.
+
+@example
+$ guix processes --format=normalized | \
+    recsel \
+    -j Session \
+    -t ChildProcess \
+    -p Session.PID,PID \
+    -e 'Session.ClientCommand ~ "guix build"'
+PID: 4435
+Session_PID: 4278
+
+PID: 4554
+Session_PID: 4278
+
+PID: 4646
+Session_PID: 4278
+@end example
+@end table
+@end table
+
 @node System Configuration
 @chapter System Configuration
 
diff --git a/guix/scripts/processes.scm b/guix/scripts/processes.scm
index 3a7ea0b89c..3db5603286 100644
--- a/guix/scripts/processes.scm
+++ b/guix/scripts/processes.scm
@@ -177,6 +177,9 @@ active sessions, and the master 'guix-daemon' process."
     (values (filter-map child-process->session children)
             master)))
 
+(define (lock->recutils lock port)
+  (format port "LockHeld: ~a~%" lock))
+
 (define (daemon-session->recutils session port)
   "Display SESSION information in recutils format on PORT."
   (format port "SessionPID: ~a~%"
@@ -185,8 +188,7 @@ active sessions, and the master 'guix-daemon' process."
           (process-id (daemon-session-client session)))
   (format port "ClientCommand:~{ ~a~}~%"
           (process-command (daemon-session-client session)))
-  (for-each (lambda (lock)
-              (format port "LockHeld: ~a~%" lock))
+  (for-each (lambda (lock) (lock->recutils lock port))
             (daemon-session-locks-held session))
   (for-each (lambda (process)
               (format port "ChildPID: ~a~%"
@@ -195,19 +197,102 @@ active sessions, and the master 'guix-daemon' process."
                       (process-command process)))
             (daemon-session-children session)))
 
+(define (daemon-sessions->recutils port sessions)
+  "Display denormalized SESSIONS information to PORT."
+  (for-each (lambda (session)
+              (daemon-session->recutils session port)
+              (newline port))
+            sessions))
+
+(define session-rec-type
+  "%rec: Session
+%type: PID int
+%type: ClientPID int
+%key: PID
+%mandatory: ClientPID ClientCommand")
+
+(define lock-rec-type
+  "%rec: Lock
+%mandatory: LockHeld
+%type: Session rec Session")
+
+(define child-process-rec-type
+  "%rec: ChildProcess
+%type: PID int
+%type: Session rec Session
+%key: PID
+%mandatory: Command")
+
+(define (session-key->recutils session port)
+  "Display SESSION PID as a recutils field on PORT."
+  (format
+   port "Session: ~a"
+   (process-id (daemon-session-process session))))
+
+(define (session-scalars->normalized-record session port)
+  "Display SESSION scalar fields to PORT in normalized form."
+  (format port "PID: ~a~%"
+          (process-id (daemon-session-process session)))
+  (format port "ClientPID: ~a~%"
+          (process-id (daemon-session-client session)))
+  (format port "ClientCommand:~{ ~a~}~%"
+          (process-command (daemon-session-client session))))
+
+(define (child-process->normalized-record process port)
+  "Display PROCESS record on PORT in normalized form"
+  (format port "PID: ~a" (process-id process))
+  (newline port)
+  (format port "Command:~{ ~a~}" (process-command process)))
+
+(define (daemon-sessions->normalized-record port sessions)
+  "Display SESSIONS recutils on PORT in normalized form"
+  (display session-rec-type port)
+  (newline port)
+  (newline port)
+  (for-each (lambda (session)
+              (session-scalars->normalized-record session port)
+              (newline port))
+            sessions)
+
+  (display lock-rec-type port)
+  (newline port)
+  (newline port)
+  (for-each (lambda (session)
+              (for-each (lambda (lock)
+                          (lock->recutils "testing testing" port)
+                          (session-key->recutils session port)
+                          (newline port)
+                          (newline port))
+                        (daemon-session-locks-held session)))
+            sessions)
+
+  (display child-process-rec-type port)
+  (newline port)
+  (newline port)
+  (for-each (lambda (session)
+              (for-each (lambda (process)
+                          (child-process->normalized-record process port)
+                          (newline port)
+                          (session-key->recutils session port)
+                          (newline port)
+                          (newline port))
+                        (daemon-session-children session)))
+            sessions))
+
 
 ;;;
 ;;; Options.
 ;;;
 
-(define %options
-  (list (option '(#\h "help") #f #f
-                (lambda args
-                  (show-help)
-                  (exit 0)))
-        (option '(#\V "version") #f #f
-                (lambda args
-                  (show-version-and-exit "guix processes")))))
+(define %available-formats
+  '("recutils" "normalized"))
+
+(define (list-formats)
+  (display (G_ "The available formats are:\n"))
+  (newline)
+  (for-each (lambda (f)
+              (format #t "  - ~a~%" f))
+            %available-formats))
 
 (define (show-help)
   (display (G_ "Usage: guix processes
@@ -218,8 +303,33 @@ List the current Guix sessions and their processes."))
   (display (G_ "
   -V, --version          display version information and exit"))
   (newline)
+  (display (G_ "
+  -f, --format=FORMAT    display results as normalized record sets"))
+  (display (G_ "
+      --list-formats     display available formats"))
+  (newline)
   (show-bug-report-information))
 
+(define %options
+  (list (option '(#\h "help") #f #f
+                (lambda args
+                  (show-help)
+                  (exit 0)))
+        (option '(#\V "version") #f #f
+                (lambda args
+                  (show-version-and-exit "guix processes")))
+        (option '(#\f "format") #t #f
+                (lambda (opt name arg result)
+                  (unless (member arg %available-formats)
+                    (leave (G_ "~a: unsupported output format~%") arg))
+                  (alist-cons 'format (string->symbol arg) result)))
+        (option '("list-formats") #f #f
+                (lambda (opt name arg result)
+                  (list-formats)
+                  (exit 0)))))
+
+(define %default-options '((format . recutils)))
+
 
 ;;;
 ;;; Entry point.
@@ -228,18 +338,16 @@ List the current Guix sessions and their processes."))
 (define-command (guix-processes . args)
   (category plumbing)
   (synopsis "list currently running sessions")
+
   (define options
-    (args-fold* args %options
-                (lambda (opt name arg result)
-                  (leave (G_ "~A: unrecognized option~%") name))
-                cons
-                '()))
+    (parse-command-line args %options (list %default-options)
+                        #:build-options? #f))
 
   (with-paginated-output-port port
-    (for-each (lambda (session)
-                (daemon-session->recutils session port)
-                (newline port))
-              (daemon-sessions))
+    (match (assoc-ref options 'format)
+      ('normalized
+       (daemon-sessions->normalized-record port (daemon-sessions)))
+      (_ (daemon-sessions->recutils port (daemon-sessions))))
 
     ;; Pass 'R' (instead of 'r') so 'less' correctly estimates line length.
     #:less-options "FRX"))