add utility functions.

* git-difme.scm (with-directory-excursion): new macro. verbatim
from (guix build utils). thank you ludovic courtès.
(difme-exec): new function.

1 files changed, 29 insertions, 1 deletions

diff --git a/git-difme.scm b/git-difme.scm
index e5d509a..76c35e2 100644
--- a/git-difme.scm
+++ b/git-difme.scm
@@ -2,6 +2,34 @@
 ;; license: gnu gpl version 3 or higher.
 ;; copyright 2016 rsiddharth <s@ricketyspace.net>
 
-;; main function.
+(define-module (git-difme)
+  #:use-module (ice-9 popen)
+  #:use-module (ice-9 rdelim)
+  #:export (main))
+
+;;;; utils
+
+;;; following macro from (guix build utils) module.
+;;; copyright 2012 Ludovic Courtès <ludo@gnu.org>
+;;; commit b0e0d0e99f
+
+(define-syntax-rule (with-directory-excursion dir body ...)
+  "run BODY with DIR as the process's current directory."
+  (let ((init (getcwd)))
+    (dynamic-wind
+      (lambda () (chdir dir))
+      (lambda () body ...)
+      (lambda () (chdir init)))))
+
+(define (difme-exec cmd)
+  "execute CMD and return output as a list of strings."
+  (let* ((port (open-input-pipe cmd))
+         (out (read-string port))
+         (out-lst (map string-trim-both
+                       (delete "" (string-split out #\newline)))))
+    (close-pipe port)
+    out-lst))
+
+;;;; main
 (define (main srcs)
   srcs)