Merge branch 'master' into core-updates

1 files changed, 16 insertions, 0 deletions

diff --git a/guix/utils.scm b/guix/utils.scm
index b730340eda..04a74ee29a 100644
--- a/guix/utils.scm
+++ b/guix/utils.scm
@@ -67,6 +67,7 @@
             file-extension
             file-sans-extension
             call-with-temporary-output-file
+            with-atomic-file-output
             fold2
             filtered-port))
 
@@ -426,6 +427,21 @@ call."
         (false-if-exception (close out))
         (false-if-exception (delete-file template))))))
 
+(define (with-atomic-file-output file proc)
+  "Call PROC with an output port for the file that is going to replace FILE.
+Upon success, FILE is atomically replaced by what has been written to the
+output port, and PROC's result is returned."
+  (let* ((template (string-append file ".XXXXXX"))
+         (out      (mkstemp! template)))
+    (with-throw-handler #t
+      (lambda ()
+        (let ((result (proc out)))
+          (close out)
+          (rename-file template file)
+          result))
+      (lambda (key . args)
+        (false-if-exception (delete-file template))))))
+
 (define fold2
   (case-lambda
     ((proc seed1 seed2 lst)