[PATCH] progress: no progress in background

[Luke Mewburn]

Disable the display of the progress if stderr is not the
current foreground process.
Still display the final result when done.

Signed-off-by: Luke Mewburn <l...@mewburn.net>
Acked-by: Nicolas Pitre <n...@fluxnic.net>
---
 progress.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/progress.c b/progress.c
index 412e6b1..43d9228 100644
--- a/progress.c
+++ b/progress.c
@@ -72,6 +72,11 @@ static void clear_progress_signal(void)
        progress_update = 0;
 }
 
+static int is_foreground_fd(int fd)
+{
+       return getpgid(0) == tcgetpgrp(fd);
+}
+
 static int display(struct progress *progress, unsigned n, const char *done)
 {
        const char *eol, *tp;
@@ -98,16 +103,21 @@ static int display(struct progress *progress, unsigned n, 
const char *done)
                unsigned percent = n * 100 / progress->total;
                if (percent != progress->last_percent || progress_update) {
                        progress->last_percent = percent;
-                       fprintf(stderr, "%s: %3u%% (%u/%u)%s%s",
-                               progress->title, percent, n,
-                               progress->total, tp, eol);
-                       fflush(stderr);
+                       if (is_foreground_fd(fileno(stderr)) || done) {
+                               fprintf(stderr, "%s: %3u%% (%u/%u)%s%s",
+                                       progress->title, percent, n,
+                                       progress->total, tp, eol);
+                               fflush(stderr);
+                       }
                        progress_update = 0;
                        return 1;
                }
        } else if (progress_update) {
-               fprintf(stderr, "%s: %u%s%s", progress->title, n, tp, eol);
-               fflush(stderr);
+               if (is_foreground_fd(fileno(stderr)) || done) {
+                       fprintf(stderr, "%s: %u%s%s",
+                               progress->title, n, tp, eol);
+                       fflush(stderr);
+               }
                progress_update = 0;
                return 1;
        }
-- 
2.3.5.1.g63ef1a0

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