| Message ID | 20241119014339.3640843-1-dominique.martinet@atmark-techno.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | btrfs-progs: utils: ask_user: flush stdout after prompt | expand |
在 2024/11/19 12:13, Dominique Martinet 写道: > when stdio is line buffered printf will not flush anything (on musl?), > leaving the program hanging without displaying any prompt and weird > dialogs such as the following: > ``` > alpine:~# btrfstune -S 0 /dev/mmcblk1p1 > WARNING: this is dangerous, clearing the seeding flag may cause the derived device not to be mountable! > y > WARNING: seeding flag is not set on /dev/mmcblk1p1 > We are going to clear the seeding flag, are you sure? [y/N]: alpine:~# > ``` > > forcing flush makes the prompt display properly > > Signed-off-by: Dominique Martinet <dominique.martinet@atmark-techno.com> Reviewed-by: Qu Wenruo <wqu@suse.com> Thanks, Qu > --- > > I don't think this behaviour is musl-specific, but it seems odd this was > never reported before.. perhaps glibc flushes on fgets? > Anyway, it's easy to fix and there is probably no downside so here's a patch. > > I've tested it works as expected, e.g. prompt is now properly displayed > before waiting for input. > > common/utils.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/common/utils.c b/common/utils.c > index 3ca7cff396fe..9515abd47af8 100644 > --- a/common/utils.c > +++ b/common/utils.c > @@ -416,6 +416,7 @@ int ask_user(const char *question) > char *answer; > > printf("%s [y/N]: ", question); > + fflush(stdout); > > return fgets(buf, sizeof(buf) - 1, stdin) && > (answer = strtok_r(buf, " \t\n\r", &saveptr)) && > -- > 2.39.5 > > >
diff --git a/common/utils.c b/common/utils.c index 3ca7cff396fe..9515abd47af8 100644 --- a/common/utils.c +++ b/common/utils.c @@ -416,6 +416,7 @@ int ask_user(const char *question) char *answer; printf("%s [y/N]: ", question); + fflush(stdout); return fgets(buf, sizeof(buf) - 1, stdin) && (answer = strtok_r(buf, " \t\n\r", &saveptr)) &&
when stdio is line buffered printf will not flush anything (on musl?), leaving the program hanging without displaying any prompt and weird dialogs such as the following: ``` alpine:~# btrfstune -S 0 /dev/mmcblk1p1 WARNING: this is dangerous, clearing the seeding flag may cause the derived device not to be mountable! y WARNING: seeding flag is not set on /dev/mmcblk1p1 We are going to clear the seeding flag, are you sure? [y/N]: alpine:~# ``` forcing flush makes the prompt display properly Signed-off-by: Dominique Martinet <dominique.martinet@atmark-techno.com> --- I don't think this behaviour is musl-specific, but it seems odd this was never reported before.. perhaps glibc flushes on fgets? Anyway, it's easy to fix and there is probably no downside so here's a patch. I've tested it works as expected, e.g. prompt is now properly displayed before waiting for input. common/utils.c | 1 + 1 file changed, 1 insertion(+) -- 2.39.5