[pve-devel] appllied: [PATCH] read firstline: only map ENOENT to undef, raise error otherwise

[Thomas Lamprecht <t.lamprecht@proxmox.com>]

Errors like permission denied or I/O ones should bubble up, otherwise
it might hide serious issues and seemingly continue to work, with a
wrong state or the like.

One could argue that the case for not existent should return undef,
while an empty file should return an empty string, but for that we
might want to check all use-sites first.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
---
 src/PVE/Tools.pm | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/PVE/Tools.pm b/src/PVE/Tools.pm
index 174ded8..2d728f8 100644
--- a/src/PVE/Tools.pm
+++ b/src/PVE/Tools.pm
@@ -291,7 +291,10 @@ sub file_read_firstline {
     my ($filename) = @_;
 
     my $fh = IO::File->new ($filename, "r");
-    return undef if !$fh;
+    if (!$fh) {
+	return undef if $! == POSIX::ENOENT;
+	die "file '$filename' exists but open for reading failed - $!\n";
+    }
     my $res = <$fh>;
     chomp $res if $res;
     $fh->close;
-- 
2.39.2