From 1c2feb02fa8b1a5a8c9f6f091c12eada5e0b0738 Mon Sep 17 00:00:00 2001
From: Mike Danese <mikedanese@google.com>
Date: Mon, 31 Jul 2017 13:14:50 -0700
Subject: [PATCH] gce: make append_or_replace.. atomic

Before this change,
* the final echo is not atomically written to the target file
* two concurrent callers will use the same tempfile
---
 cluster/gce/gci/configure-helper.sh | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/cluster/gce/gci/configure-helper.sh b/cluster/gce/gci/configure-helper.sh
index beaee497d76..cebd8893572 100644
--- a/cluster/gce/gci/configure-helper.sh
+++ b/cluster/gce/gci/configure-helper.sh
@@ -239,10 +239,13 @@ function append_or_replace_prefixed_line {
   local -r file="${1:-}"
   local -r prefix="${2:-}"
   local -r suffix="${3:-}"
+  local -r dirname="$(dirname ${file})"
+  local -r tmpfile="$(mktemp -t filtered.XXXX --tmpdir=${dirname})"
 
   touch "${file}"
-  awk "substr(\$0,0,length(\"${prefix}\")) != \"${prefix}\" { print }" "${file}" > "${file}.filtered"  && mv "${file}.filtered" "${file}"
-  echo "${prefix}${suffix}" >> "${file}"
+  awk "substr(\$0,0,length(\"${prefix}\")) != \"${prefix}\" { print }" "${file}" > "${tmpfile}"
+  echo "${prefix}${suffix}" >> "${tmpfile}"
+  mv "${tmpfile}" "${file}"
 }
 
 function create-node-pki {