[PATCH v2 1/3] simplify updating GRUB_CMDLINE_LINUX in GRUB_ETC_DEFAULT

[Coiby Xu]

Use sed command group and conditional control to get rid of grep.

Suggested-by: Philipp Rudo <prudo(a)redhat.com&gt;
Signed-off-by: Coiby Xu <coxu(a)redhat.com&gt;
---
 kdumpctl | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/kdumpctl b/kdumpctl
index 9fd76ac..998ac6e 100755
--- a/kdumpctl
+++ b/kdumpctl
@@ -1405,19 +1405,22 @@ GRUB_ETC_DEFAULT="/etc/default/grub"
 # $2: new value. If empty, the parameter would be removed
 _update_kernel_cmdline_in_grub_etc_default()
 {
-	local _para=$1 _val=$2 _para_val _regex
+	local _para=$1 _val=$2 _para_val
 
 	if [[ -n $_val ]]; then
 		_para_val="$_para=$_val"
 	fi
 
-	_regex='^(GRUB_CMDLINE_LINUX=.*)([[:space:]"])'"$_para"'=[^[:space:]"]*(.*)$'
-	if grep -q -E "$_regex" "$GRUB_ETC_DEFAULT"; then
-		sed -i -E
's/'"$_regex"'/\1\2'"$_para_val"'\3/'
"$GRUB_ETC_DEFAULT"
-	elif [[ -n $_para_val ]]; then
-		# If the kernel parameter doesn't exist, put it in the first
-		sed -i -E 's/^(GRUB_CMDLINE_LINUX=")/\1'"$_para_val"' /'
"$GRUB_ETC_DEFAULT"
-	fi
+	# If the parameter already exists, replace it with new value.
+	# Otherwise insert it to the end.
+	sed -i -E "/^GRUB_CMDLINE_LINUX=/ {
+	          
s/([[:space:]\"])crashkernel=[^[:space:]\"]*(.*)$/\1${_para_val}\2/;
+	           # t: jump to a label only if a s/// command has succeeded.
+	           #    Since there is no label, it would jump to the end i.e.
+	           #    skip the last command if the parameter already exist
+	           t;
+	           s/\"$/ ${_para_val}\"/
+          }" "$GRUB_ETC_DEFAULT"
 }
 
 reset_crashkernel()
-- 
2.34.1