bash scripts: remove useless cat

Some `cat` calls are useless, remove them to make it cleaner.
See: https://github.com/koalaman/shellcheck/wiki/SC2002

Signed-off-by: Kairui Song <kasong@redhat.com>
Acked-by: Philipp Rudo <prudo@redhat.com>

dracut-module-setup.sh

@@ -114,7 +114,7 @@ kdump_setup_dns() {
         _dns=$(echo $_nameserver | cut -d' ' -f2)
         [ -z "$_dns" ] && continue
 
-        if [ ! -f $_dnsfile ] || [ ! $(cat $_dnsfile | grep -q $_dns) ]; then
+        if [ ! -f $_dnsfile ] || ! grep -q "$_dns" "$_dnsfile" ; then
             echo "nameserver=$_dns" >> "$_dnsfile"
         fi
     done < "/etc/resolv.conf"
@@ -988,7 +988,9 @@ kdump_configure_fence_kdump () {
 # Install a random seed used to feed /dev/urandom
 # By the time kdump service starts, /dev/uramdom is already fed by systemd
 kdump_install_random_seed() {
-    local poolsize=`cat /proc/sys/kernel/random/poolsize`
+    local poolsize
+
+    poolsize=$(</proc/sys/kernel/random/poolsize)
 
     if [ ! -d ${initdir}/var/lib/ ]; then
         mkdir -p ${initdir}/var/lib/

kdumpctl

@@ -204,8 +204,8 @@ restore_default_initrd()
 	# fadump to kdump. Restore the original default initrd.
 	if [ -f $DEFAULT_INITRD_BAK ] && [ -f $INITRD_CHECKSUM_LOCATION ]; then
 		# verify checksum before restoring
-		backup_checksum=`sha1sum $DEFAULT_INITRD_BAK | awk '{ print $1 }'`
-		default_checksum=`cat $INITRD_CHECKSUM_LOCATION | awk '{ print $1 }'`
+		backup_checksum=$(sha1sum "$DEFAULT_INITRD_BAK" | awk '{ print $1 }')
+		default_checksum=$(awk '{ print $1 }' "$INITRD_CHECKSUM_LOCATION")
 		if [ "$default_checksum" != "$backup_checksum" ]; then
 			dwarn "WARNING: checksum mismatch! Can't restore original initrd.."
 		else
@@ -638,8 +638,7 @@ function load_kdump_kernel_key()
                 return
         fi
 
-        KDUMP_KEY_ID=$(cat /usr/share/doc/kernel-keys/$KDUMP_KERNELVER/kernel-signing-ppc.cer |
-                        keyctl padd asymmetric kernelkey-$RANDOM %:.ima)
+        KDUMP_KEY_ID=$(keyctl padd asymmetric kernelkey-$RANDOM %:.ima < "/usr/share/doc/kernel-keys/$KDUMP_KERNELVER/kernel-signing-ppc.cer")
 }
 
 # remove a previously loaded key. There's no real security implication
@@ -832,8 +831,11 @@ propagate_ssh_key()
 
 show_reserved_mem()
 {
-    local mem=$(cat /sys/kernel/kexec_crash_size)
-    local mem_mb=$(expr $mem / 1024 / 1024)
+    local mem
+    local mem_mb
+
+    mem=$(</sys/kernel/kexec_crash_size)
+    mem_mb=$(expr "$mem" / 1024 / 1024)
 
     dinfo "Reserved "$mem_mb"MB memory for crash kernel"
 }
@@ -841,8 +843,8 @@ show_reserved_mem()
 check_current_fadump_status()
 {
 	# Check if firmware-assisted dump has been registered.
-	rc=`cat $FADUMP_REGISTER_SYS_NODE`
-	[ $rc -eq 1 ] && return 0
+	rc=$(<$FADUMP_REGISTER_SYS_NODE)
+	[[ $rc -eq 1 ]] && return 0
 	return 1
 }
 
@@ -1259,7 +1261,7 @@ do_estimate() {
 	# The default pre-reserved crashkernel value
 	baseline_size=$((baseline * size_mb))
 	# Current reserved crashkernel size
-	reserved_size=$(cat /sys/kernel/kexec_crash_size)
+	reserved_size=$(</sys/kernel/kexec_crash_size)
 	# A pre-estimated value for userspace usage and kernel
 	# runtime allocation, 64M should good for most cases
 	runtime_size=$((64 * size_mb))

mkdumprd

@@ -331,7 +331,7 @@ is_unresettable()
 
     if [ -f "$path" ]
     then
-        resettable="$(cat $path)"
+        resettable="$(<"$path")"
         [ $resettable -eq 0 -a "$OVERRIDE_RESETTABLE" -eq 0 ] && {
             local device=$(udevadm info --query=all --path=/sys/dev/block/$1 | awk -F= '/DEVNAME/{print $2}')
             derror "Error: Can not save vmcore because device $device is unresettable"