linux-kernel - [PATCH 5.4 205/214] kheaders: remove unneeded cat command piped to head / tail

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Date:   Tue,  1 Sep 2020 17:11:25 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Matthias Maennich <maennich@...gle.com>
Subject: [PATCH 5.4 205/214] kheaders: remove unneeded cat command piped to head / tail

From: Masahiro Yamada <yamada.masahiro@...ionext.com>

commit 9a066357184485784f782719093ff804d05b85db upstream.

The 'head' and 'tail' commands can take a file path directly.
So, you do not need to run 'cat'.

  cat kernel/kheaders.md5 | head -1

... is equivalent to:

  head -1 kernel/kheaders.md5

and the latter saves forking one process.

While I was here, I replaced 'head -1' with 'head -n 1'.

I also replaced '==' with '=' since we do not have a good reason to
use the bashism.

Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
Signed-off-by: Matthias Maennich <maennich@...gle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/gen_kheaders.sh |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/kernel/gen_kheaders.sh
+++ b/kernel/gen_kheaders.sh
@@ -41,10 +41,10 @@ obj_files_md5="$(find $dir_list -name "*
 this_file_md5="$(ls -l $sfile | md5sum | cut -d ' ' -f1)"
 if [ -f $tarfile ]; then tarfile_md5="$(md5sum $tarfile | cut -d ' ' -f1)"; fi
 if [ -f kernel/kheaders.md5 ] &&
-	[ "$(cat kernel/kheaders.md5|head -1)" == "$src_files_md5" ] &&
-	[ "$(cat kernel/kheaders.md5|head -2|tail -1)" == "$obj_files_md5" ] &&
-	[ "$(cat kernel/kheaders.md5|head -3|tail -1)" == "$this_file_md5" ] &&
-	[ "$(cat kernel/kheaders.md5|tail -1)" == "$tarfile_md5" ]; then
+	[ "$(head -n 1 kernel/kheaders.md5)" = "$src_files_md5" ] &&
+	[ "$(head -n 2 kernel/kheaders.md5 | tail -n 1)" = "$obj_files_md5" ] &&
+	[ "$(head -n 3 kernel/kheaders.md5 | tail -n 1)" = "$this_file_md5" ] &&
+	[ "$(tail -n 1 kernel/kheaders.md5)" = "$tarfile_md5" ]; then
 		exit
 fi