linux-kernel - [PATCH 1/5] kheaders: remove unneeded 'cat' command piped to 'head' / 'tail'

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Message-Id: <20191008120556.4263-1-yamada.masahiro@socionext.com>
Date:   Tue,  8 Oct 2019 21:05:52 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     linux-kbuild@...r.kernel.org
Cc:     Greg KH <gregkh@...uxfoundation.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/5] kheaders: remove unneeded 'cat' command piped to 'head' / 'tail'

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>
---

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

diff --git a/kernel/gen_kheaders.sh b/kernel/gen_kheaders.sh
index aff79e461fc9..8aa6d3c37ba7 100755
--- a/kernel/gen_kheaders.sh
+++ b/kernel/gen_kheaders.sh
@@ -41,10 +41,10 @@ obj_files_md5="$(find $dir_list -name "*.h"			   |
 this_file_md5="$(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
 
-- 
2.17.1