create large file with dd command

要一個大的 file 作 loop back。
要先 create。

以往都是用： dd if=/dev/zero of=10G bs=1G count=10 這樣會花一些時間，硬碟把 00 寫入 10G 的 file。


要是不管file 的內容，只要10G 大小，可以用： dd if=/dev/zero of=10G bs=1 count=0 seek=10G 這樣馬上就可以create 出來。

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• http://www.skorks.com/2010/03/how-to-quickly-generate-a-large-file-on-the-command-line-with-linux/

copy files according the list file

其實這是 moore 的 script。
他把各系統要 copy 的 filename 寫在同一個 list file 中，每個 filename 用 ≶ > 刮起來。
仿造 xml 格式，裡面是 系統名稱。
<N_Series>MyBrowser.apk</N_Series>

所以要寫一個 script，依照這個 list 內容來 copy files..

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要注意那個從 filelist xml 中剔除 tag 的 sed，要先把 </...> 剔除，再剔除開頭的。
否則因為整個 entry 剛好被包圍，所以會被整個剔除。

test condition : file, directory

用在 if, while 等 流程控制 的判斷，像
if [ -f /etc/passwd ]; then
echo "found"
else
echo "not found"
fi
其中的 -f 就代表 is a file.

在 https://sites.google.com/site/tiger2000/home 有列出所有的 file test 選項：
[ -e file ] file exists
[ -f file ] file is a file
[ -d file ] file is a directory
[ -c file ] file is a character device
[ -b file ] file is a block device
[ -p file ] file is a named pipe
[ -s file ] file is not empty
[ -k file ] file's sticky bit is set
[ -S file ] file is a socket
[ -L file ] file is a symbolic link
[ -r file ] file is readable by user
[ -w file ] file is writeable by user
[ -x file ] file is executeable by user
[ -O file ] file is owner by user
[ -G file ] file is group owned by a greoup
[ -u file ] file has its set user ID bit set
[ -g file ] file has its group user ID bit set
[ file1 -nt file2 ] file1 is newer than file2
[ file1 -ot file2 ] file1 is older than file2
[ file -ef file2 ] file1 is another name for file2
[ $str1 = $str2 ] str1 string is the same as string str2

另外一個，是 and , or 的 邏輯運算:

-a and
-o or
! not
* 奇怪的是 這些 邏輯運算後面的 operand 好像要加"" 括號