First, the file management commands
1, cp command, copy
a, single source replication, cp [OPTION] ... [-T] SOURCE DEST
If DEST does not exist: the pre-create this file, and copy the data flow to the source file in the DEST.
If there is DEST:
If the DEST non-directory file overwrite the destination file, if the file is a directory DEST create a file with the same name as the source file in the DEST directory, and copy its data stream to the target file.
b, multi-source copy
cp [OPTION]... SOURCE... DIRECTORY
cp [OPTION]... -t DIRECTORY SOURCE...
If there is no DEST: Error
If there is DEST:
If a non-directory file DEST: Error
If the file is a directory DEST: each copy each file to the target directory, and keep the original name
c, cp -i: interactive copy, that is to remind the user for confirmation before coverage
d, cp -f: mandatory coverage target file
e, cp -r: recursive copy directories
[root@localhost /]# cp -r /var/log/ /tmp/ [root@localhost /]# ls /tmp/ a_c a_d b_c b_d functions hi.txt log vmware-root x
f, cp -d: If you copy a symbolic link soft link like this shortcut, the default will he source data file will be copied, if we do not want to copy the data source file only symbolic links you will need to copy plus -d option.
g, cp -a: not only copy the source file data source file also retains all metadata attributes. By default, this parameter is added cp -dr --preserv = all parameter. --preserv options are as follows
--preserv=
mode: Permissions
ownership: the owner and group
timestamps: timestamps
context: security label
xattr: Extended Attributes
links: symbolic link
all: All of the above properties
2, mv command: move
mv [OPTION]... [-T] SOURCE DEST
mv [OPTION]... SOURCE... DIRECTORY
mv [OPTION]... -t DIRECTORY SOURCE...
a, mv -i: Interactive Copy
b、mv -f ：force
3, rm command: remove
a、rm -i ：interactive
b、rm -f：force
c、rm -r：recursive
d, Delete directories: rm -rf / PATH / TO / DIR
e, note: all the different files is not recommended deleted, but moved to a special directory :( simulation Recycle Bin)
Second, variable
1, named memory space
Variable types: integer, floating point, character, Boolean, date and time type
Character:
Numeric:
Exact numeric:
Approximate values:
Variable type determines the storage format, the range of data involved in computing