Shulou(Shulou.com)06/03 Report--

What are the commands for manipulating file directories in CentOS? In this paper, five commands about file directory are given, and the simple usage of the demonstration is demonstrated. Zero basis can also refer to this article, and interested friends can refer to it.

1. Cp (copy files or directories)

In addition to simple copying, cp can also create linked files that can be updated compared to the old and new of the two files.

Cp (copy a file or directory)

Cp [- adfilprsu] Source file (source) object file (destination)

Cp [options] source1 source2 source3.... Directory

Options and parameters:

-a: equivalent to-dr-- preserve=all, (commonly used)

-d: if the source file is an attribute of the linked file (link file), copy the linked file attribute instead of the file itself

-f: for force, if the target file already exists and cannot be opened, remove it and try again

-I: if the target file (destination) already exists, the action will be asked first when overwriting (commonly used)

-l: create a hard link linked file instead of copying the file itself

-p: copy it along with the file's attributes (permissions, user, time) instead of using the default attributes (commonly used for backup)

-r: recursive continuous replication, used for directory replication behavior; (commonly used)

-s: copy as a symbolic link file (symbolic link), that is, a "shortcut" file

-u: destination updates destination only when it is older than source, or replicates only if destination does not exist.

-- preserve=all: in addition to the permission-related parameters of-p, the attributes of SELinux are also added, and links, xattr and other attributes are also copied.

Note: if there are more than two source files, the last destination file must be a "directory".

Copy (cp) this instruction is very important, different identities of the implementation of this instruction will have different results, especially the option of-a,-p, for different identities, the difference is very large, this is mainly because only root users have permission to modify the owner of files and directories, when some ordinary users-a-p parameter may not be effective.

1. Test 1: the following test first logs in to the system as a fromheart user, establishes a file test under its home directory, and then switches to the root user without a parameter-p to view the attribute difference between the copied file and the source file.

Touch test

Su-

Pwd

Cp / home/fromheart/test.

Cp / home/fromheart/test testp

Ls-al / home/fromheart/test test testp

From the following figure, it can be found that when the parameter-p is taken, the system maintains the original relevant attributes of the file (owner, permissions of relevant users or groups).

Generally speaking, if we go to copy other people's data (of course, the file user must have the permission of read), we always want to copy the data to our own, so, in the default condition, the permission of the source file of cp is different from that of the target file, and the owner of the target file is usually the instruction operator himself.

2. Test 2: in the following test, first create directories 1, 2 and 3 under the fromheart home directory of the currently logged-in user, respectively, and then copy the directory 1 (including subdirectory 2 under the directory) to directory 3 through the cp-r command:

Mkdir-p 1max 2

Mkdir 3

Cp 1 3 (error prompt)

Cp-r 1 3

Ls-alR 1 3

Note:-r you can copy directories, but the permissions of files and directories may be changed. This should be particularly noted when backing up, as users are likely to need to maintain the properties of the source file during the backup. In the figure above, the permissions remain unchanged because the users operate in their home directory.

Test 3: create a link file (symbolic link)

Using-l and-s will create so-called linked files (link file), but these two kinds of linked files have different situations, in which-l is the so-called hard link (hard link), while-s is a soft link (symbolic link), which is equivalent to a shortcut under windows.

To put it simply, a soft link is a "shortcut" that links to the source file! So the user will see a symbol pointing to (- >) to the right of the file name.

The properties of the hard link target file and the source file are exactly the same as the permissions, and the difference before the link is that the number of link in the second column of its properties has changed from 1 to 2. At the same time, when the content of the source file changes, the hard link target file will also change.

Mkdir sl ll (create two directories, sl to store soft-linked source files, sl.txt,ll to store hard-linked source files ll.txt)

Touch sl/sl.txt ll/ll.txt (create two empty files sl.txt ll.txt in each of the above two files)

Cp-s sl/sl.txt sl.txts (generate a soft-link file sl.txts through the cp-s command)

Cp-l ll/ll.txt ll.txtl (generate a hard-linked file ll.txtl through the cp-l command)

Ls-ali ll/ll.txt ll.txtl (check the inode and other details of the hard-linked source file and target file, and find that the inode of the two files is the same, and the number of file connections has become 2. Note that for hard-linked source files that exist in different directories, users can use the find /-inode command to find them.)

Ls-ali sl/sl.txt sl.txts (soft link source target file is exactly the same)

Test 3: copy the source file when it is newer than the target file

Format: cp-u source file name destination file name (commonly used for backup operations)

Test 4: copy the actual file of the linked file (not a linked file, that is, a shortcut)

Format: cp-d source file name destination file name

As shown.

Example 5: copy multiple files to a directory at a time

Format: cp [options] source1 source2 source3. Directory

You can copy multiple data to the same directory at once! There must be a catalog at the end!

In short, because cp has a variety of file attributes and permissions, so, before the copy operation, users must clearly understand: do you need to retain the source file information? Is the source file a linked file (symbolic link file)? Is the source file special, such as FIFO, socket, etc.? Is the source file a directory? Is it from multiple files?

2. Rm (remove files or directories)

Format |: rm [- fir] file or directory

Options and parameters:

-f: it means force. Ignore files that do not exist and there will be no warning messages.

-I: interactive mode, which asks the user whether to act before deleting it.

-r: delete it recursively! But delete the directory and everything under the directory, which is a very dangerous option.

Touch file1 file2

Mkdir-p 1-2-3

Ls

Rm file1 file2

Rm 1 (hint 1 is a directory and cannot be deleted)

Rm-p 1 (delete directory 1 and all file directories under directory 1)

Rm also supports wildcard operations, rm fil*

Note: when deleting a file that begins with -, such as rm-aaaa, the system will indicate that the deletion is not successful, because the system will use the file name starting with-as the operation option of the command, so it cannot be deleted successfully.

At this time, users can use the following two ways to avoid the first character is "-" method: one is to add ". /" in front of the file directory name, rm. /-aaaa; is rm-aaa-- is also possible.

Touch. /-aaa. /-aaaa

Ls

Rm-aaa

Rm-aaaa

Rm. /-aaa

Rm-aaaa

Ls

3. Mv (move files and directories, or rename)

Format: mv [- fiu] source destination

Format: mv [options] source1 source2 source3. Directory

Options and parameters:

-f: force force means that if the target file already exists, it will be overwritten without being asked.

-I: if the target file (destination) already exists, it will be asked whether to overwrite it!

-u: if the target file already exists and the source is relatively new, it will be updated (update)

If there are multiple source files or directories, the last target file must be a "directory", which means that all data is moved to that directory.

Users can also change their names through rename and view related operations through man rename.

4. The name of the file to get the path basename

5. Get the directory name of the path dirname

The full file name of each file contains the previous directory and the final file name, and the length of each file name can reach 255 characters! So how does the user know that's the file name? Is that the name of the directory? Of course, it is to use the slash (/) to distinguish! In fact, the general purpose of obtaining a file name or directory name should be used to judge when writing a program.

Basename / etc/sysconfig/network

Network (get the last file name)

Dirname / etc/sysconfig/network

/ etc/sysconfig (the acquired directory name)

This is the end of the command on operating the file directory in CentOS. I hope the above content can be of some help to you and learn more knowledge. If you think the article is good, you can share it for more people to see.

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