What is the use of linux cp command?

In Linux, the cp command is used to copy files or directories. One or more source files or directories can be copied to a specified destination file or directory. The syntax is "cp [option] source file target file". The cp command supports copying multiple files at the same time. When copying multiple files at one time, the target file parameter must be an existing directory, otherwise an error will occur.

#The operating environment of this tutorial: linux7.3 system, Dell G3 computer.

Linux cp command

The cp command is mainly used to copy files or directories. That is, it is used to copy one or more source files or directories to the specified destination file or directory.

The cp command can copy a single source file into a specific file with a specified file name or an existing directory.

The cp command supports copying multiple files at the same time. When copying multiple files at one time, the target file parameter must be an existing directory, otherwise an error will occur.

cp command syntax

cp [-options] source_file dest_file

• source_file: source file, specify the source file list. The cp command cannot copy directories by default unless the -r/-R option is used.

• dest_file: Destination file, specify the destination file. When the "source file" is multiple files, the "target file" is required to be the specified directory.

Parameter description:

• -a: equal to "dpR" parameter combination, usually retaining links and file attributes when copying directories , and copies everything in the directory.
• -b: Back up the target file before overwriting the existing file target;
• -d: Keep the symbolic link when copying.
• -f: Forcibly copy files or directories, overwriting existing target files without giving a prompt.
• -i: Contrary to the -f option, a prompt is given before overwriting the target file, asking the user to confirm whether to overwrite.
• -l: Does not copy the file, just generates a hard link file of the source file.
• -p: Preserve the attributes of the source file or directory when copying the file.
• -r: Copy the directory recursively, that is, copy the directory and all its subdirectories and files.
• -R: Same as -r option parameter.
• -s: Establish a symbolic link to the source file instead of copying the file;
• -S: When backing up the file, use the specified suffix "SUFFIX" instead of the default suffix of the file;
• -u: Copy the source file synchronously, only when the source file is updated or the target file does not exist.
• -v: Display the operations performed by the command in detail.

Examples of using the cp command

The cp command is used in Linux to copy files (folders). This article summarizes the cp commands commonly used in daily work as follows.

1. Copy a source file to the target file (folder)

The command format is:cp source file target File (folder)

This is the most frequently used command, responsible for copying a source file to the target file (folder). As shown in the figure below, when copied to a folder, the file name remains unchanged; when copied to a file, the file name changes. If the target file already exists or the target folder contains a file with the same name, the target file or the file with the same name in the target folder will be overwritten after copying.

2. Copy multiple files to the target file (folder) at the same time

The command format is:cp source file 1 source file 2 target folder or cp file* target folder

This command Frequency of use is also high. The first command format can copy multiple listed files to the target folder at once, with each file directly separated by spaces; the second command format uses the wildcard *, as shown in the figure below, to copy all files starting with " .txt" are copied to the folder testDir.

3. Copy the source folder to the target folder

The command format is:cp -r source folder target file Folder

This is also a frequently used command. Just remember to add the "-r" parameter when copying a folder, otherwise the "cp: omitting directory" error will occur.

##4. Copy only when the source file is newer than the target file

The command format is:cp -u source file target file

This command is very practical, especially when updating files. As shown in the figure below, the source file will be copied to the target file only if the source file is newer than the target file. Otherwise, even if the command is executed in time, the copy will not be performed.

5. Create a soft link to the file

The command format is:cp -s source file target file

You can also use the ln command to achieve the same function. When a file path is too deep (such as a/b/c/d/e/orginalFile.txt below) and it is very inconvenient to access, a soft link to the file will be created to make it more convenient to access. Soft links are equivalent to shortcuts on Windows.

6. Create a hard link to the file

The command format is:cp -l source file target file

You can also use the ln command to achieve the same function. Sometimes, for some reason, you need to create a hard link, as shown in the image below.

Here is a brief introduction to the difference between hard links and soft links. As shown in the figure below, the soft link file (softLink.txt) and the linked file (orginalFile.txt) have different inodes (133827 and 139819), and the hard link file (hardLink.txt) and the linked file (orginalFile22. txt) has the same inode (156981). When the linked file is deleted, the soft link file cannot be accessed, but the hard link file can still be accessed normally.

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