Perl learning notes 13 objective operations

1. Change the Directory

Chdir "/etc" or die "can't chdir to '/etc '! \ N ";

If the parameter is omitted, the system returns to the user's home directory, which is the same as that of CD;

2. wildcard file name

My @ all_files = glob "*"; # files starting with a dot are not included.

My @ pm_files = glob "*. PM ";

Multiple matching modes are separated by spaces: My @ files = ". **"; # All files can be matched, including

3. Fill in another syntax for file names

My @ files = <* >;## is equivalent to: My @ files = glob "*";

Supports variable interpolation: My $ dir = "/etc"; my @ dir_files = <$ DIR/* $ DIR/. *>;

Angle brackets support configuration of file handles and file names. Perl will determine which operation to choose. If it is an identifier, it will be read as a file; otherwise, it will be processed according to the file name Configuration:

4. Directory handle

Directory handle can be opened (opendir), read (readdir, read as file name), close (close );

A directory handle is a low-level operator that only Returns basic information and requires additional processing.

5. delete an object

Unlink "file1", "file2", "file3"; # The number of successfully deleted files returned.

Cannot be used to delete directories;

Delete multiple files at a time: unlink glob "*. O ";

The permission to delete a file is independent of the permission of the file itself, and depends on the permission of the directory where the file is located. Therefore, a file that cannot be read, written, or executed may also be deleted;

6. Rename an object

Rename "old", "new ";

Achieve effects similar to MV: Rename "/home/place/file1" "file2"

7. Links and files

Hard link:

This will increase the number of links to a file. As long as one link exists, the file exists.

You cannot increase the number of links to a directory or link to a volume.

Soft link (symbolic link ):

It does not increase the number of links to files and can point to non-existing files.

Position to which the symbolic link points:

8. Create and remove Directories

Create a directory:

 

0755 is the permission, and strings cannot be directly interpreted as Octal numbers. The OTC function is required:

Remove directory:

Only one directory can be deleted at a time, and it must be an empty directory. If it is not an empty directory, you can use unlink to delete it:

$: Current process number.

If there are subdirectories in the directory, unlink will fail, resulting in rmdir failure. File: rmtree in the path module provides a complete solution.

9. Modify permissions

Chmod 0755, "file1", "file2 ";

10. Change the Affiliation

User identifiers and group identifiers must be specified in the form of digits. If you do not know, you can use the following method:

11. Modify the timestamp

The third timestamp ctime must be set to now. No function can modify it.