Review the contents of the previous section:
1. Scheduled execution of Task commands Crontab–e, crontab–l,crontab–r
2. Job: Define a timed task to output Hello World to the/tmp/test.txt file every minute
Crontab–e
*/1 * * * * echo ' Hello World ' >>/tmp/test.txt
In this section, let's take a look at file and directory management
1. Computer operating system using directory organization files
2. All file systems form a directory tree structure
3. The directory tree has a root directory
4. View current directory command: PWD
5. Relative path and absolute path
The path to find starting from the root path is an absolute path, such as/usr/bin
The path relative to the current path, such as the current USR path, is the relative path, because the bin path is not started from the root path, but instead is looked up in USR as a relative path.
6. ... and.. The use
In each directory there will be two special directories, respectively. and.
A point. Represents the current directory, two points: Represents the previous level directory of the current directory
Job: Enter the OPT path, using the relative path method and the absolute path method to enter into the actually any sub-directory
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Linux System Command Learning Series-File and directory management