Useful Commands I

Below, you can find some useful commands including examples.

$ more         → Display a text file „page by page“. Often replaced by less nowadays.

$ less         → Display a text file.

$ cat           → Display the content of a file.  

$ du             → Show the space occupied by directories and files.
$ du -sh . → Space used in the current directory.

$ file filename → Identify the type of the file filename. The idenfication is based on so called „magic numbers“, this means that file extensions are meaningless!

$ touch → Change the time stamp of a file. It can also be used to create an (empty) file.

$ touch file.txt
$ ls -lh
  -rw-r--r-- 1 user1 users   0 16. Nov 15:30 file.txt

$ mkdir → make directories. Create one or more directories or subdirectories.

$ mkdir dirname
$ mkdir dir1/dir2 → create the directory dir2 below dir1.

$ diff → Display the differences between two files or directories.

$ diff file1 file2
$ diff dir1 dir2

$ cp       → copy. Copy files.
$ cp -r → Copy directories.

$ cp file1 file2
$ cp file1 dir1/file1
$ cp file1 dir1/file2 → What is the difference?

$ cp -r dir1 dir2/dir3

$ mv → move. Move or rename files or directories.

$ mv dir1 dir2/ → move dir1 to direcory dir2.

$ mv dir1 dir2/dir3 → move and rename.
$ mv file1 file2       → remame.

$ rm       → Delete file.
$ rm -r → Delete directories.

$ rm -rf → This also deletes directories. What is the difference?

$ rmdir → Alternative command to remove directories.

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