whoami
- showing the name of the current user
hostname
- showing the name of the host
uname -a
- information about the kernel, build and platform
passwd
- manage password
touch
- create a new file and change the timestamp
date
- shows the current date and time and you can also set the current date and time.
last
- all the users that have logged into your system last.
Command summary: shows how to use command
Items between [brackets]
are optional
If you see { a | b }
, you must choose one of them
And, ...
means you may have more of the preceding items
Man pages have sections
1 is for end-user commands
5 is for configuration files
8 is for administrator (root) commands
Many man pages have examples towards the end. Otherwise, they will have related items sometimes.
User /searchtext
to search for text inside the man page
Use q
to get out of the man page
Press small g
to go top in the man page and press capital G
to go down.
For example:
[OPTIONS]
- Though optional because it is inside the square brackets, you can replace them by the options such as --help
, --version
...
shows you can give more than one option at a time(, it didn't work though in this case).
man is the primary source
command --help provides short usage overview
/user/share/doc contains additional help from some commands
pinfo shows usage information for some commands
*
=> for everything
?
=> for one single character
[a-z]
=> for range
Remember, they can be combined together
Examples:
ls -d a*
=> all directories with the name a.
ls *a
=> all files that ends with a.
ls -d a?s*
=> directories that starts with a, then any single character, then s and then any number of any characters
ls -d [a-z]?
=> directories whose first character would be between a and z and the second character would be anything.
Tar is Tape ARchiver and was created a long time ago.
Basic use is to compress, extract, or list
tar -cvf my_archive.tar /home
Creates tar archive of home directory.
tar -xvf my_archive
Notice this extracts to the current directory
Use -C
to switch the output path
tar -tvf my_archive.tar
will show the contents of an archive without extracting it.
Add compression using -z
(gzip) or -j
(bzip)
file
utility helps us identify the file type without touching it.
Linux doesn't have a special usage of a file extension but it does
In the first example, archiving files in the current working directory.
In the second example, looking into the tar archive without extracting it.
tar -czvf the_file_name.tgz archive.tar
gzip -(z) is the most common compression utility
bzip2 (-j) is an alternative utility
zip can be used as well, and has a Windows-compatible syntax.
Some other compression utilities exit as well. (xz)