Seven Basic Commands

• 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.

Getting help from man pages

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).

Help Systems Overview

• 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

Globbing (Wildcards)

• * => 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.

Find Command

Archiving Files with Tar

• 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)

Example 0: Checking File type

• 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

Example 1: Archiving Files:

• In the first example, archiving files in the current working directory.

• In the second example, looking into the tar archive without extracting it.

Example 2: Extracting files in a different directory:

Example 3: Compressing files with -z (gzip tool)

tar -czvf the_file_name.tgz archive.tar

Understanding Compression Utilities

• 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)