Basic UNIX and bash commands

CAPITAL LETTERS describe a required argument.

[square brackets] indicate optional parameters, flags, or options.

The basic command syntax looks like this:

command --option PARAMETER

GNU coreutils and shell commands

• echo [string] outputs the string.
• ls [-alh] [dir] displays the contents of the directory DIR.
  • ls -a lists all files, including . and .., as well as hidden files (which filenames begin with .).
  • ls -l lists files with metadata, such as permissions, owner, size, and date.
    • ls -lh reports the information in "human readable" format.
• cd DIR changes the current working directory to DIR.
• mkdir DIR creates a new directory.
• rmdir DIR deletes an empty directory.
• rm FILE deletes a file. (accepts multiple arguments)
• touch FILE creates a blank file called FILE.
• cat concatenates the input stream and prints to the output stream.
  • cat FILE prints the content of FILE
  • cat > FILE will write the standard input stream out to FILE. End this command by pressing CTRL-D.
• man COMMAND shows the manual page for COMMAND.
• whatis COMMAND shows a brief, one-line description of COMMAND.
• sudo COMMAND runs COMMAND with superuser (root) privileges.
• grep REGEX [file] filters the input stream or file based on a regular expression.
  • fgrep or grep -F forces literal evaluation of string.
  • I strongly recommend you add alias grep='grep --color' to your ~/.bashrc file.

System administration

• nano [file] opens an easy-to-use text-based text editor.
• vim [file] opens an advanced text-based text editor.
• ln -s TARGET LINKNAME creates a symbolic link.
• sudo -s enters $SHELL as the root user.
• sudoedit FILE edits a file as the root user. ($SUDO_EDITOR must be set, recommend rvim)
• dmesg [-H] print the kernel ring buffer (debug messages produced by the kernel)
• journalctl -b [-r] shows systemd log entries from the current boot.