Executing Commands

The Command PATH:

  • Most common commands are located in your shell’s “PATH”, meaning that you can just
    type the name of the program to execute it.

    Example: Typing “ ls” will execute the “ ls” command.
  • Your shell’s “PATH” variable includes the most common program locations, such as
    /bin, /usr/bin, /usr/X11R6/bin, and others.
  • To execute commands that are not in your current PATH, you have to give the complete
    location of the command.

    Examples: /home/bob/myprogram
    ./program (Execute a program in the current directory)
    ~/bin/program (Execute program from a personal bin directory)


Command Syntax

  • Commands can be run by themselves, or you can pass in additional arguments to make them do
    different things. Typical command syntax can look something like this:

    command [-argument] [-argument] [--argument] [file]
    ls List files in current directory
    ls -l Lists files in “long” format
    ls -l --color As above, with colourized output
    cat filename Show contents of a file
    cat -n filename Show contents of a file, with line numbers