Thalasar Ventures

Essential Tools
A Linux shell environment also takes commands that tell users information about what their system is doing at any given time. Typing “who” and pressing “enter” displays the login names of any other users that may be logged into the system if a networked computer is being used. Any UNIX/Linux system is capable of a great deal of multi-tasking, often more efficiently than other types of operating systems.

Processes can be run in the background while the user is working on other tasks, and all of these can be tracked through use of the command line. Typing “ps” (for processes) lists every process that is currently running on the system. The resulting list also links each process to each user that is running it. The UN D^Linux system also assigns a unique identification number to each process, which is one of the foundations of modern database administration.

Basic commands such as “ps” and “who” get increasingly specific as the user needs to list more detailed information. More specific instructions are tagged onto these types of commands with a minus sign, and these instructions are referred to as arguments, which ties into programming logic. The basic utilities that are entered into the shell with a minus sign and argument are interpreted as options to be executed, provided the arguments have been entered correctly. An important UNIX/Linux concept to remember is that any words or abbreviations on the command line that are not interpreted as utilities are automatically interpreted as arguments.

Combinations of Commands
Once the user feels comfortable entering a utility followed by a single argument, it is time to bring data together using command combinations that get a little more complex Multiple files can be created with a utility called the “cat” utility. An example would be entering “cat filei file2” The “cat utility interprets each of these arguments as a separate file to be created and saved. The results are two new files that are concatenated, or spliced together because no redirection instructions have been specified.

Another very commonly-used Linux character is the output redirection symbol, which is the > symbol on the keyboard. This symbol tells the Linux shell to redirect the output of any given utility to a certain file; an example would look like this: cat file3 >folden. The file named folden contains the contents of file3. This can be done with any given number of files entered to the left of the output redirection symbol.

When working with large files that contain many lines of content, it is useful to have a command that will locate a specific string of text quickly without the user having to search manually for it. The “grep” utility serves this purpose. This command is entered as such: grep have folden. Any lines containing the word “have” in the file named folden will be displayed. This combination of commands follows the basic premise of a search engine for any user-created files.