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Linux General Commands
This is a more generalized listing of different commands used in navigating and manipulating linux environments and programs.
These commands are good to keep in mind when doing any sort of work on a UNIX computer.
- man command : Gives information from the UNIX manual about command.
Also, man -k word will list manual pages whose titles contain the keyword word.
- Ctrl+C : Usually kills whatever you are doing and signals the shell to accept the next command. Use Ctrl+C only if you are stuck, since work you did during the killed command may be lost.
- Ctrl+Z : This control code temporarily suspends a command, whereupon the shell can accept the next command. Use the fg (foreground) command to get the suspended process running again; type jobs to see if you have any suspended or background processes.
- crypt input output : Encrypt or decrypt a file (it knows which way to go). It will ask you for a key. The algorithm is not sufficiently strong for national security issues.
- date :Displays the current date and time.
- finger name : Looks up the loginID of name. e.g. finger Gilfong will give you the loginID (and full name) of everyone named Gilfong. Be prepared for a lot of output with common names. You can also specify the loginID to find the person's full name.
- gunzip file :The inverse of gzip: restores the original file.
- gzip file : Compresses file. The full-size file is removed and the compressed file has the same name with an extension of ".gz" added. You can get 4 to 1 compression on low-entropy data.
- hostname : Gives the name of the computer on which you are currently working.
- kill pid : Cancel the process with identification pid
- pkill process : Cancel the named process - e.g. pkill mybustedscript
- less : Displays text files one page at a time. Press "h" for help, "q" to quit", SPACE to go to the next page, "b" for previous page, "/" to search, etc.
- logout : Ends your session. If you ran multiple shells you may need to run this for each nested process.
- locate file : gives the location of file based on the contents of a database which is updated nightly
- nice -prior program : Gives program processing priority value prior (1 being the highest priority level and 19 the lowest) which tells the computer how to process tasks.
e.g. nice -19 ./a.out & runs the program a.out in the background at the lowest priority.
- passwd : Changes your password. You will be asked to type the old password first, and then the new password twice. None of this is visible on the screen.
- command1 | command2 : Called the “pipe” command. Takes the output of command command1 and uses it as the input for command2.
e.g. ls | less lists files in the current directory and views the results in a paginated form
- uptime : Shows the load on the computer you are currently using.
- who : Lists all users on the computer in which you are currently working.
- whoami : Tells who is currently logged on a specific terminal