Logging in omega

If you are on campus, you can login to omega.uta.edu from any computer on UTA wifi. If you are off campus, you must use Pulse Secure VPN first.


• Windows 10 users:
  • Enter ssh abc1234@omega.uta.edu in the search box where abc1234 is to be replaced by your NetID.
    
    
    
• Mac users: Terminal app -> omega.uta.edu

Getting around Unix

• Issue the following commands ($ is the system prompt, do not type it) exactly as shown:

  $ cp ~sn/.bash_profile . $ source .bash_profile

  This enables control-Z in nano (by default it is disabled). Required once and for all.
• Play with the following commands and figure out what they do.
  • ls (directory listing)
  • ls -l (directory listing in long format)
  • ls -lt | more (one screen at one time, long format, chronological order)
  • dir (same as ls)
  • whoami
  • who
  • cal (calendar)
  • cal 1980
  • up/down arrow (control-P, control-N) (recalling previous commands)
  • (bring up who) and control-A, control-E, control-F, control-B, control-D
  • ls . (current directory)
  • cd .. (directory one level up)
  • pwd (present working directory)
  • cd / (goes to the top directory)
  • cd (return to your home directory)
  • mkdir MyNewFolder (create a new directory)
  • rmdir MyN(tab) (remove a directory)
  • nano junk.txt (create a new file)
  • cp junk.txt junk2.txt (copy)
  • mv junk.txt junknew.txt (rename)
  • rm junk.txt (delete)
  • rm *.c (do not do this)

nano/your first C program

• $ nano MyFirstProgram.c
• enter the following:

  #include <stdio.h> int main() { printf("Hello world !\n"); return 0; }
• Up/down arrow, control-A, control-E, control-F, control-B, control-D, control-K.
• Try control-K and control-U (uncut)
• To save the document, control-o
• To exit from nano temporarily, control-Z.
• fg to get back to nano.
• control-Z again, try

  $ ls $ ls -lga MyFirstProgram.c $ cat MyFirstProgram.c
• At the prompt, type

  $ gcc MyFirstProgram.c $ a.out
• if a.out does not work, try ./a.out.
• fg to get back to nano, edit and run again.
• to exit from nano, control-x.
• to exit from omega.uta.edu, control-D or type logoff or exit.

1. Prints three blank lines followed by "Hello World."
   Sample program:

   #include <stdio.h> int main() { /* this is a comment */ printf("Hello UTA !"); printf("\nHello World !\n"); return 0; }

   \ n sends a new line.
2. Reads two real numbers from the keyboard and prints their product.
   Sample program:

   #include <stdio.h> int main() { int a, b; /* to declare that a and b are integer variables */ printf("Enter two integer numbers separated by space ="); scanf("%d %d", &a, &b); /* this is the way to read two integer numbers and assigned them to a and b */ printf("The sum of the two numbers is %d.\n", a+b); /* %d is for integer format*/ return 0; }

   • Use int for integers, float for floating (real) numbers.
   • To enter the value of a variable from the keyboard (standard input), use scanf().
   • The scanf function reads input from the keyboard in the format specified by (%d %d) and assigns each value to the variable followed.
   • Use %d for integer and %f for float.
   • Add an ampersand (&) before each variable when using the scanf function for a reason too early to discuss.
   • The printf function prints a string to the screen (standard output). When it encounters a format (such as %d), it replaces that part by the variable followed.
3. Reads a real number and outputs its inverse. If 0 is read, writes a warning message and quit.
   Sample program:

   #include <stdio.h> int main() { float a; printf("Enter a number = ");scanf("%f", &a); if (a==0.0) printf("You entered 0.\n"); else printf("You entered a number other than 0.\n"); return 0; }
4. Reads a real number, x, and outputs its sine, i.e. sin x. You need to use math.h and the -lm compile option.
   Sample program:

   #include <stdio.h> #include <math.h> int main() { float x; printf("Enter a number ="); scanf("%f", &x); printf("x= %f exp(x)=%f\n",x, exp(x)); return 0; }

   Sample run (note the -lm option):

   $ gcc -lm myprogram.c $ a.out