LAB2 PROCESS CONTROL 

PROCESS MANAGEMENT

    When working in a shell environment, multiple jobs can be started. Each program executed is a job. if you run Netscape then Netscape is a job. Every job whether user invoked or by the system has an associated job number and an id. The jobs the user invokes have a user id or UID. Jobs that are run by the system have root UID. Follow the instruction below to understand how to manage your jobs. There will come a time when you will want to terminate a job and it will be necessary to understand how to do it without any problems.

1. The top command
   
• type top at the command prompt
• keep pressing enter to refresh the window. 
• locate the PID column
• locate the SIZE column
• locate the COMMAND column
• locate the USER column

• press the Ctrl C key to get out of top
• type matlab <enter>
• go to another shell and invoke top
• locate matlab on the right column and its corresponding PID number
• copy or remember the number and get out of top ( Press the Ctrl key and the letter "C" key at the same time....)
• type kill followed by the PID number e.g. kill 10188 <enter>
• $ kill 10188
  
• matlab should have been killed
1. ps command
• type ps 
• the ps command alone will show you what shell you are running i.e. bash shell
• type tcsh 
• Now you have switched over to Tomcshell. This type of shell is really popular in dec-alpha and sgi machines. Linux prefers the bash shell because it is more powerful. In this course we will be confining ourselves to the bash shell
• to get out the tcsh shell 
• type exit
• You should be back in the bash shell environment. To check, type ps again
• Now do the following in the shell
• ps -ef
• ps -ej
• this is another way of checking your jobs or system jobs

1. Background(bg) and Foreground(fg) jobs

• type the following commands
• nedit &
• you have just created a background job for the nedit editor. The command prompt re-appears and is good to go !
  
• jobs
• jobs will list the programs running specific to this shell. Its like a local variable i.e. other shells will not know about it. The job number is the number within the square brackets e.g. [1]
• kill %job number
• e.g. kill %1
  
• nedit &
• fg
• the job moves to the foreground and uses the shell
• Ctrl ^c (press the Ctrl key and the leter c key at the same time. The ^ symbol is a control sequence specifier)
• this will kill the job
• Now type
  
• nedit
• Ctrl ^z
• bg
  
• this will put the job in the background
1. Mounting a floppy or cd (optional)
• The floppy
• insert the floppy into the bay
• type mount /mnt/floppy <enter>
• type cp /mnt/floppy/* .
• The above command copies all the files in the floppy into the dir from where you have issued the command.
• *  is a wild card symbol it tells the shell that verything is game for copy. ~/ is your home dir ..... remember ??
• . the period tells the shell that you want to copy the contents of floppy from some dir into that dir !
• go into floppy byh typing cd /mnt/floppy
• type ls to view the contenst fo the floppy
• type cp or mv * ~/aeror361/lab2
• The cdrom
• insert the cd
• type mount /mnt/cdrom
• copy and move like you have been doing. You can write into this cd since its a read write cdrw
2. Standard Input and Standard output

• There may be times when you copy the contenst of a man page to a file. The output to the terminal from the density program may also be needed to be copied to a file or you may want to read in your altithude from a file without open statement in your code. For such occasions we use the standard output symbol ">" and the standard input symbol "<" .

• type the following commands
• type man ls > man.dat
• type ls 
• there should be a file man.dat in that dir

• type cat man.dat 
• this will show you the contents of the file non stop
• type less man.dat
• this will show you the contents of the file with user having control over the scroll speed
• use the up and down arrows and the enter key to scroll
• the same with more, but with a minor difference. I leave that to you.
• in the exe/ dir of your density code create a file called input.dat
  
• insert your altitude in input.dat and save-exit the file
  
• type ./code.x < input.dat 
• the code should run the same way as before

1. copy a dir and its contents

• cp -r aero361 aero361_dummy
• -r option is the recursive flag that tells the command to copy the dir and everything in it
• man cp 
• check out other neat options, specially the -i option

1. rm a dir and its contents
• rm -rf aero361_dummy
• the -rf option removes recursively and overides the -i option 
• man rm
• check out other neat options
  

Using the man page : Problem Statement (20 pts) (USE gnumeric SPREAD SHEET)

A table prepared using "xess" in the following form:
 

Command	Options	Description
ls		list the contents of a directory
	a	list all files ( includes  .files )
	d	.
	F	.
	l	.

SYMBOLS LEARNT THUS FAR

These symbols have more than one meaning, but in the context of todays lab they represent the following

• ~
• home dir path
  
• *
• wild card that selects all strings
  
• > and <
• standard input and standard output
• &
• bg job 
• .
• current dir short cut
• @
• host name
• ^
• control key 
• %
• job number