CS3423 Pgm#8 Process Control (40 pts) This assignment involves creating a parallel shell tool called PELL. It provides users of pell with the ability to execute commands, execute multistep processes connected by pipes, and execute concurrent independent processes.

PELL supports the following major commands: conc cmd1 args1 , cmd2 args2 , ...

conc causes PELL to execute the commands concurrently (i.e., in parallel). There is no communication between the commands, these simply happen in parallel. fork each of the children. The maximum number of commands is 5. If any of the commands redirect input or output, you must do the redirection after forking, but before execing. The getCommands function has been provided to simplify the process of getting the command arguments and redirection values. Example: conc ls l /bin > lsOne.txt , ls l /usr/bin > lsTwo.txt , ls l /etc > lsThree.txt Each of the ls commands are executing in parallel. The conc command prints each of the parallel commands showing the parent's process Id, child's process ID, the command, and command arguments. Your actual PID values will be different. 33009 33011: ls l /bin 33009 33012: ls l /usr/bin 33009 33013: ls l /etc That output is written to stderr to not interfere with stdout. Since there are three commands, PELL has to create three children, (in this example) redirect stdout for each child, and execvp to the particular command for each child.

pipe cmd1 args1 , cmd2 args2 pipe causes PELL to create a pipe and fork a child for each cmdi. There are only two commands (however, for exta credit the maximum commands is 5). cmd1 can have stdin redirected from a file. cmd2 can have stdout redirected to a file. You will have to use dup2 to redirect the pipes. Example: pipe ls l Data , sort k5 -n > sort.out The pipe command prints each step showing a sequence, parent's process ID the child's process ID, and its command 1 33043 33045: ls l Data 2 33043 33046: sort k5 n That output is written to stderr to not interfere with stdout. Since there are two commands, PELL has to create one pipe, and two children. The pipe is the output for step 1 and the input for step 2.

Notes: 1. To redirect a file to stdin: open the filename as O_RDONLY dup2 its fd to STDIN_FILENO 2. To redirect a file to stdout: open the filename as O_WRONLY|O_CREAT|O_EXCL dup2 its fd to STDOUT_FILENO 3. Copy the files for this assignment to your execution directory: cp r /usr/local/courses/clark/cs3423/2017Fa/Proj8/* . 4. Create a directory named Dout below your execution directory. This will be useful in keeping the output in a separate directory which you can manually clean up easily (rm Dout/*). 5. Larry provided the following files: cs3423p8Driver.c

driver program which calls your functions. It also provides a simple split function and getCmdList which gets the command list from the input. It invokes your functions. Do not code your code into this file.

p8Input.txt sample command text file to exercise your code p8Extra.txt sample command text file for the extra credit. cs3423p8.hinclude file to be used by your code and the driver. makefile : used by the make utility to compile your code and create the executable, pell. To compile and create pell: $ make pell

For more information about the make utility, please see http://www.cs.utsa.edu/~clark/setup/UnixMakeUtility.pdf

6. Place your code in cs3423p8.c. It should contain at least the following functions: concCmd int concCmd(CmdList *pCmdList) This is passed a pointer to a CmdList structure which has already been populated by the getCmdList function. concCmd returns 0 if all children were launched successfully. See the description of the conc command for more information. pipeCmd int pipeCmd(CmdList *pCmdList) This is passed a pointer to a CmdList structure which has already been populated by the getCmdList function. pipeCmd returns 0 if all children were launched successfully. See the description of the pipe command for more information.

7. Extra Credit (10pts + 100 / N) Change pipeCmd to support up to five processes; therefore, up to four pipes. Managing the open/close and use of dup2 will be the challenge. Your code must meet all requirements. It should not create any zombies or orphans. Late work will not receive extra credit. Your code must meet my programming standards to be eligible for extra credit.

8. Turn in a zip file (named LastnameFirstname.zip using your name). It should contain cs3423p8.c - your source code cs3423p8.h - (if you created one) makefile - your makefile to make the pell executable. In the notes in BlackBoard, specify if extra credit was completed.