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For Rutgers CS214 Systems Programming Project 3
Ron Cohen (rc1456) and Enrico Aquino (eja97)
Type or copy and paste the following commands into the terminal after downloading
tar -xf your-p3.tar
cd P3
makeStart the Mysh
./myshRun the program using batch mode
./mysh `<commands/file>`When making this program, gradually tested each command from the normal shell (cd, ls, echo, which, etc.) to see what the problems were and fix them accordingly. For example, with cd we made sure it found the desired directory and we made sure it changed to the correct directory in the parent process not the child. If the directory didn't exist, we printed an error but continued the progam. Same with ls, we make sure it was reading and printing the files and folders of the current or desired directory. We continued to do this with different commands to make sure they were working properly. After they were working, we then commands like ls -a to make sure it can read the -a option was working. We tested other commands to make sure their options were working.
For step two of the project, we moved on to test piping and redirecting. First thing we had to do was was make sure | was being read. We would feed mysh commands like echo hi | echo hello and echo hi|echo hello to make sure the pipe is working as intended. We then used other commands with piping to see if they were functioning properly. From there, we began testing redirecting. We started off by sending outputs, > of various commands like echo, cat, and ls to files we have created. Afterward, we began work on inputs, <. Same with output, we tested various commands to see if it as working correctly. From there, we combined piping and redirecting in several different commands.
In the final stages of our project, we began working on batch mode. We first made sure that mysh was able to read the file we were piping to it. Once mysh was being read files properly, we then moved on to see if commands could be read properly from the script we made, hello.sh. With this we were also able to see how then-else statements were working.
We tried to fix any errors if they are fixable such as ignoring invalid redirection, ingnoring invalid pipes. This ignores redirections back to back such as <<, >>, <>, or <>.
Redirection will also use the last redirection for that command. Example echo hi > a > b. It will print hi into b.
If there is nothing before a pipe/pipe starts the command it ignores it. If there is a pipe at the end of a command, it takes the output from the previous program and prints nothing.
If there is a pipline and one of the commands are invalid, it will print an error into the stdout for that process and continue on with the pipeline.
ls | wc -w expected around 15
ls | wc -w | wc -w expected 1
ls | grep . | sort | uniq -c | wc -l expected about 15
echo hi | echo hello expected only hello
cd .. | pwd expected printing out previous dictionary
cat < a expected "echo hello world"
echo a file > a.txt expected truncate file a write "a file"
ls > a | sort < a | uniq -c | wc -w > b expected truncate files and write file list in a and word count in becho hello world expected "hello world"
then echo this should run expected "this should run"
else exit whoops This should not exit the program
echo this should also run expected "this should also run"
echo hello world expected "hello world"
then echo this should run expected "this should run"
else exit whoops This should not exit the program
then echo this should also run expected "this should also run"