- GCC compiler
- Ubuntu
From the root directory of project, run make followed by ./a.out.
NOTE: Each .c file of function has it's corresponding .h file in which function prototype is defined.
- Welcomes user with welcome message :p.
- reads previous history from history.txt file.
- calls the display function for to print prompt.
- takes the input and updates the history.
- tokenize on the basis of ;.
- calls the functions based upon the input user enters.
- prints the history onto file if user press exit.
- If input is just space/ tabs the program continues to run ie asks user for next input ignoring space / tab entered previously. -Maximum size of input assumed to be MAX_LIMITS is 2000.
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Counts the total ampercant and tokenize on basis of ampercant.
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After this tokenize on basis of tab and spaces.
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Compare total ampercent with no of commands seperated with & then all are background else you have last as foreground and rest of background.
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compares command with echo/ls/discover/history/pwd etc and calls corresponding functions.
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When user enters "exit" then prints the last 20 processes onto history file
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If command matches with none of defined processes then execvp runs it else commmand is declared invalid.
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It runs the foreground and background processes by forking and providing each background process with pid and printing adequate error .
&(used for running process in background) can come anywhere in command. -
REDIRECTION was taken care of by considering all three cases and adequately redirecting them using dup2 and stdout/stdin.
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PIPELINE so pipeline is redirecting output of one command to another as input inbilt pipe function was used for the same.
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SIGNAL HANDLING
- CTRL C: handled via sendling signal SIGINT , on going fg process is terminated.
- CTRL Z: handled via SIGTSTP / WIFSTOPPED. Here fg process is sent to background and its status is set to stopped.
- CTRL D: check by the empty buffer. ONce detected , user is logged out of terminal.
- If prompt doesn't appear due to any reason press "ENTER"
- If you want to exit the program ie exit the shell don't forget to enter "EXIT" since it updates the history.txt.
- IN fg prompt total time of all fg processes is printed.el sleep 2 ; sleep 4 & sleep 6 will give took 8.(6+2)
- In redirection it's asssumed that there will be appropriate spaces.
- Prints prompt onto the screen make use of inbuilt functons like getcwd, gethostname, geteuid for user id .
- Checks for terminated child processes in case background process runs.
- Prints appropriate statement onto screen depending on how to process has exited.
- In case we have foreground process and it takes more than 1 sec to execute then prompts prints the time along on just next prompt.
- Prints tokenized arguments given after echo onto screen.
- Any multiple spaces and tabs are ignored ie tokenized.
- Example echo hi (double tabs) fine is printed as hi fine.
- prints the present working directory onto the screen.
- prints the desired information onto screen which includes the process status such as S(Static)/R(R+ : running), virtual memory.
- Information was extracted from /stat/ , /prc/ , /exec/ files via use of /status/ etc
- 4th and 7th value helps checking if the process is fore ground or not. -for when no argument is passed along with pinfo then getpid() gives you the value of pid of current running shell.
- Navigate to different directories depending on users input
- cases of navigating to existing folder, home directory , '.',"..","~","-" etc are handled.
- Prints all files/sub-directories in a location.
- Flags implemented:
aandlwhere a corresponds to printing "." and "..". - Multiple directories supported.
- SCANDIR used for scanning file via struct dirent
- Prints the minimum of (total commands entered, 10). Three functions work together for history these are read history from the history.txt file for previous executon , secondly write_history this regularly updates the history depending on command entered by user given not same as previous command.
- Last recent 20 commmands are stored in history.txt file.
- NOTE before exiting any process one must enter "EXIT" because i put condition of writing onto file in this since you require txt file for next process.
- print all the content of directory given.
- in case no directory specified , home directory is assumed to be directory
- flags '-d' and '-f' were implemented for directory and files.
- IN discover if -d flag is there the file / file search won't be there since only since d flag.
- Order should be considered fro input directory flags file name
- if some file is searched then only its path is printed depening on flags (-f) should exist.
- it takes two parameter that is the serial numer og the job and signal number
- on getting a signal a corresponding kill is generated
- for knowing the job number user must enter the command : jobs first since ordering might change with time depending on executed commands.
- it prints the list of all process in background
- takes flag as "-r" and "-s" where r is to print all running processes and "-s" for stopped , structure was used and was sorted on basis of q sort.
- Serial number of commands may keep varying from command to command as user might enter command such as "fg" which changes array by removing a process.
- it brings the process at given serial number to foreground and executes it.(state changed to runnning)
- once a process is brought ot foreground , its deleted from background array and hence the jobs are reordered.
- not considered mentioning the time took for this case.
- it runs the given job number process in background.
- Process runs like a normal background process and terminates .
- Once terminated it's instance is removed from background array.