cshell

Based on a coursework on low-level programming of Operating Systems. This is ment to be executed in a Linux environment

Quick start

Compile

make

Execute

./shell

Commands

Basics

• autores [-l] [-n] Prints the authors' details

  • -l prints the logins
  • -n prints the names

• pid [-p] Prints the PID of the process executing the shell

  • -p prints the PID of the parent process

• fin or end or exit Ends the shell

File systems

• info [file1] [file2] ... Givesinformation about the files or directories supplied as arguments.

• recursive [ON | OFF] Enables or disables the recursivity in the behaviour of the command list.

• list [-l] [file1] [file2]... Prints the PID of the process executing the shell. * -l lists the files and directories with more information

• eliminate [-f] <file*name> Removes a file or a directory. * -f if it is a directory, it removes all contents

Memory

• malloc [-deallocate] [size] Shows the allocated memory using this command. If size is specified, the shell allocates size bytes of memory, showing the memory address of the allocated memory. * -deallocate It deallocates a block previously allocated of size bytes

• mmap [file*name] [permissions] This command maps a file in memory with the permissions in rwx format without spaces. If no filename* is specified, the allocated files are listed.

Example: --> mmap textfile.txt rw

• sharednew [k] [size] Creates a shared memory of key k and allocates it in the process address space. If no arguments are specified, sharednew will list the addresses allocated.

• shared [-deallocate] [k] Gets the shared memory of key k and allocates it in the process address space. If not arguments are specified, shared will display the addrsses allocated. * -deallocate It deallocates a block previously allocated with key k

• rmkey <k> Removes the shared memory region with key k. It is not produced any deallocation of memory.

• allocation Shows all allocated memory.

• deallocate [addr] Deallocates the memory allocated in the address add.

• mem Prints the memory addrsses of three program functions.

• memdump <address> [count] Prints the contents of a memory address. If count is specified, it prints count bytes.

• recursivefunction <n> Function that shows how the recursivity works. This function is calling itself n times.

• read <file> <addr> [count] Reads count bytes of file file into the memory address addr. If count is not specified, the whole archive is read.

• write <file> <addr> <count> [-o] Writes to the file file the contents of address addr. The amount of bytes written are specified in count.

  • -o If the file exists, overwrite it.

Processes

• setpriority <pid> [value] Sets the priority of the process with PID pid to value. If value is not specified, setpriority will show the priority of the process with PID pid.

• fork The shell creates a child process executing the same code: it creates a child shell. The parent shell waits for the child to terminate.

• searchlist [+<dir> | -path | <exfile>] Lists the directories where the shell searches for executable files.

  • +<dir> It adds a directory to the search list.
  • -path The directories in the environment variable PATH are added to the list.
  • <exfile> Searhes for exfile in the search list and shows the complete path where the executable file is.

• exec <program> [arg1 arg2 ...] [@<priority>] Replaces the shell code and executes the program program with priority (if specified) priority.

• <program> [arg1 arg2 ...] [@<priority>] Executes the program program in the foreground with an optionally specified priority.

• background [arg1 arg2 ...] [@<priority>] Executes the program program in the background with an optionally specified priority.

• jobs Lists the processes running in background of the shell.

• proc [pid] Shows the information of the process with PID pid.

• clearjobs Empties the list of background processes.

Licence

Source code can be found on github, licenced under GPL-3.0.

Developed by Martiño Rivera and Carmen Corrales