Basic Linux shell utility commands are implemented on the xv6 operating system, for which functionality is not provided for.
- ps - Lists out all processes in either sleeping or running state
- clear - Clears screen (only when qemu is run on the terminal itself)
- exit - Exits from the emulator
- touch - Creates a temporary new file for the duration of the current session
- wc - Displays number of newline characters, number of words, size of file in bytes and name of file
Execute:
make qemu-noxor:
make qemu-nox-gdb make qemucan also be used. However, the commands will be mirrored on both the existing terminal and the new emulator window opened. Also, the clear command will not work on the emulator, but will work on the existing terminal.
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The ps and exit commands are implemented as system calls, thus their actual codes are present in the sysfile.c file.
- The ps command accesses the process table, which is only accessible in the proc.c file. Thus, the system call calls a function from proc.c, called proc_deets. (Also, an additional structure member needs to be added to the process table, in the proc.h header file, as: int priority;)
- For the exit command to work, an additional line of code has been added to the Makefile under the QEMUOPTS heading; refer.
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Files pertaining to system calls are as follows:
- syscall.c
- syscall.h
- sysfile.c
- user.h
- usys.S
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Any new user program (assume prog.c) to be added to xv6 need to be added to the Makefile under the following heads:
- UPROGS: _prog\
- EXTRA: prog.c\
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The programs for the commands to be implemented have already been added into the Makefile (above steps are for any other user programs to be added).
Only user programs files are to be newly added into the 'xv6-public' folder; the rest of the files are provided as a reference to modify/add to the contents of the pre-existing files. Take note of the differences in the files provided and the already existing files, and modify the system call and process related files, and the Makefile accordingly.