Jan Kończak os_cp

os_cp:assignments

Tue, 23 May 2023 23:25:30 +0200

Assignment 1 Deadline: May 31st. Collatz conjecture is an open mathematical problem. It boils down to a question whether the following procedure will terminate for any value of x: typedef uint64_t natural_number; void collatz(natural_number x) { while (x != 1) { // until you reach 1, if (x % 2) // if the number is odd, x = 3 * x + 1; // multiply it by three and add one, else // else, if the number …

os_cp:exec_dup

Tue, 18 Apr 2023 23:51:12 +0200

Exec… In order to run an executable file, an existing process has to 'exec' into it – that is, the process has to ask the kernel to replace its memory with the code (and data) of the executable file. So, typically to start a new process, one has to

os_cp:exercises-prog

Tue, 11 Jun 2024 14:49:36 +0200

Tentative weight for the question types: * 4 for explain a code and/or point a bug in the code. * 3 for write code or fill gaps in the code. * 2 set correct initial value for semaphores. * 3 for short, rather theoretical, questions. The weights of the topics in the test will be scaled to the number of lab classes for the topic, i.e., questions worth about half of the points will deal with course materials from classes 7-9 covering threads, mutexes and condition variables (that is three…

os_cp:exercises-shell

Thu, 16 Apr 2026 01:24:31 +0200

In the exercises, one may also provide names of interactive programs (e.g., htop for process management, but if one chooses so, then one has to specify what needs to be done after starting the program in order to solve the exercise. For instance, if the exercise states

os_cp:files_processes

Thu, 12 Mar 2026 01:00:23 +0200

Copying, moving and erasing files touch file echo contents > file fortune > file touchecho> cat filename Directories mkdir dir creates a new directory. mkdir -p dir1/dir2/dir3dir1dir2dir1dir3dir1/dir2 -pmkdir To remove an empty directory one can use

os_cp:find_out_what_is_going_on

Wed, 10 May 2023 02:04:59 +0200

Yet another reason that makes concurrent programming harder. Below, there is a piece of code that can be compiled by issuing: gcc -g -O0 sb.c -o sb The program forks and uses shared memory, so concurrency is involved. Analyze the code and tell which results can be output.

os_cp:find_out_what_is_going_on2

Tue, 28 Apr 2026 00:29:12 +0200

Yet another reason that makes concurrent programming harder. Below, there is a piece of code that can be compiled by issuing: gcc -g -O0 sb.c -o sb Analyze the code and tell which results can be output. Remember that global variables are by default zero-initialized.

os_cp:fork_exec_pipes

Mon, 19 May 2025 22:27:10 +0200

Fork Forking To create a new process, POSIX defines the fork function: pid_t fork() fork creates a copy of the running process. Upon success, fork returns the pid of the child process in the parent process, and the value of

os_cp:intro

Thu, 12 Mar 2026 00:57:09 +0200

Introduction A bit of history Terminal and console were a piece of hardware that let you interface with a computer. * terminal: a combination of a keyboard and output device (such as a video display unit) by which data can be entered into or output from a computer or electronic communications system

os_cp:locate_find

Tue, 31 Mar 2026 14:08:42 +0200

FHS Filesystem Hierarchy Standard hier file-hierarchy man hier /bin/usr/bin/sbin/usr/sbin /lib/usr/lib /usr/share /etc /opt /root/home /tmp /var Searching files locate The locate tool looks up words or wildcard expressions provided as arguments in a previously generated list of files.

os_cp:open_fork

Tue, 11 Apr 2023 23:43:27 +0200

Creating, opening and closing files To create or open a file, POSIX defines: int open(const char *pathname, int flags) int open(const char *pathname, int flags, mode_t mode) and a creat function that is a shorthand to open(pathname, O_WRONLY|O_CREAT|O_TRUNC,

os_cp:pipes_signals

Tue, 09 May 2023 23:18:49 +0200

Blocking vs non-blocking operations Most POSIX functions complete in a limited number of steps. But when the user invokes certain functions, then in well-defined circumstances it makes sense to wait until a particular thing happens. For instance, when a

os_cp:prog_assignment

Tue, 21 May 2024 21:01:43 +0200

os_cp:prog_filebasics_signals

Wed, 14 May 2025 18:20:15 +0200

POSIX POSIX – the Portable Operating System Interface standard – apart from standardising shell and utilities, it also defines functions, macros, and external variables to support applications portability at the C-language source level. POSIX specifies what should be present in the

os_cp:prog_intro_read_write

Tue, 11 Apr 2023 23:39:22 +0200

Warm-up Create a program, compile it under the name prog. Print a static text with: * C standard I/O library (#include ): * printf, * fprintf, * POSIX write function (see man 3p write) that is made available by #include

os_cp:redirects_pipes

Tue, 24 Mar 2026 14:33:17 +0200

Outputting file / text / sequences Printing file contents cat [file]... outputs input files one after another or outputs the standard input if no files are specified. Name comes from concatenate. cat numbers lines with the -n switch and outputs non-printable characters as

os_cp:scripting

Wed, 08 Apr 2026 22:53:28 +0200

Creating a shell script (Non)interactive mode The login shell in a terminal emulator runs in interactive mode. When the shell executable is invoked with a file as its argument, it runs in non-interactive mode, and reads the commands from the file rather than the standard input.

os_cp:semaphores

Wed, 10 May 2023 02:23:29 +0200

Semaphores What is a semaphore A semaphore is a mechanism to control concurrency. It has an associated number that can be concurrently incremented and decremented by multiple processes / threads. Incrementing a semaphore is instantaneous, and so is decrementing a semaphore which value is positive.

os_cp:shmem_semaphores

Wed, 04 Jun 2025 19:47:22 +0200

Shared memory It is possible for two processes to use the same physical address range of the main memory. Obviously any modification to such memory done by one process is visible to the other processes that access the memory. Such memory is called

os_cp:tba

Thu, 06 Mar 2025 14:06:46 +0200

Editing the command line Bash (as well as numerous other programs) uses the readline library to read commands from standard input. Lots of software use for the same purpose the libedit library due to licensing reason. The readline library is renown for providing comfortable, efficient and powerful editing capabilities within the input line as well as its built-in support for history of previously read lines.

os_cp:threads

Fri, 25 Apr 2025 13:55:42 +0200

Threads A process can run multiple threads – multiple flows of control. In general, the threads share all resources (such as memory or open files). Each thread uses a separate stack, and obviously has its own state of the CPU registers. A limited set of properties might also be specific to a thread (e.g., signal mask, CPU affinity).

os_cp:users_permissions

Wed, 18 Mar 2026 21:56:34 +0200

Users and groups In Unix-like systems there are users and groups. A user is identified by a numerical user identifier – uid. Uids are mapped to usernames. A group is identified by a numerical group identifier – gid, that are likewise mapped to group names.