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PID: 0000 By: ael-khni
⊱ ────────────────────── {.⋅ ✯ ⋅.} ─────────────────────── ⊰
Development repo for 42cursus' ft_printf project
For further information about 42cursus and its projects, please refer to 42cursus repo.
The purpose of this project is to code a small data exchange program using Unix signals.
Create a communication program - in C - in the form of a client and server. The server is the first one to be launched, having to display its PID after. The client will take as parameters the server PID and the string to be sent. Once the string has been received by the server, this one should display it.
This communication should only be done using Unix signals. Only two signals can be used SIGUSR1 and SIGUSR2. The executable files are named client and server.
The purpose of this project is to code a small data exchange program using UNIX signals.
Keep in mind:
- You have to handle errors sensitively. In no way can your program quit unexpectedly (Segmentation fault, bus error, double free, etc).
- Your program cannot have memory leaks.
- You can use one global variable but it must be justified.
- Produce
server&clientexecutables clientmust communicate a string passed as a parameter toserver(referenced by its process ID) which then displays it- Use
SIGUSR1&SIGUSR2signals ONLY
- Add reception acknowledgement system
- Support Unicode characters
writeft_printfand any equivalent YOU codedsignalsigemptyset & sigaddsetsigactionkillgetpidmallocfreepausesleepusleepexit
Signals are standardized messages sent to a running program to trigger specific behavior, such as quitting or error handling. They are a limited form of inter-process communication (IPC), typically used in POSIX-compliant operating systems.
When a signal is sent. the operating system interrupts the target process normal flow of executing to deliver the signal. Execution can be interrupted during any non-atomic instruction. If the process has previously registered a signal handler, that routine is executed. Otherwise, the default signal handler is executed.
A signal is an event generated by the UNIX and Linux systems in response to some condition. Upon receipt of a signal, a process may take action.
A signal is just like an interrupt; when it is generated at the user level, a call is made to the kernel of the OS, which then acts accordingly.
There are two types of signals:
- Maskable: signals which can be changed or ignored by the user (e.g., Ctrl+C)
- None-Maskable: Signals which cannot be changed or ignored by the user. These typically occurs when the user is signaled for non-recoverable hardware errors.
Signal handlers can be installed with the signal(2) or sigaction(2) system calls. If a signal handler is not installer for a particular signal, the fefault handler is user. Otherwise the signal is intercepted and the signal handler is invoked.
The signals are defined in the header file signal.h as a macro constant. Signal name has started with a “SIG” and followed by a short description of the signal. So, every signal has a unique numeric value. Your program should always use the name of the signals, not the signals number. The reason is signal number can differ according to system but meaning of names will be standard.
The macro NSIG is the total number of signal defined. The value of NSIG is one greater than the total number of signal defined (All signal numbers are allocated consecutively).
The following is a list of all signals with names as in the include file <signal.h>:
No Name Default Action Description
1 SIGHUP terminate process terminal line hangup
2 SIGINT terminate process interrupt program
3 SIGQUIT create core image quit program
4 SIGILL create core image illegal instruction
5 SIGTRAP create core image trace trap
6 SIGABRT create core image abort program (formerly SIGIOT)
7 SIGEMT create core image emulate instruction executed
8 SIGFPE create core image floating-point exception
9 SIGKILL terminate process kill program
10 SIGBUS create core image bus error
11 SIGSEGV create core image segmentation violation
12 SIGSYS create core image non-existent system call invoked
13 SIGPIPE terminate process write on a pipe with no reader
14 SIGALRM terminate process real-time timer expired
15 SIGTERM terminate process software termination signal
16 SIGURG discard signal urgent condition present on socket
17 SIGSTOP stop process stop (cannot be caught or ignored)
18 SIGTSTP stop process stop signal generated from keyboard
19 SIGCONT discard signal continue after stop
20 SIGCHLD discard signal child status has changed
21 SIGTTIN stop process background read attempted from control terminal
22 SIGTTOU stop process background write attempted to control terminal
23 SIGIO discard signal I/O is possible on a descriptor (see fcntl(2))
24 SIGXCPU terminate process cpu time limit exceeded (see setrlimit(2))
25 SIGXFSZ terminate process file size limit exceeded (see setrlimit(2))
26 SIGVTALRM terminate process virtual time alarm (see setitimer(2))
27 SIGPROF terminate process profiling timer alarm (see setitimer(2))
28 SIGWINCH discard signal Window size change
29 SIGINFO discard signal status request from keyboard
30 SIGUSR1 terminate process User defined signal 1
31 SIGUSR2 terminate process User defined signal 2
- Signal (IPC)
- Process (computing)
- Thread (computing)
- How to use signal handlers in C
- signals
- How to Write Advanced Signal Handlers in UNIX
- sigaction() - IBM docs
- What is the difference between sigaction and signal?
- What is sigaction in C?
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@achrafelkhnissi| Software Engineer StudentReach out to me if you need any help or have any questions.
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