23.c

/*
============================================================================
Name : 23
Author : Piyush Singh
Description : Write a program to print the maximum number of files can be opened within a process and
size of a pipe (circular buffer).
Date: 25th Sep, 2025.
============================================================================
*/

// Program: Show max open files per process and pipe buffer size

#include <stdio.h>      // For printf(), perror()
#include <stdlib.h>     // For exit()
#include <unistd.h>     // For pipe(), sysconf()
#include <sys/resource.h> // For getrlimit()

int main() 
{
    // Part 1: Max number of open files per process
    struct rlimit limit;
    if (getrlimit(RLIMIT_NOFILE, &limit) == 0) 
        printf("🔢 Max open files per process: %llu\n", (unsigned long long)limit.rlim_cur);
    else 
        perror("❌ getrlimit failed");

    // Part 2: Pipe buffer size
    int pipefd[2];
    if (pipe(pipefd) == -1) 
    {
        perror("❌ Pipe creation failed");
        exit(1);
    }

    // Use fpathconf to query pipe buffer size
    long pipe_size = fpathconf(pipefd[0], _PC_PIPE_BUF);
    if (pipe_size != -1) 
        printf("📦 Pipe buffer size (bytes): %ld\n", pipe_size);
    else
        perror("❌ fpathconf failed");

    close(pipefd[0]);
    close(pipefd[1]);
    return 0;
}

/*
Output:
╰─ ./23                                                                       ─╯
🔢 Max open files per process: 256
📦 Pipe buffer size (bytes): 512
*/