Linux Userspace C Programming

Linux Userspace C programming

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System calls.

"wait" system calls

 Introduction to Wait System call

 C Program to create a Zombie child when the parent exits without "wait" system call.

 C program where parent process waits for it child to exit (using wait system call) and prints the exit status.

 C program where parent waits for the child to terminate via termination signals and prints the termination status

 C program on "waitpid" system call usage [WIFSTOPPED, WIFEXITED, WIFSIGNALED,WCOREDUMP]

 C program on "waitpid" system call usage [WIFSTOPPED and WIFCONTINUED]

 C program where parent returns the exit status of child in it’s SIGCHLD signal handler.

"exec" system call

 C program on how to use execv and execvp system calls

"fork" system call

 C program to use clone system call

 Introduction to Daemon-izing a Process in Linux

 C Program for single parent and 26 child process forked by the single parent

 C program to Daemonize a Process in Linux

"fcntl" system call

 C program on fcntl system call usage with flag F_GETFL

 c program to implement file locking in a process

"dup" system call

 C Program to show that child inherits parent file descriptors on fork

 C program on how to use "dup" system call

Inter Process Communication

 C program 2-way Client server Unix domain UDP socket communication

 C program to implement message queue in linux

 C program for client-server UNIX domain socket where transmitted message is in structure form

 C program to establish IP TCP socket from one server machine to another client machine

 C program on socket programming for connecting Multiple clientsto Server over TCP internet socket

C program for System V Message Queue vs Unix Domain socket, 50000 messages 'send' timestamp capture

openssl library applications, Encryption C programs

 Handy Notes on SSL handshake betweenclient and server

 POC on mutual authentication for client (wget command) and server (apache server ssl)

 C program for Secure Client-Server SSL authentication using OpenSSL library

 C program on encrypting, encoding, decoding and decryption of Password using Openssl library

 C program on base64 encoding and decoding using openssl Library

C program on Encrypting Passwords using crypt()

Raw Socket programming

 C program to create ICMP echo packet and receive ICMP reply packet

Process Synchronisation Mechanisms

Introduction on Thread Synchronization Problems

 Introduction to Mutex vs Semaphore

 Why to use Volatile Keyword and Volatile vs process synchronisation mechanisms (Like mutex lock and semaphores)

 C Program to implement Multi-threaded program

 C program to make process sleep by using sem_wait and wake it up by doing sem_post in SIGTERM signal handler

 C program to apply "named" semaphore lock on share resource between independent processes

How to avoid Common Semaphore Errors

C program on How to use Mutex lock in multi-threaded applications

 C program to use spinlock to block the process at a point and unblock it by sending SIGALRM which will unlock the spinlock

Signal Handler

 Introduction on how to "signal" system call

 C program on how to use sigaction system call

 Code for Parent process registers for SIGCHLD and waits in the signal handler for Child process to die

 C program to change to default action inside the signal handler

 C program to send signal (SIGTERM) from the signal handler(SIGINT) of one process to another process which is registered with SIGTERM

 C program on How to handle SIGSEGV, but also generate a core dump

C program to print the PID of the sender process that sends signal to receiver process

Random Handy C Programs

 C program to encrypt and decrypt a password

 C program to convert "integer in string" into integer without using atoi

 C program to print userid and group id of a process

 C program to implement error handling

 C program to parsing a string with delimiter in-between [using strtok]

 C program to write environment variables and their values into file and read the variables and their values from the file (using strtok)

 C program to copy values from double pointer array into file

 C program to write into file from array and read from the same file back into the array

 C Program on how to use "umask" system call

 C program on how to use command line arguments in main function

 C program to write 2 -D array into file (one string on each line of file)

 C program to Convert "integer in string" to actual Integer using "strtol" library function

 C program to print error code, if directory is already present [system call: mkdir]

 C program for Frame encapsulation and decapsulation using strtok

 C program for create a macro for vprintf

 C Program for finding a file in the directory

 C program to find pid of a file

 C program on how to use strtok

 C program to check whether file is empty or not

 C program to write structure values in file and read it back into another structure from the same file 

C program to print to the next line in file in each iteration

C Program to save address of a pointer in a variable

Timer Programming

 C program to calculate the time difference between 2 time stamps

 C program to get system Uptime and print hrs, mins, day etc..

 C program to print system uptime

 C program to implement software timer

 C program to print current time in hrs, mins , secs and "Milliseconds"

 C program to extract the seconds from "system uptime" command

 C program to define macro PRINTF for printf , where in PRINTF takes same arguments as printf and also prints timestamp

 C program to sort file in ascending or descending order on the basis of date and timestamp, which are embed into filename

Function Pointers

 Introduction to Function Pointers

 C program on using "function pointers" in a structure

Backtrace

How to generate backtrace, when a c program crashes with SIGSEGV

Kernel Programming

 C program and Makefile on how to build, insert and remove kernel module from linux kernel

 C program for passing kernel address to system call in Kernel space

Makefile

 How to write a simple Makefile for a simple project

 write make file for dynamic linked libraries

 C program on How to link dynamic and static libraries [Makefile changes]

Handy Linux tools and commands

1. vimdiff shortcuts

2. Hand Gesture Recognition git hub code location