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Category Archives: Linux Internals and System Programming

Time calls in system Programming.

In system programming it is very important to know the current time of your system ,Because you will be often needed to use that information i.e every time when you create any File or Directory and then you want to … Continue reading

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How to Send a signal -Using Kill command

Send a signal by Kill command ======================= – To send a signal to a process other than current task. – It has prototype :- int kill(pid_t pid, int signo); – It is included using header :- #include<signal.h> – The system … Continue reading

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How to register a signal

Register a signal ================== – Program can handle a signal using signal library function signal(). – signal() is used to register the signal handler function with kernel on behalf of current process. – It is included in header :- #include<header.h> … Continue reading

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About Signals

Signals ======== – A signal is an event generated by UNIX/LINUX system in response to some condition. – On receipt of a signal, process may in turn take some action. – Signals are generated by some error conditions such as:- … Continue reading

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Replacing a Process Image

Replacing a Process Image ========================= – The exec function replaces current process with a new process. – The path of new process is specified as argument to exec. – It is defined in header : #include<unistd.h> – Last argument of … Continue reading

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Orphan Process

Orphan Process =============== If in a process, the parent process is terminated before the child process, the child process become orphan – It takes the lowest possible process as its parent – And its PPID is changed to the PID … Continue reading

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Zombie or Defunct Process

Zombie or Defunct Process ========================== If a child proces tries to teminate,its association with parent remains until the parent terminates normally or calls wait. – The child process entry in process table is therfore not freed up immediately. – Althougth … Continue reading

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waiting for a process

Waiting For a Process ===================== – Sometime we would like to find out when a child process has finished. – It is needed for parent process to wait until the child finishes before continuing by calling wait. – It has … Continue reading

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Process Duplication using fork

Process Duplication using system call fork ============================== – A new process is created using fork(). – fork() is a system call. – fork duplicates the current process. – It creates a new entry in the process table with many of … Continue reading

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THE LINUX FIRE WALL

  If we talk about firewall the first thing that comes to our mind is a software “Barrier” between a system and a network it may be either internal or external. The purpose of this software is to protect our … Continue reading

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Inter process communication using pipe successfully done.

RCS file: header.h,v Working file: header.h head: 1.2 branch: locks: strict root: 1.2 access list: symbolic names: keyword substitution: kv total revisions: 2; selected revisions: 2 description: This is header file include stdio.h stdlib.h sys/types.h unistd.h —————————- revision 1.2 locked … Continue reading

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inter process communication using file successfully done.

RCS file: header.h,v Working file: header.h head: 1.2 branch: locks: strict root: 1.2 access list: symbolic names: keyword substitution: kv total revisions: 2; selected revisions: 2 description: Header file —————————- revision 1.2 locked by: root; date: 2015/02/26 14:25:18; author: root; … Continue reading

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CREATING STATIC LIBRARY

Static libraries are collection of ordinary object files. For a static library, the actual code is extracted from the library by the linker and used to build the final executable at the point you compile/build your application. Steps: 1.Creates .c … Continue reading

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an overview of how the system call in linux works

0) There is global system_call_table which has offsets of every system call provided by the kernel (system call is just some function inside kernel). The global means every process share the same system_call_table 1) User software prepares arguments of the … Continue reading

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Kernel Space and User Space Understanding of Kernel space and User space in detail is very important if you wish to have a strong base of Linux Kernel. Here Kernel Space and User Space corresponds to their Virtual address space. … Continue reading

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