Victor Denisov's Blog

A Blog About Programming

Linux Programming #1

This is the synopsis of the first Linux programming lab.

The description of the problem to be solved

During the whole course one problem should be solved: restore a password from a hash code generated by htpasswd command. The password should be restored using several approaches:

  • recursive brute force,
  • iterative brute force,
  • multi threaded brute force on a machine with several CPUs,
  • distributed over the network brute force.

The roadmap of the course

  • Hello world application.
  • Recursive brute force solution.
  • Iterative brute force solution.
  • Multi-threaded brute force solution.
  • Synchronous thread per client solution.
  • Asynchronous thread per client solution.
  • Reactor implementation.

Topics covered in the first lab

  • Linux shell commands introduction.
  • Source code editor.
  • Hello world application.
  • Stages of program compilation.
  • Primitive Makefile for the hello world application.
  • GNU coding standards

Linux shell commands introduction

Bash reference manual

The commands used during the lab are:

  • mkdir - create a directory,
  • cd - change a directory,
  • rm - remove a file,
  • ls - list content of a directory,
  • gcc - compile source code,
  • make - run make utility,
  • ./hello_world - run the hello world application.

Source code editor

GNU Emacs manual

Emacs is one of orthodox editors for C programming.

Here is a list of the most often commands for editing in Emacs:

  • C-x-f - open file
  • C-x-s - save file
  • C-x-b - switch buffer
  • C-x-u - undo
  • C-space - set mark
  • A-w - copy
  • C-w - cut
  • C-y - paste (yank)
  • C-e - end of line
  • C-a - beginning of line
  • C-A-q - indent block
  • Esc-Esc-Esc - escape
  • C-q - cancel key sequence
  • A-x - run command:
    • shell - run bash,
    • compile - run make,
    • grep - run grep,
    • replace-string - replace.

Hello world application

Solution that was implemented by the end of the first lab:

#include <stdio.h>
#include <stdlib.h>

main (int argc, char * argv[])
  printf ("Hello world\n");
  return (EXIT_SUCCESS);

Stages of program compilation

GCC manuals You can determine the version of your gcc using command:

gcc --version

Stages of compilation.

  • preprocessor - the result is source code file,
  • translator - the result is object file,
  • linker - the result is executable file.

The command line used to compile the application.

gcc -g -o hello_world -Wall -Werror -O2 hello_world.c

Make utility

GNU Make manual

The Makefile used to compile the application

all: hello_world

CFLAGS+= -g -Wall -Werror -O2

GNU coding standards

The GNU coding standards


  • The C Programming Language. Kernighan, Brian W.; Ritchie, Dennis M.
  • The Practice of Programming. Kernighan, Brian W.; Rob P.
  • Advanced Programming in the UNIX Environment.
  • Richard Stevens; Stephen A. Rago
  • The Unix Programming Environment. Kernighan, Brian W.; Rob P.
  • The Art of Unix Programming. Eric S. Raymond
  • Advanced Linux Programming. Mark Mitchel; Jeffrey Oldham; Alex Samuel
  • The Linux Programming Interface: A Linux and UNIX System Programming Handbook. Michael Kerrisk
  • The Standard C Library. Plauger P. J.
  • UNIX Network Programming, Volume 1: Networking APIs: Sockets and XTI.
  • Richard Stevens
  • UNIX Network Programming, Volume 2: Interprocess Communications.
  • Richard Stevens