Listing files recursively in C in a menu with scroll.

One of the most complex programs I've ever written which makes use of my latest development with list boxes in C. You can navigate and change path while the different files and directories in the new path are added to the dynamic list for scroll.

>> SOURCE CODE <<

Segmentation Fault - C Pointers

Segmentation Fault!!!

I have seen this phrase so many times I may end up having nightmares with it. But I got there in the end!! In my experience,  it seems the only way to learn how to use pointers properly is through trial and error. :D

This time I've used them to develop a ListBox in C with scroll capabilities.

As usual you can find it in my github repository. (Code available for Linux, Windows and DOS).

Cheers!

Demo:

C-Edit (In progress)

I'm working on developing an editor in C for Linux in the fashion of the old MS-DOS edit.com.
Features (so far):

• Double screen buffer in memory for greater display control.
• ANSI functions for changing color output, hide cursor, box-like characters, etc.
• No Ncurses. 
• Kbhit() so that I can loop without stopping the program (eg: display current time).
• Drop-down menus with a circular linked list.

You can find it on my Github Page. Screen caps:

A Very Simple Double Screen Buffer

The reason for creating a screen buffer is to have greater control over how things are displayed on  screen. It acts as an 'intermediary' step in memory before printing the final result to the terminal. If you have another copy of the buffer in memory, you can revert to previous stages.

Imagine you want to display a window to the user. Before doing so, you push the current screen to the old buffer. You show the new screen with the window on it and finally you pop or recover the previous screen from the old buffer. If you just update to screen the characters that have changed you can avoid any flickering effects that will come about by updating the whole screen every time.

In the old days of DOS, this could be achieved by accessing an absolute address in memory $B800:$0000.

[Old buffer] ----> [Current Buffer] -----> [Final Display]

To create the buffer, we need to know the terminal dimensions in rows and columns. (See previous post). Because the terminal dimensions vary, we cannot predict before execution how large the buffer will be. That's why we need a dynamic structure in memory. My version uses a single linked list composed of cells. Each cell accounts for every 'pixel' on screen and records some attributes in a structure form -  namely, the character to be displayed along with its background and foreground colors. The size of our list will be determined by rows x columns. This representation in memory of the screen will need subroutines to control the display. Everything you want to show on screen will be printed to the buffer first. Then the update routine will finally show the final composition to the user. An additional buffer, called old_buffer, will help us revert to previous screens so as to show, for instance, a window area to the user and then closing it without affecting the text or screen portion that was behind it prior to the window being shown. The next step will be to create dynamic windows that store the information behind them in their structure. 


Structure detail + Screen caps:

Dropdown menu in text-mode/terminal coded in C for linux.

Source code:
https://mega.nz/file/cP1ABB5Z#IgZ2C-rR8R6Tw3LoLao8EMJbaIXTkKjNvrQk3KEpajw

Instructions: Download, uncompress and type make to build. Execute: ./test1

YET MORE ANSI FUNCTIONS + TERMINAL DIMENSIONS

I'm working on creating a double screen buffer in C to have greater control of the display on the terminal. In the meantime, more useful functions useful to that end. :)

Show/Hide cursor:
void hide_cursor()
{
  printf("\e[?25l");
}

void show_cursor()
{
  printf("\e[?25h");
}

Draw box-like characters on Linux Terminal:

ASCII characters change from 106 to 121.

printf("%c(0", 0x1b); // Border chars on

printf("%c(B", 0x1b); // border chars off

Get Terminal Dimensions:

#include <sys/ioctl.h>
#include <stdio.h>

struct winsize max;
int get_terminal_dimensions(int *rows, int *columns)
{
//Get dimensions of screen and pass them by value.
  ioctl(0, TIOCGWINSZ , &max);
  *columns = max.ws_col;
  *rows = max.ws_row;
   return 0;
}

C POINTERS - CIRCULAR DOUBLY LINKED LIST

A Simple Selection Menu in C with Ansi functions. 
This time I'm working on creating a circular list with pointers so as to display choice menus in C using colors to highlight the items. 

In my implementation, I have used 3 external global pointers (head, former and tail). That probably means that I can only create one list as these pointers are global variables.

#include <stdio.h> #include <stdlib.h> #include <string.h> #include <termios.h> #include <unistd.h> #include <sys/ioctl.h> /* Last modified : 19/9/2017 Coded by Velorek. Some of the terminal routines from: https://stackoverflow.com/questions/7469139/what-is-equivalent-to-getch-getche-in-linux Circular linked list to make a selection menu in C. Target OS: Linux. */ // Background colors low intensity #define B_BLACK 40 #define B_RED 41 #define B_GREEN 42 #define B_YELLOW 43 #define B_BLUE 44 #define B_MAGENTA 45 #define B_CYAN 46 #define B_WHITE 47 // Foreground colors low intensity #define F_BLACK 30 #define F_RED 31 #define F_GREEN 32 #define F_YELLOW 33 #define F_BLUE 34 #define F_MAGENTA 35 #define F_CYAN 36 #define F_WHITE 37 // Background colors high intensity #define BH_BLACK 100 #define BH_RED 101 #define BH_GREEN 102 #define BH_YELLOW 103 #define BH_BLUE 104 #define BH_MAGENTA 105 #define BH_CYAN 106 #define BH_WHITE 107 // Foreground colors high intensity #define FH_BLACK 90 #define FH_RED 91 #define FH_GREEN 92 #define FH_YELLOW 93 #define FH_BLUE 94 #define FH_MAGENTA 95 #define FH_CYAN 96 #define FH_WHITE 97 #define TRUE 1 #define FALSE 0 typedef int BOOL; /* Global Variables */ struct winsize max; static struct termios old, new; int rows, columns, old_rows, old_columns; typedef struct _listchoice { int index; // Item number int backcolor0; // Back and Fore colors when not selected int forecolor0; int backcolor1; // Back and Fore colors when selected int forecolor1; int wherex; // Position of the item int wherey; char *item; // Item string struct _listchoice *next; // Pointer to next item struct _listchoice *back; // Pointer to previous item. } LISTCHOICE; LISTCHOICE *head=NULL; LISTCHOICE *tail=NULL; LISTCHOICE *former=NULL; LISTCHOICE *mylist=NULL; /* Terminal manipulation routines */ void gotoxy(int x,int y) //Sets the cursor at the desired position. { printf("%c[%d;%df",0x1B,y,x); } void outputcolor(int foreground, int background) //Changes format foreground and background colors of display. { printf("%c[%d;%dm", 0x1b,foreground,background); } void screencol(int x) { //change color of entire screen gotoxy(0,0); outputcolor(0,x); printf("%c[2J", 0x1b); outputcolor(0,0); } /* Initialize new terminal i/o settings */ void initTermios(int echo) { tcgetattr(0, &old); /* grab old terminal i/o settings */ new = old; /* make new settings same as old settings */ new.c_lflag &= ~ICANON; /* disable buffered i/o */ new.c_lflag &= echo ? ECHO : ~ECHO; /* set echo mode */ tcsetattr(0, TCSANOW, &new); /* use these new terminal i/o settings now */ } /* Restore old terminal i/o settings */ void resetTermios(void) { tcsetattr(0, TCSANOW, &old); } /* Read 1 character - echo defines echo mode */ char getch_(int echo) { char ch; initTermios(echo); ch = getchar(); resetTermios(); return ch; } /* Read 1 character without echo */ char getch(void) { return getch_(0); } /* Read 1 character with echo */ char getche(void) { return getch_(1); } int get_terminal_dimensions(int *rows, int *columns) { //Get dimensions of screen by value. ioctl(0, TIOCGWINSZ , &max); *columns = max.ws_col; *rows = max.ws_row; return 0; } /* Dynamic List routines */ void add_item(LISTCHOICE *list_identifier, char *str, int x, int y,int bcolor0, int fcolor0, int bcolor1, int fcolor1) { LISTCHOICE *newp; if (head == NULL && list_identifier == NULL) { //Reserve memory list_identifier = (LISTCHOICE *) malloc(sizeof(LISTCHOICE)); head = list_identifier; tail = list_identifier; //Create first item of the list and assign properties to it. list_identifier->backcolor0 = bcolor0; list_identifier->backcolor1 = bcolor1; list_identifier->forecolor0 = fcolor0; list_identifier->forecolor1 = fcolor1; list_identifier->wherex = x; list_identifier->wherey = y; list_identifier-> item = (char *)malloc(strlen(str) +1); strcpy(list_identifier->item, str); list_identifier->next = head; list_identifier->back = head; list_identifier->index = 0; } else { //Circular list structure newp = (LISTCHOICE *) malloc(sizeof(LISTCHOICE)); former = tail; //former pointer points to previous-last item former->next = newp; //previous item forward points to current item newp->back = former; //new item back points to previous-last item tail = newp; //the tail now 'becomes' (points to) the new item head->back = tail; // This way we close the circular list : First item back points to last item tail->next = head; // Last item next points to first item. //Creates subsequent items of the list and assign properties to it. newp->backcolor0 = bcolor0; newp->backcolor1 = bcolor1; newp->forecolor0 = fcolor0; newp->forecolor1 = fcolor1; newp->wherex = x; newp->wherey = y; newp->item = (char*) malloc(strlen(str) + 1); strcpy(newp->item, str); newp->index = former->index + 1; } } void free_list(LISTCHOICE *list_identifier) { /* removes list from memory */ LISTCHOICE *aux, *p; aux = tail; do { p=aux; aux = aux->back; free(p->item); //free off the string field free(p); //remove item } while (aux != head->back); } void move_up(LISTCHOICE *aux) { //Unmark Former Item gotoxy(aux->wherex,aux->wherey); outputcolor(aux->forecolor0,aux->backcolor0); printf("%s\n", aux->item); //Highlight current item *aux=*aux->back; //Go to previous item gotoxy(aux->wherex,aux->wherey); outputcolor(aux->forecolor1,aux->backcolor1); printf("%s\n", aux->item); } void move_down(LISTCHOICE *aux) { //Unmark Former Item gotoxy(aux->wherex,aux->wherey); outputcolor(aux->forecolor0,aux->backcolor0); printf("%s\n", aux->item); //Highlight current item *aux=*aux->next; //Go to next item gotoxy(aux->wherex,aux->wherey); outputcolor(aux->forecolor1,aux->backcolor1); printf("%s\n", aux->item); } void display_list() { /* Displays the items contained in the list with the properties specified in init_list. until the auxiliary pointer reaches the first item again First item is equal to tail->next. */ LISTCHOICE *aux; aux = head; do { gotoxy(aux->wherex,aux->wherey); outputcolor(aux->forecolor0,aux->backcolor0); printf("%s\n", aux->item); aux = aux->next; } while (aux != tail->next); } void start_vmenu(LISTCHOICE *list_data) { /* Starts the selection menu */ char ch; LISTCHOICE aux; display_list(); //display whole list //Highlight first item on the list aux=*tail; //Auxiliary variable points to last item move_down(&aux); //Move down to point to highlight first item. ch=0; // reset and initialise ch value while (ch != 10) // enter key { ch=getch(); if (ch=='\033') // escape key { getch(); // read key again for arrow key combinations switch(getch()) { case 'A': // escape key + A => arrow key up move_up(&aux); break; case 'B': // escape key + B => arrow key down move_down(&aux); break; } } } if (ch==10) // enter key { //Pass data of last item by value. *list_data = aux; } } int main_screen() { //Draws the main screen int i,j; //Draw the main screen rows=0; columns=0; screencol(B_BLUE); gotoxy(1,1); outputcolor(0,F_WHITE); //Save previous values old_rows = rows; old_columns = columns; get_terminal_dimensions(&rows,&columns); if (rows==0) rows=25; //just in case it can't find the terminal dimensions if (columns==0) columns=80; //Draw upper and lower bars outputcolor(F_WHITE,B_CYAN); for (i=0;i<=columns;i++) { gotoxy(i,1); printf(" "); } outputcolor(F_WHITE,B_WHITE); for (i=0;i<=columns;i++) { gotoxy(i,rows); printf(" "); } outputcolor(F_BLACK,B_CYAN); gotoxy(1,1); printf(" File Options Help"); outputcolor(FH_WHITE,B_BLUE); gotoxy(2,3); printf("Selection Menu"); gotoxy(2,4); printf("=============="); gotoxy(columns-6,1); outputcolor(FH_YELLOW,B_CYAN); printf("%d:%d",columns,rows); outputcolor(F_BLACK,B_WHITE); gotoxy(1,rows); printf("- Coded by Velorek"); } int main() { LISTCHOICE data; screencol(FH_BLUE); main_screen(); add_item(mylist,"Option 1",3,6,B_BLUE,FH_WHITE,B_RED,F_WHITE); add_item(mylist,"Option 2",3,7,B_BLUE,FH_WHITE,B_RED,F_WHITE); add_item(mylist,"Option 3",3,8,B_BLUE,FH_WHITE,B_RED,F_WHITE); add_item(mylist,"Option 4",3,9,B_BLUE,FH_WHITE,B_RED,F_WHITE); add_item(mylist,"Option 5",3,10,B_BLUE,FH_WHITE,B_RED,F_WHITE); add_item(mylist,"Exit",3,11,B_BLUE,FH_WHITE,B_GREEN,F_WHITE); outputcolor(F_BLUE,B_BLACK); do { start_vmenu(&data); gotoxy(20,18); printf("You have selected: %i:%s\n",data.index+1,data.item); } while (strcmp(data.item,"Exit") != 0); free_list(mylist); screencol(B_BLACK); printf("\n"); return 0; }

 Display:

We Love Colors - ANSI Functions II in C

You have several options to give your program a more attractive look in text-mode. Ncurses,for one, in Linux is an excellent choice. But if you want to keep it simple and do things fast, you can resort to using ANSI escape sequences. They work like a charm on Linux terminals. Unfortunately, its support was removed from Windows terminals. Although I hear Windows 10 has brought back support to these sequences. Alternatively, check Ansicon for windows support. 

From Wikipedia:

In C:

int gotoxy(int x,int y)
//Sets the cursor at the desired position.
{
  printf("%c[%d;%df",0x1B,y,x);
  return 0;
}

int outputcolor(int foreground, int background)
//Changes format foreground and background colors of display.
{
  printf("%c[%d;%dm", 0x1b,foreground,background);
  return 0;
}

int screencol(int x)
// Changes color of the entire screen.
{
  gotoxy(0,0);
  outputcolor(0,x);
  printf("%c[2J", 0x1b);
  outputcolor(0,0);
  return 0;
}