Implementing a Simple Text Editor in C Language

In this article, we will learn how to implement a simple text editor using the C language. This text editor will be able to perform basic file operations such as opening, reading, writing, and saving files. Our goal is to help beginner users understand how to handle file input and output in C, as well as to establish basic data structures to store and manipulate text.

1. Project Overview

We will build a command-line interface text editor with the following features:

• Create a new file
• Open an existing file
• Edit content (add, delete)
• Save modified content
• Display current content

2. Necessary Preparations

Before we start programming, please ensure that you have a C compiler installed on your system, with GCC being the recommended option. In a Linux or Mac environment, you can run <span>gcc --version</span> to confirm if it is installed. On Windows, it is advisable to install MinGW or other tools that support C language development as needed.

3. Writing the Code

Next, let’s code this simple text editor step by step.

3.1 File Inclusions and Macro Definitions

First, we need to include the necessary header files and define some constants for the string buffer:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX_BUFFER_SIZE 1024

3.2 Text Structure

Then, to store our text data, we create a structure <span>TextEditor</span> to hold the information of the current document.

typedef struct {
    char **lines;
    int line_count;
    int max_lines;
} TextEditor;

3.3 Function Declarations

Next, we will declare some functions to handle different functionalities:

void init_editor(TextEditor *editor);
void open_file(TextEditor *editor, const char *filename);
void save_file(TextEditor *editor, const char *filename);
void display_content(TextEditor *editor);
void edit_content(TextEditor *editor, const char *new_line);

3.4 Initializing the Document

Here is the function to initialize <span>TextEditor</span>:

void init_editor(TextEditor *editor) {
    editor->line_count = 0;
    editor->max_lines = MAX_BUFFER_SIZE; // Set maximum number of lines to BUFFER_SIZE
    editor->lines = (char **)malloc(editor->max_lines * sizeof(char*));
    for (int i = 0; i < editor->max_lines; i++) {
        editor->lines[i] = (char *)malloc(MAX_BUFFER_SIZE); // Allocate memory for each line
    }
}

3.5 Opening an Existing File and Reading

Update the following function to open and read an existing document from the specified path:

void open_file(TextEditor *editor, const char *filename) {
    FILE* file = fopen(filename, "r");
    if (!file) {
        perror("Unable to open file");
        return;
    }
    while (fgets(editor->lines[editor->line_count], MAX_BUFFER_SIZE, file)) {
        editor->line_count++;
        if (editor->line_count >= editor->max_lines) break; // Exit if maximum line count is reached
    }
    fclose(file); // Close the file after completion
}

3.6 Saving to a New Document

This function saves the current content to the specified path:

void save_file(TextEditor *editor, const char* filename) {
    FILE* file = fopen(filename, "w");
    if(!file){
        perror("Unable to save to this file");
        return;
    }
    for(int i=0; i < editor->line_count; i++) {
        fprintf(file, "%s", editor->lines[i]);
    }
    fclose(file); // Close the file after completion
}

3.7 Displaying Content

Display all the data being edited so that the user is aware of the current situation:

void display_content(TextEditor* editor) {
    for(int i=0; i < editor->line_count; i++)
        printf("%d: %s", i+1, editor->lines[i]);
}

Finally, Integrating These Parts

Now, integrate all functionalities into the main function to provide user interaction:

int main() {
    TextEditor my_editor;
    init_editor(&my_editor);
    int choice;
    do {
        printf("\nSelect operation:\n");
        printf("1 - Open a new arrangement:\n");
        printf("2 - Simplify multiple points:\n");
        printf("3 - Cursor complexity:\n");
        // Add logic for user choice
        switch(choice) {
            case '1':
                // Call function to open file
                break;
            case '2':
                display_content(&my_editor);
                break;
            default:
                puts("Error: Invalid choice");
                continue;
        }
    } while(choice != exit);
    free(my_editor.lines);
}

Finally, do not forget to free the dynamically allocated memory to prevent memory leaks.

Conclusion

This article introduced how to create a simple text editor with minimal code while having basic capabilities. For example, it can be easily extended by combining additional features, and this program can serve as a foundation for more complex applications.

I hope this helps you understand string handling and dynamic memory allocation in C, as well as building applications.