SimpleLine

A lightweight, header-only C library providing interactive line editing on Linux, inspired by isocline and linenoise.

Features

• Interactive line editing on Linux terminals with inline cursor movement
• UTF-8 & CJK support — full Unicode width-aware rendering
• Line editing keys — Left/Right, Home/End, Backspace/Delete
• Word movement — Ctrl+Left, Ctrl+Right
• Word deletion — Ctrl+Backspace (delete word left), Ctrl+Delete (delete word right)
• History — Up/Down arrows, 50-entry circular buffer, deduplication
• Tab — inserts literal tab at line start (Python-style indentation)
• Ctrl+C abort, Ctrl+D EOF on empty line, Ctrl+L clear screen
• Non-interactive fallback — automatically handles piped input
• History persistence — sl_load_history() / sl_save_history() APIs
• Header-only — drop simpleline.h into your project, no linker flags needed
• Windows — falls back to non-interactive input (conhost.exe built-in readline is superior)

Quick Start

# Build with xmake
xmake

# Run the demo REPL
xmake run

# Run tests
xmake run_test

Or build with any C compiler:

cc -o simpleline src/main.c

API Reference

// Read a line of input (interactive on TTY, simple otherwise)
sl_result_t sl_input(char* prompt);

// Free the result buffer
void sl_free_result(sl_result_t* result);

// Free all history entries
void sl_free_history(void);

// Load history from a file
bool sl_load_history(const char* filename);

// Save history to a file
bool sl_save_history(const char* filename);

sl_result_t

typedef struct {
    char*          buf;       // The input line (null-terminated)
    unsigned long long len;   // Length of the line
    unsigned long long capacity; // Allocated capacity
    sl_exception_t exception; // SL_OK, SL_EXCEPTION_EOF, or SL_EXCEPTION_OUT_OF_MEMORY
} sl_result_t;

When buf is NULL, check exception to distinguish EOF from out-of-memory.

Key Bindings

Key	Action
Left / Right	Move cursor one character
Ctrl+Left / Ctrl+Right	Move one word
Home (CSI/SS3/vt100)	Move to beginning of line
End (CSI/SS3/vt100)	Move to end of line
Backspace	Delete character before cursor
Delete	Delete character at cursor
Ctrl+Backspace (^W)	Delete word before cursor
Ctrl+Delete	Delete word after cursor
Up / Down	Navigate history
Tab	Insert tab (line-start only)
Enter	Submit line
Ctrl+C	Abort (returns EOF)
Ctrl+D	EOF on empty line
Ctrl+L	Clear screen

Typical Usage Pattern

#include "simpleline.h"

int main(void) {
    sl_load_history("history.txt");

    while (1) {
        sl_result_t r = sl_input("$ ");
        if (!r.buf) break;  // EOF or error
        process(r.buf);
        sl_free_result(&r);
    }

    sl_save_history("history.txt");
    sl_free_history();
    return 0;
}

Project Structure

├── src/
│   ├── simpleline.h    # Header-only library (all logic)
│   └── main.c          # Demo REPL entry point
├── test/
│   └── test_basic.py   # 25 PTY-based integration tests
├── xmake.lua           # Build configuration
└── README.md

License

MIT