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316
docs/resources/programming/c.md
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316
docs/resources/programming/c.md
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# C Programming Language Cheatsheet
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## Table of Contents
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- [Basic Structure](#basic-structure)
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- [Variables and Data Types](#variables-and-data-types)
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- [Memory Management](#memory-management)
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- [Binary Operators](#binary-operators)
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||||
- [Assignment Shortcuts](#assignment-shortcuts)
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- [Standard Input/Output Functions](#standard-inputoutput-functions)
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- [Standard Library Functions](#standard-library-functions)
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- [Best Practices](#best-practices)
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- [Advanced Topics](#advanced-topics)
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|
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## Basic Structure
|
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|
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### Program Template
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```c
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/* comment to describe the program */
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#include <stdio.h>
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/* definitions */
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int main(int argc, char **argv) {
|
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/* variable declarations */
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/* program statements */
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}
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```
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### Naming Conventions
|
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Variable names must follow these rules:
|
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- Can contain uppercase letters (A to Z)
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- Can contain lowercase letters (a to z)
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- Can contain numbers (0 to 9)
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- Can contain underscores (_)
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- Cannot start with a number
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- Are case-sensitive
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## Variables and Data Types
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### Basic Data Types
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| Data Type | Description | Example Usage |
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|-----------|-------------|---------------|
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| int | Integer values | `int count = -1;` |
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| char | Character values | `char letter = 'A';` |
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| float | Floating point numbers | `float pi = 3.141f;` |
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| double | Double precision numbers | `double precise_pi = 3.14159265359;` |
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### Variable Declaration Examples
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```c
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int age;
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char initial;
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float temperature;
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double precise_measurement;
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int *pointer_to_int;
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char string_array[50];
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```
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|
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## Memory Management
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|
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### Dynamic Memory Allocation
|
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```c
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// Allocating memory
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int *array = (int *) malloc(sizeof(int) * 10);
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if (array == NULL) {
|
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/* handle allocation failure */
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}
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|
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// Resizing memory
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int *newarray = (int *) realloc(array, sizeof(int) * 20);
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if (newarray == NULL) {
|
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/* handle reallocation failure */
|
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}
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array = newarray;
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|
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// Freeing memory
|
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free(array);
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```
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|
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### Memory Management Best Practices
|
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1. Always check for NULL after malloc/realloc
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2. Always free allocated memory when no longer needed
|
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3. Never free memory more than once
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4. Update pointers after reallocation
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5. Initialize pointers to NULL when declaring
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|
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## Binary Operators
|
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|
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### Bitwise Operations
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| Operator | Description | Example |
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|----------|-------------|----------|
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| a & b | Bitwise AND | `result = 5 & 3;` |
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| a \| b | Bitwise OR | `result = 5 \| 3;` |
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| a ^ b | Bitwise XOR | `result = 5 ^ 3;` |
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| a << n | Left shift | `result = 5 << 2;` |
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| a >> n | Right shift | `result = 5 >> 2;` |
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|
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## Assignment Shortcuts
|
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|
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### Compound Assignment Operators
|
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| Operator | Equivalent | Example |
|
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|----------|------------|---------|
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| += | a = a + b | `a += b;` |
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| -= | a = a - b | `a -= b;` |
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| *= | a = a * b | `a *= b;` |
|
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| /= | a = a / b | `a /= b;` |
|
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| %= | a = a % b | `a %= b;` |
|
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|
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## Standard Input/Output Functions
|
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|
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### Standard Streams
|
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| Stream | Description | Usage |
|
||||
|--------|-------------|-------|
|
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| stdin | Standard input | Reading user input |
|
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| stdout | Standard output | Normal program output |
|
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| stderr | Standard error | Error messages |
|
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|
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### File Operations
|
||||
```c
|
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FILE *fopen(char *filename, char *mode);
|
||||
size_t fread(void *ptr, size_t size, size_t nitems, FILE *stream);
|
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int fclose(FILE *stream);
|
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```
|
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|
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### Input/Output Functions
|
||||
```c
|
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// String output
|
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int puts(char *string);
|
||||
int printf(char *format, ...);
|
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int fprintf(FILE *stream, char *format);
|
||||
int sprintf(char *string, char *format);
|
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|
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// Character input/output
|
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int getc(FILE *stream);
|
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int putc(int ch, FILE *stream);
|
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int getchar(void);
|
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int putchar(int ch);
|
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```
|
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|
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## Standard Library Functions
|
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|
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### Memory Management Functions
|
||||
```c
|
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void *malloc(size_t size);
|
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void *realloc(void *ptr, size_t newsize);
|
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void free(void *ptr);
|
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```
|
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|
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### Sorting and Searching
|
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```c
|
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void qsort(void *array, size_t nitems, size_t size,
|
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int (*compar)(void *a, void *b));
|
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void *bsearch(void *key, void *array, size_t nitems,
|
||||
size_t size, int (*compar)(void *a, void *b));
|
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```
|
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|
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### Random Number Generation
|
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```c
|
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void srand(unsigned int seed);
|
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int rand(void);
|
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```
|
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|
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## Best Practices
|
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|
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### Memory Management Guidelines
|
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1. Always initialize variables before use
|
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2. Check return values from memory allocation functions
|
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3. Free dynamically allocated memory
|
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4. Avoid memory leaks
|
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5. Use appropriate data types for variables
|
||||
|
||||
### Code Organization
|
||||
1. Include necessary header files at the start
|
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2. Define constants and macros after headers
|
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3. Declare global variables (if needed) after definitions
|
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4. Define functions before use or provide prototypes
|
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5. Use meaningful variable and function names
|
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|
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### Error Handling
|
||||
1. Always check return values of system calls
|
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2. Use stderr for error messages
|
||||
3. Implement proper error recovery mechanisms
|
||||
4. Clean up resources in error conditions
|
||||
5. Use appropriate error codes
|
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|
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## Advanced Topics
|
||||
|
||||
### Function Pointers
|
||||
```c
|
||||
// Declaration of a function pointer
|
||||
int (*operation)(int, int);
|
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|
||||
// Example usage
|
||||
int add(int a, int b) {
|
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return a + b;
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}
|
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|
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operation = &add;
|
||||
int result = (*operation)(5, 3);
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```
|
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|
||||
### Structures and Unions
|
||||
```c
|
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struct Point {
|
||||
int x;
|
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int y;
|
||||
};
|
||||
|
||||
union Data {
|
||||
int i;
|
||||
float f;
|
||||
char str[20];
|
||||
};
|
||||
```
|
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|
||||
### Preprocessor Directives
|
||||
```c
|
||||
#define MAX_SIZE 100
|
||||
#define SQUARE(x) ((x) * (x))
|
||||
#ifdef DEBUG
|
||||
// Debug code
|
||||
#endif
|
||||
#ifndef HEADER_H
|
||||
#define HEADER_H
|
||||
// Header content
|
||||
#endif
|
||||
```
|
||||
|
||||
### Type Definitions
|
||||
```c
|
||||
typedef unsigned long ulong;
|
||||
typedef struct Point Point;
|
||||
typedef void (*CallbackFunc)(void *data);
|
||||
```
|
||||
|
||||
### Bit Fields
|
||||
```c
|
||||
struct Flags {
|
||||
unsigned int is_active : 1;
|
||||
unsigned int is_urgent : 1;
|
||||
unsigned int priority : 3;
|
||||
};
|
||||
```
|
||||
|
||||
## Common Programming Patterns
|
||||
|
||||
### Buffer Management
|
||||
```c
|
||||
#define BUFFER_SIZE 1024
|
||||
|
||||
char buffer[BUFFER_SIZE];
|
||||
size_t bytes_read;
|
||||
|
||||
// Safe reading
|
||||
if ((bytes_read = fread(buffer, 1, BUFFER_SIZE - 1, file)) > 0) {
|
||||
buffer[bytes_read] = '\0';
|
||||
}
|
||||
```
|
||||
|
||||
### String Manipulation
|
||||
```c
|
||||
// String copy with bounds checking
|
||||
char dest[50];
|
||||
const char *src = "Hello, World!";
|
||||
strncpy(dest, src, sizeof(dest) - 1);
|
||||
dest[sizeof(dest) - 1] = '\0';
|
||||
```
|
||||
|
||||
### Command Line Arguments
|
||||
```c
|
||||
int main(int argc, char **argv) {
|
||||
for (int i = 1; i < argc; i++) {
|
||||
printf("Argument %d: %s\n", i, argv[i]);
|
||||
}
|
||||
return 0;
|
||||
}
|
||||
```
|
||||
|
||||
## Debugging Tips
|
||||
|
||||
### Common Debugging Techniques
|
||||
1. Use printf debugging
|
||||
2. Check return values
|
||||
3. Validate pointer operations
|
||||
4. Monitor memory usage
|
||||
5. Use assert statements
|
||||
|
||||
### Assert Usage
|
||||
```c
|
||||
#include <assert.h>
|
||||
|
||||
void process_data(int *data, size_t size) {
|
||||
assert(data != NULL);
|
||||
assert(size > 0);
|
||||
// Process data
|
||||
}
|
||||
```
|
||||
|
||||
## Performance Optimization
|
||||
|
||||
### Optimization Techniques
|
||||
1. Use appropriate data structures
|
||||
2. Minimize memory allocation
|
||||
3. Optimize loops
|
||||
4. Use bitwise operations when applicable
|
||||
5. Consider cache efficiency
|
||||
|
||||
### Example Optimizations
|
||||
```c
|
||||
// Optimized loop
|
||||
for (int i = 0; i < size; i++) {
|
||||
// Cache the value to avoid multiple array accesses
|
||||
int temp = array[i];
|
||||
if (temp > max) {
|
||||
max = temp;
|
||||
}
|
||||
}
|
||||
```
|
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173
docs/resources/programming/emacs.md
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173
docs/resources/programming/emacs.md
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@@ -0,0 +1,173 @@
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# GNU Emacs Cheatsheet
|
||||
|
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## Emacs Commands Relation Diagram
|
||||
[](https://mermaid.live/edit#pako:eNqNll2PmzgUQP-KRdWqK000JSRth4eVWqZVqi2UbdIirdMHB0xiDV_CMElU9b_vvTZJKcWi88AE-_gaH-41_m7FZcIt19rXrDqQj5-3BYG_p0-Jz0RBPNbwfVkLLslRNAeybs6ZKPYaijMm5T1PSaypM0lFlrlPuJ0uU34jm7p84O6TF_by1d2uu50dRdIc3Hl1GsSQ7W4QJnX4Ml1ewyyYvXgd_xrG_i1MXOY5K5JLCDt9ze-uIRzn5Z3NDSH09V3OYvlcXYmnY8m_XNe9PFufBUnvRcbJp4rXrBFlIcm63SmRGpDdncIkHcDfNIR_73XfZcJvMGHPR4-zqTc7EW-WuhioQLBbcQ-ad5B0yZo98nHI6aCjhsgbOc4tOu7BJV5WSkO0ZUfFLvm3Fc0o1MPJbPY3LIY8g4fFi4OXBV6WmuKXgVfTG35q_sA0YnTA9kRvdN-k6I1N1zzjMY53UWXF4vGlb-b0nkvFIrgfhxz6pUhKBG4n3GyUmw262aCbjWMyErBHsVcrNMkAgv6kehoC6pePPOfFH6gIbPpRFFziw1e33mw86QJIugOrFbUDKh2nHBqVdQKUD5RvohZqRthsWN3cvisSDMogKJ9wFyh3AboL0F2AeRUsTAK9TFS7ktWJyR8C9Er1_HnUK6szBA-ZbLhRnWfTTc0SgfZZZsbA3Zc3xIeN2Mj0aMhNr1XJdhz14UFK4uOhZBPhUPXkGOQ8IdXzr_OdxqP5l_mg_g1Eb77HqfnUS_TwJXrzvkvdrirDU6XhXWpDS9T9vur3Vb9vrJ1IQDkejbsIdNML8oy8bdOU1_1tJOp6p6sngo2kykRDvuLandG1R_OOWSEzH2ccGpREYQjZ49CCfuY5VDYiL8aRJf3UHHjdGUCwnHghkRIbodcItUZYVRHu1pFxtw5Z_MD2HA4RBfxTG41BNZL0d7wnO7x2T9oOca-SDWb-iWTwa1bpoeMft1Dt3XEtdlwPSbq7y7DxUQ79UMiGwQFDDerYmdCNEzZDZTNEmyHaDI05uuJZRdZnKJvcJA8R2uN61la6fVLZyqb_8LOKhMlwIA-jC1jN6VvIGDj7SY3tJta5Uutc4TpXc9MS1RkzLotCf2ll7wymjwh4bho24hd82AZfuWET7tvDNkj6YRPm1rANZVg3Vs7rnIkEDsffkdhaUDg531ou_Ex4ytqs2Vrb4gegrG3K9bmILbepW35j1WW7P1xu2ioB7feCwUvLLTdlmYTWihX_lWWuoR__A-hhZFE)
|
||||
|
||||
## Key Notation
|
||||
- `C-` means hold the Control key
|
||||
- `M-` means hold the Alt key (Meta) or press and release Escape
|
||||
- `C-x` means press Control and 'x' together
|
||||
- `M-x` means press Alt and 'x' together or press Escape then 'x'
|
||||
|
||||
## File Operations
|
||||
| Command | Description |
|
||||
|---------|-------------|
|
||||
| `C-x C-f` | Open a file |
|
||||
| `C-x C-s` | Save current file |
|
||||
| `C-x C-w` | Save as... |
|
||||
| `C-x C-k` | Close file |
|
||||
| `C-x C-c` | Quit Emacs |
|
||||
|
||||
## Text Selection
|
||||
| Command | Description |
|
||||
|---------|-------------|
|
||||
| `C-<space>` or `C-@` | Start selection |
|
||||
| `C-g` | Deselect |
|
||||
|
||||
## Navigation Commands
|
||||
### Line Navigation
|
||||
| Command | Description |
|
||||
|---------|-------------|
|
||||
| `C-p` | Move to previous line |
|
||||
| `C-n` | Move to next line |
|
||||
|
||||
### Character Navigation
|
||||
| Command | Description |
|
||||
|---------|-------------|
|
||||
| `C-b` | Move back one character |
|
||||
| `C-f` | Move forward one character |
|
||||
|
||||
### Word Navigation
|
||||
| Command | Description |
|
||||
|---------|-------------|
|
||||
| `M-b` | Move back one word |
|
||||
| `M-f` | Move forward one word |
|
||||
|
||||
### Line Boundaries
|
||||
| Command | Description |
|
||||
|---------|-------------|
|
||||
| `C-a` | Go to start of line |
|
||||
| `C-e` | Go to end of line |
|
||||
|
||||
## Copy & Paste Operations
|
||||
### Traditional Emacs Style
|
||||
| Command | Description |
|
||||
|---------|-------------|
|
||||
| `C-w` | Cut (Kill) |
|
||||
| `M-w` | Copy |
|
||||
| `C-y` | Paste (Yank) |
|
||||
| `C-k` | Cut line after cursor |
|
||||
| `M-d` | Cut word after cursor |
|
||||
|
||||
### Modern Style (CUA Mode)
|
||||
| Command | Description |
|
||||
|---------|-------------|
|
||||
| `M-x cua-mode` | Activate modern copy & paste |
|
||||
| `C-x` | Cut |
|
||||
| `C-c` | Copy |
|
||||
| `C-v` | Paste |
|
||||
|
||||
## Undo Operations
|
||||
| Command | Description |
|
||||
|---------|-------------|
|
||||
| `C-/` or `C-x u` | Undo last operation |
|
||||
|
||||
## Windows, Frames, and Buffers
|
||||
### Split Operations
|
||||
| Command | Description |
|
||||
|---------|-------------|
|
||||
| `C-3` | Split window vertically |
|
||||
| `C-2` | Split window horizontally |
|
||||
| `C-1` | Remove all splits (single window) |
|
||||
| `C-0` | Remove current window |
|
||||
|
||||
### Buffer Management
|
||||
| Command | Description |
|
||||
|---------|-------------|
|
||||
| `C-x <arrow>` | Cycle through active buffers |
|
||||
| `C-o` | Visit other split window |
|
||||
|
||||
### Frame Management
|
||||
| Command | Description |
|
||||
|---------|-------------|
|
||||
| `C-x 52` | Open a new frame |
|
||||
|
||||
## Emergency Commands
|
||||
| Command | Description |
|
||||
|---------|-------------|
|
||||
| `C-g` | Cancel current operation/command |
|
||||
|
||||
## Help System
|
||||
| Command | Description |
|
||||
|---------|-------------|
|
||||
| `C-h k <key combo>` | Show key combination binding |
|
||||
| `C-h b` | Display all key bindings |
|
||||
|
||||
## Package Management
|
||||
| Command | Description |
|
||||
|---------|-------------|
|
||||
| `M-x list-packages` | List all available packages |
|
||||
| `M-x describe-package` | Describe package at cursor |
|
||||
| `M-x package-menu-mark-install` | Mark package for installation |
|
||||
| `M-x package-install-selected-packages` | Install marked packages |
|
||||
|
||||
## Important Concepts
|
||||
1. **Buffer**: Holds a process or file content
|
||||
2. **Window**: Your view of a buffer
|
||||
3. **Frame**: The desktop window containing Emacs
|
||||
|
||||
## Additional Navigation Methods
|
||||
- Use arrow keys for cursor movement if available
|
||||
- Use mouse to click and drag for text selection
|
||||
|
||||
## Tips for New Users
|
||||
1. Start with basic file operations and navigation
|
||||
2. Learn the help system commands early
|
||||
3. Consider using CUA mode if coming from other editors
|
||||
4. Practice emergency cancel (`C-g`) for when things go wrong
|
||||
5. Use package management to extend functionality
|
||||
|
||||
## Customization Basics
|
||||
```elisp
|
||||
;; Add to your .emacs file or init.el
|
||||
;; Enable CUA mode for familiar copy-paste
|
||||
(cua-mode t)
|
||||
|
||||
;; Enable line numbers
|
||||
(global-display-line-numbers-mode)
|
||||
|
||||
;; Enable syntax highlighting
|
||||
(global-font-lock-mode t)
|
||||
```
|
||||
|
||||
## Common Workflows
|
||||
|
||||
### File Management Workflow
|
||||
1. Open Emacs
|
||||
2. Use `C-x C-f` to find file
|
||||
3. Edit content
|
||||
4. Save with `C-x C-s`
|
||||
5. Close with `C-x C-k` or quit Emacs with `C-x C-c`
|
||||
|
||||
### Text Editing Workflow
|
||||
1. Navigate to location
|
||||
2. Start selection with `C-<space>`
|
||||
3. Move cursor to select text
|
||||
4. Cut/copy as needed
|
||||
5. Navigate to new location
|
||||
6. Paste content
|
||||
|
||||
### Window Management Workflow
|
||||
1. Split window as needed (`C-2` or `C-3`)
|
||||
2. Open different files in splits
|
||||
3. Use `C-o` to switch between splits
|
||||
4. Close splits when done (`C-0` or `C-1`)
|
||||
|
||||
## Best Practices
|
||||
1. Learn the help system first
|
||||
2. Practice navigation commands
|
||||
3. Use package management for extensions
|
||||
4. Learn buffer management
|
||||
5. Master window splitting
|
||||
6. Understand the difference between kill/yank and modern copy/paste
|
||||
7. Keep emergency commands in mind
|
||||
Reference in New Issue
Block a user