HTTP Status Codes
| Syntax / Command | Description |
|---|---|
200 | OK - Success |
201 | Created - Resource created |
204 | No Content - Success, no body |
400 | Bad Request - Invalid request |
401 | Unauthorized - Authentication required |
403 | Forbidden - No permission |
404 | Not Found - Resource missing |
422 | Unprocessable Entity - Validation error |
500 | Internal Server Error - Server failure |
502 | Bad Gateway - Gateway error |
503 | Service Unavailable - Temporarily down |
Git Commands
| Syntax / Command | Description |
|---|---|
git init | Initialize a repository |
git add . | Stage all changes |
git commit -m "message" | Commit changes |
git push | Push to remote |
git pull | Pull from remote |
git status | Check working tree status |
git log --oneline | Show concise history |
git checkout -b branch | Create and switch to branch |
git stash | Stash changes temporarily |
git stash pop | Restore stashed changes |
git restore file | Discard uncommitted changes |
Regex Patterns
| Syntax / Command | Description |
|---|---|
. | Any single character |
\d | Digit (0-9) |
\w | Word character (alphanumeric + _) |
\s | Whitespace (space, tab, etc.) |
\D | Non-digit |
\W | Non-word character |
\S | Non-whitespace |
\d+ | One or more digits |
\d* | Zero or more digits |
[abc] | a, b, or c |
^ | Start of line |
$ | End of line |
JSON Rules
| Syntax / Command | Description |
|---|---|
Keys must be double-quoted | Single quotes are not valid |
No trailing comma | No comma after the last element |
No comments | // and /* */ are not allowed |
null (lowercase) | Null or NULL are invalid |
Numbers need no quotes | 123 differs from the string "123" |
Markdown Syntax
| Syntax / Command | Description |
|---|---|
# Heading 1 | h1 |
## Heading 2 | h2 |
**bold** | Bold |
*italic* | Italic |
`code` | Inline code |
[text](URL) | Link |
 | Image |
- item | Unordered list item |
1. item | Ordered list item |
> quote | Blockquote |
| A | B | | Table |