Start code for the I/O project chapter

src/SUMMARY.md

@@ -55,7 +55,7 @@
     - [Running tests](ch11-02-running-tests.md)
     - [Test Organization](ch11-03-test-organization.md)
 
-- [I/O]()
+- [An I/O Project](ch12-00-an-io-project.md)
     - [`Read` & `Write`]()
     - [`std::fs`]()
     - [`std::path`]()

src/ch12-00-an-io-project.md

@@ -0,0 +1,35 @@
+# An I/O Project
+
+`cargo new --bin greprs`
+
+Project requirements:
+
+- Take a search string and a filename as command line arguments
+- Read the file
+- Find lines in the file that contain the search string
+- Print out those lines
+
+In order to do a good job, we will:
+
+- Organize code (using what we learned in modules, ch 7)
+- Use strings (collections, ch 8)
+- Handle errors (ch 9)
+- Have tests (ch 11)
+
+Generics/traits/lifetimes?
+
+## Command line arguments
+
+* Use `std::env::args()`
+
+Filename: src/main.rs
+
+```rust
+use std::env;
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+    println!("{:?}", args);
+}
+```
+