chapter-2

Author: rakurame96

cli-book/Cargo.toml

@@ -2,5 +2,6 @@
 resolver = "2"
 
 members = [ 
-    "cli-rs",
+    "cli-rs", 
+    "echor",
 ]

cli-book/echor/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "echor"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+clap = "4.5.23"

cli-book/echor/src/main.rs

@@ -0,0 +1,40 @@
+use clap::{Arg, ArgAction, Command};
+
+/*
+// default will be "first value to be the path of the program itself"
+// and any arguments passed to the program while calling the cargo run
+// ex: cargo run a b c
+Args {
+    inner: ["E:\\Learning-to-code\\rust-workspace\\cli-book\\target\\debug\\echor.exe", "a", "b", "c"]
+    }
+*/
+fn main() {
+    // println!("{:?}", std::env::args());
+    let matches = Command::new("echor")
+        .version("0.1.0")
+        .author("Rakuram <[email protected]>")
+        .about("Rust Echo Command")
+        .help_template(
+            "{name} {version} \n\
+             {author} \n\
+             {about} \n\n\
+             USAGE: \n    {usage}\n\n\
+             {all-args}",
+        )
+        .arg(
+            Arg::new("text")
+                .value_name("TEXT")
+                .help("Input Text")
+                .required(true)
+                .num_args(1..),
+        )
+        .arg(
+            Arg::new("omit_newline")
+                .short('n')
+                .help("Do not print the newline")
+                .action(ArgAction::SetTrue),
+        )
+        .get_matches();
+
+    println!("{:#?}", matches);
+}

inpyjama-30-days-of-rust/README.md

@@ -163,6 +163,22 @@ cargo run --quiet --bin true
 cargo test -- --test-threads=1
 ```
 
+### Cargo Arguments
+- ```shell
+  # below command will result in error
+  cargo run -n Hello world
+  # below command will execute without any error
+  cargo run -- -n Hello world
+  ```
+- Without `--`: Cargo tries to interpret the arguments as options for itself. Since `-n` is not a valid Cargo flag, it results in an error.
+- With `--`: The `--` tells Cargo, "Stop processing options for yourself; pass everything after this directly to the program."
+- **When to Use --?**
+    - Use `--` whenever you need to pass arguments to your Rust program that might be confused as flags for Cargo. For example:
+    - ```shell
+      cargo run -- -v
+      ```
+    - This passes `-v` to your program, not to Cargo. Without `--`, Cargo would interpret `-v` as a flag for itself (e.g., for verbose output).
+
 ### to install rust from rustup
 ```shell
 # installs nightly (unstable) version