Allow example CLI to read from stdin (#1536)

Author: mvzink

examples/cli.rs

@@ -17,9 +17,11 @@
 
 #![warn(clippy::all)]
 
-/// A small command-line app to run the parser.
-/// Run with `cargo run --example cli`
+//! A small command-line app to run the parser.
+//! Run with `cargo run --example cli`
+
 use std::fs;
+use std::io::{stdin, Read};
 
 use simple_logger::SimpleLogger;
 use sqlparser::dialect::*;
@@ -38,6 +40,9 @@ $ cargo run --example cli FILENAME.sql [--dialectname]
 To print the parse results as JSON:
 $ cargo run --feature json_example --example cli FILENAME.sql [--dialectname]
 
+To read from stdin instead of a file:
+$ cargo run --example cli - [--dialectname]
+
 "#,
     );
 
@@ -57,9 +62,18 @@ $ cargo run --feature json_example --example cli FILENAME.sql [--dialectname]
         s => panic!("Unexpected parameter: {s}"),
     };
 
-    println!("Parsing from file '{}' using {:?}", &filename, dialect);
-    let contents = fs::read_to_string(&filename)
-        .unwrap_or_else(|_| panic!("Unable to read the file {}", &filename));
+    let contents = if filename == "-" {
+        println!("Parsing from stdin using {:?}", dialect);
+        let mut buf = Vec::new();
+        stdin()
+            .read_to_end(&mut buf)
+            .expect("failed to read from stdin");
+        String::from_utf8(buf).expect("stdin content wasn't valid utf8")
+    } else {
+        println!("Parsing from file '{}' using {:?}", &filename, dialect);
+        fs::read_to_string(&filename)
+            .unwrap_or_else(|_| panic!("Unable to read the file {}", &filename))
+    };
     let without_bom = if contents.chars().next().unwrap() as u64 != 0xfeff {
         contents.as_str()
     } else {