diff --git a/Cargo.toml b/Cargo.toml
index 29331c3..6ebfe07 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -23,10 +23,12 @@ same-file = "1.0.6"
 unicode-width = "0.2.0"
 
 [dev-dependencies]
-pretty_assertions = "1.4.0"
 assert_cmd = "2.0.14"
+criterion = { version = "0.8.2", features = ["html_reports"] }
+pretty_assertions = "1.4.0"
 predicates = "3.1.0"
-tempfile = "3.10.1"
+rand = "0.10.0"
+tempfile = "3.26.0"
 
 [profile.release]
 lto = "thin"
@@ -40,3 +42,8 @@ panic = "abort"
 [profile.dist]
 inherits = "release"
 lto = "thin"
+
+[[bench]]
+name = "bench_cmp"
+path = "benches/benchmarks-criterion.rs"
+harness = false
diff --git a/benches/benchmarks-criterion.rs b/benches/benchmarks-criterion.rs
new file mode 100644
index 0000000..442b89a
--- /dev/null
+++ b/benches/benchmarks-criterion.rs
@@ -0,0 +1,284 @@
+/// Benchmarks, currently only for cmp
+///
+/// Provides some general functions, e.g. to create files to compare in different sizes.
+///
+/// use hyperfine to benchmark against cmp
+/// * hyperfine -i "target/release/diffutils cmp from_file_10000000.txt to_file_10000000.txt"  
+/// * hyperfine -i "cmp from_file_10000000.txt to_file_10000000.txt"  
+///
+/// The Rust version seems twice as slow.
+use criterion::{criterion_group, criterion_main, Criterion};
+// use std::env;
+// use std::hint::black_box;
+use rand::RngExt;
+use std::io::{BufWriter, Write};
+use std::path::Path;
+use std::process::Command;
+use std::{ffi::OsString, fs::File, time::Duration};
+
+const WARM_UP_TIME_MS: u64 = 500;
+#[allow(unused)]
+const MEASUREMENT_TIME_MS: u64 = 2000;
+
+// file lines and .txt will be added
+const FROM_FILE: &str = "from_file";
+const TO_FILE: &str = "to_file";
+
+criterion_group!(
+    benches,
+    bench_parser,
+    bench_cmp // , bench_diff
+);
+criterion_main!(benches);
+
+// All results are a few microseconds, so negligible.
+fn bench_parser(c: &mut Criterion) {
+    let mut group = c.benchmark_group("Bench parser");
+
+    group.warm_up_time(Duration::from_millis(WARM_UP_TIME_MS));
+    // group.measurement_time(Duration::from_millis(MEASUREMENT_TIME_MS));
+    // group.sample_size(10);
+
+    group.bench_function("Parse cmp", |b| {
+        b.iter(|| {
+            cmp_parse_only(
+                "cmd file_1.txt file_2.txt -bl --bytes=2048 --ignore-initial=100KiB:1MiB",
+            )
+        })
+    });
+
+    group.bench_function("Parse diff", |b| {
+        b.iter(|| diff_parse_only("diff file_1.txt file_2.txt"))
+    });
+    // group.bench_function("Parse error", |b| {
+    //     b.iter(|| parse_single_arg("cmd file_1.txt file_2.txt --something-unknown"))
+    // });
+    // group.bench_function("Parse help", |b| b.iter(|| parse_single_arg("cmd --help")));
+
+    group.finish();
+}
+
+// This is the interesting part.
+fn bench_cmp(c: &mut Criterion) {
+    let mut group = c.benchmark_group("Bench cmp");
+    // uses tmp
+    // let dir_path = tempfile::tempdir().unwrap().path();
+    // uses current directory, the generated files are kept
+    let dir_path = Path::new("");
+    // let curr = env::current_dir().unwrap();
+    // let dir_path = curr.as_path();
+    let num_lines = 100_000;
+    // The more differences, the faster cmp returns, as it stops after the first difference is found.
+    let num_differences = 1;
+
+    group.warm_up_time(Duration::from_millis(WARM_UP_TIME_MS));
+    // group.measurement_time(Duration::from_millis(MEASUREMENT_TIME_MS));
+    // group.sample_size(10);
+
+    let (from, to) =
+        generate_test_files(num_lines, 0, dir_path).expect("generate_test_files failed");
+    let cmd = format!("cmp {from} {to}");
+    let opts = str_to_args(&cmd).into_iter().peekable();
+    let params = diffutilslib::cmp::parse_params(opts).unwrap();
+
+    group.bench_function(format!("cmp files unchanged, lines: {num_lines}"), |b| {
+        b.iter(|| diffutilslib::cmp::cmp(&params).unwrap())
+    });
+
+    let (from, to) = generate_test_files(num_lines, num_differences, dir_path)
+        .expect("generate_test_files failed");
+    let cmd = format!("cmp {from} {to} -s");
+    let opts = str_to_args(&cmd).into_iter().peekable();
+    let params = diffutilslib::cmp::parse_params(opts).unwrap();
+
+    group.bench_function(format!("cmp files changed, lines: {num_lines}"), |b| {
+        b.iter(|| diffutilslib::cmp::cmp(&params).unwrap())
+    });
+
+    group.finish();
+
+    // Optional bench by executing the file as cmd
+    bench_binary_execution_cmp(c);
+}
+
+// // This is the interesting part.
+// fn bench_diff(c: &mut Criterion) {
+//     let mut group = c.benchmark_group("Bench cmp");
+//     // uses tmp
+//     // let dir_path = tempfile::tempdir().unwrap().path();
+//     // uses current directory, the generated files are kept
+//     let dir_path = Path::new("");
+//     // let curr = env::current_dir().unwrap();
+//     // let dir_path = curr.as_path();
+//     let num_lines = 100_000;
+//     // The more differences, the faster cmp returns, as it stops after the first difference is found.
+//     let num_differences = 1;
+//
+//     group.warm_up_time(Duration::from_millis(WARM_UP_TIME_MS));
+//     // group.measurement_time(Duration::from_millis(MEASUREMENT_TIME_MS));
+//     // group.sample_size(10);
+//
+//     let (from, to) =
+//         generate_test_files(num_lines, 0, dir_path).expect("generate_test_files failed");
+//     let cmd = format!("diff {from} {to}");
+//     let opts = str_to_args(&cmd).into_iter().peekable();
+//     let params = diffutilslib::params::parse_params(opts).unwrap();
+//
+//     // TODO need function because main cannot be called.
+//     group.bench_function(format!("diff files unchanged, lines: {num_lines}"), |b| {
+//         b.iter(|| diffutilslib::<diff>::cmp(&params).unwrap())
+//     });
+//
+//     let (from, to) = generate_test_files(num_lines, num_differences, dir_path)
+//         .expect("generate_test_files failed");
+//     let cmd = format!("diff {from} {to} -s");
+//     let opts = str_to_args(&cmd).into_iter().peekable();
+//     let params = diffutilslib::params::parse_params(opts).unwrap();
+//
+//     // TODO need function because main cannot be called.
+//     group.bench_function(format!("diff files changed, lines: {num_lines}"), |b| {
+//         b.iter(|| diffutilslib::<diff>::cmp(&params).unwrap())
+//     });
+//
+//     group.finish();
+// }
+
+fn cmp_parse_only(cmd: &str) -> String {
+    let args = str_to_args(cmd).into_iter().peekable();
+    let _params = match diffutilslib::cmp::parse_params(args) {
+        Ok(params) => params,
+        Err(e) => {
+            return e.to_string();
+        }
+    };
+    return "ok".to_string();
+}
+
+fn diff_parse_only(cmd: &str) -> String {
+    let args = str_to_args(cmd).into_iter().peekable();
+    let _params = match diffutilslib::params::parse_params(args) {
+        Ok(params) => params,
+        Err(e) => {
+            return e.to_string();
+        }
+    };
+    return "ok".to_string();
+}
+
+fn str_to_args(opt: &str) -> Vec<OsString> {
+    let s: Vec<OsString> = opt
+        .split(" ")
+        .into_iter()
+        .map(|s| OsString::from(s))
+        .collect();
+
+    s
+}
+
+/// Generates two test files for comparison.
+///
+/// Each line consists of 10 words with 5 letters, giving a line length of 60 bytes.
+/// If num_differences is set, '*' will be inserted between the first two words of a line,
+/// evenly spaced in the file. 1 will add the change in the last line, so the comparison takes longest.
+fn generate_test_files(
+    lines: usize,
+    num_differences: usize,
+    dir: &Path,
+) -> std::io::Result<(String, String)> {
+    let f1 = format!("{FROM_FILE}_{lines}.txt");
+    let f2 = format!("{TO_FILE}_{lines}.txt");
+    let from_path = dir.join(f1);
+    let to_path = dir.join(f2);
+
+    generate_file_fast(&from_path, &to_path, lines, num_differences)?;
+
+    Ok((
+        from_path.to_string_lossy().to_string(),
+        to_path.to_string_lossy().to_string(),
+    ))
+}
+
+// Largely Gemini AI Generated
+fn generate_file_fast(
+    from_name: &Path,
+    to_name: &Path,
+    line_count: usize,
+    num_differences: usize,
+) -> std::io::Result<()> {
+    let file_from = File::create(from_name)?;
+    let file_to = File::create(to_name)?;
+    let change = if num_differences == 0 {
+        0
+    } else {
+        line_count / num_differences
+    };
+    // Use a larger 128KB buffer for massive files
+    let mut writer_from = BufWriter::with_capacity(128 * 1024, file_from);
+    let mut writer_to = BufWriter::with_capacity(128 * 1024, file_to);
+    let mut rng = rand::rng();
+
+    // Each line: (5 chars * 10 words) + 9 spaces + 1 newline = 60 bytes
+    let mut line_buffer = [b' '; 60];
+    line_buffer[59] = b'\n'; // Set the newline once at the end
+
+    for i in (0..line_count).rev() {
+        // Fill only the letter positions, skipping spaces and the newline
+        for word_idx in 0..10 {
+            let start = word_idx * 6; // Each word + space block is 6 bytes
+            for i in 0..5 {
+                line_buffer[start + i] = rng.random_range(b'a'..b'z' + 1);
+            }
+        }
+
+        // Write the raw bytes directly to both files
+        writer_from.write_all(&line_buffer)?;
+        // make changes in the file
+        if num_differences == 0 {
+            writer_to.write_all(&line_buffer)?;
+        } else {
+            if i % change == 0 {
+                line_buffer[5] = b'*';
+            }
+            writer_to.write_all(&line_buffer)?;
+            line_buffer[5] = b' ';
+        }
+    }
+
+    writer_from.flush()?;
+    writer_to.flush()?;
+
+    Ok(())
+}
+
+#[allow(unused)]
+// fn bench_binary_execution(c: &mut BenchmarkGroup<'_, WallTime>) {
+fn bench_binary_execution_cmp(c: &mut Criterion) {
+    c.bench_function("GNU cmp", |b| {
+        b.iter(|| {
+            let _status = Command::new("cmp")
+                .arg("from_file_100000.txt")
+                .arg("to_file_100000.txt")
+                .arg("-s")
+                .status()
+                .expect("Failed to execute binary");
+
+            // assert!(status.success());
+        })
+    });
+
+    c.bench_function("cmp binary", |b| {
+        b.iter(|| {
+            let _status = Command::new("target/release/diffutils")
+                .arg("cmp")
+                .arg("from_file_100000.txt")
+                .arg("to_file_100000.txt")
+                .arg("-s")
+                // .arg("--lines")
+                // .arg(black_box("10000"))
+                .status()
+                .expect("Failed to execute binary");
+
+            // assert!(status.success());
+        })
+    });
+}