partially functional printf

usr/src/mei/printf/Cargo.toml

@@ -10,3 +10,4 @@ path = "src/printf.rs"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+clap = { version = "4.4.8", features = ["derive"] }

usr/src/mei/printf/src/printf.rs

@@ -1,3 +1,92 @@
-fn main() {
-    println!("Hello, world!");
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License, Version 1.0 only
+ * (the "License").  You may not use this file except in compliance
+ * with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+
+/*
+ * Copyright 2023 Ren Kararou  All rights reserved.
+ * Use is subject to license terms.
+ */
+
+// man page is printf(1) [https://illumos.org/man/1/printf]
+// man page refs formats(7) [https://illumos.org/man/7/formats]
+//
+// returns 0 on success.  Any positive int return code is an error.
+// negative return codes are UB.
+//
+// must handle both escape sequences and format strings as defined primarily in formats(7) and
+// additionally in printf(1).  We will only be following the sections pertinent to /usr/bin/printf.
+
+use std::process::ExitCode;
+
+use clap::Parser;
+
+#[derive(Parser)]
+#[clap(disable_help_flag = true)]
+#[command(name = "printf")]
+struct Args {
+    format: Option<String>,
+    argument: Option<Vec<String>>,
+}
+
+#[inline]
+fn usage() {
+    eprintln!("usage: printf format [arguments ...]");
+}
+
+fn escape(escstr: String) -> String {
+    let escmap = vec![
+        ("\\\\", "\\"),
+        //("\\a", "\a"),
+        //("\\b", "\b"),
+        //("\\f", "\f"),
+        ("\\n", "\n"),
+        ("\\r", "\r"),
+        ("\\t", "\t"),
+        //("\\v", "\v"),
+    ];
+    let mut im = escstr;
+    for esc in escmap {
+        im = str::replace(im.as_str(), esc.0, esc.1);
+    }
+    // TODO: Handle octal esc
+
+    im.clone()
+}
+
+fn fmt(fmtstr: String) -> String {
+    fmtstr.clone()
+}
+
+fn main() -> ExitCode {
+    let args = Args::parse();
+
+    if args.format.clone().is_none() && args.argument.clone().is_none() {
+        usage();
+        return ExitCode::FAILURE;
+    }
+
+    if let Some(fmtstr) = args.format {
+        let fmtstr = escape(fmtstr.clone());
+        print!("{fmtstr}");
+    }
+
+    ExitCode::SUCCESS
 }