Implement nice (resolves #215)

Makefile

@@ -98,6 +98,7 @@ UNIX_PROGS := \
   kill \
   logname \
   mkfifo \
+  nice \
   nohup \
   timeout \
   tty \

src/nice/nice.rs

@@ -0,0 +1,115 @@
+#![crate_name = "nice"]
+
+/*
+ * This file is part of the uutils coreutils package.
+ *
+ * (c) Arcterus <arcterus@mail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+#![feature(macro_rules)]
+
+extern crate getopts;
+extern crate libc;
+
+use std::io::IoError;
+use std::os;
+use std::ptr;
+use libc::{c_char, c_int, execvp};
+
+const NAME: &'static str = "nice";
+const VERSION: &'static str = "1.0.0";
+
+// XXX: PRIO_PROCESS is 0 on at least FreeBSD and Linux.  Don't know about Mac OS X.
+const PRIO_PROCESS: c_int = 0;
+
+#[path = "../common/util.rs"]
+mod util;
+
+extern {
+    fn getpriority(which: c_int, who: c_int) -> c_int;
+    fn setpriority(which: c_int, who: c_int, prio: c_int) -> c_int;
+}
+
+pub fn uumain(args: Vec<String>) -> int {
+    let opts = [
+        getopts::optopt("n", "adjustment", "add N to the niceness (default is 10)", "N"),
+        getopts::optflag("h", "help", "display this help and exit"),
+        getopts::optflag("V", "version", "output version information and exit"),
+    ];
+
+    let matches = match getopts::getopts(args.tail(), &opts) {
+        Ok(m) => m,
+        Err(err) => {
+            show_error!("{}", err);
+            return 125;
+        }
+    };
+
+    if matches.opt_present("version") || matches.opt_present("help") {
+        println!("{} v{}", NAME, VERSION);
+        if matches.opt_present("help") {
+            let usage = getopts::usage("Run COMMAND with an adjusted niceness, \
+                                        which affects process scheduling.\n\
+                                        With no COMMAND, print the current \
+                                        niceness.  Niceness values range from \
+                                        at\nleast -20 (most favorable to the \
+                                        process) to 19 (least favorable to the\
+                                        \nprocess).", &opts);
+            println!("");
+            println!("Usage:");
+            println!("  {} [OPTIONS] [COMMAND [ARGS]]", NAME);
+            println!("");
+            print!("{}", usage);
+        }
+        0
+    } else {
+        let mut niceness = unsafe { getpriority(PRIO_PROCESS, 0) };
+        if os::errno() != 0 {
+            show_error!("{}", IoError::last_error());
+            return 125;
+        }
+
+        let adjustment = match matches.opt_str("adjustment") {
+            Some(nstr) => {
+                if matches.free.len() == 0 {
+                    show_error!("A command must be given with an adjustment.
+                                 Try \"{} --help\" for more information.", args[0]);
+                    return 125;
+                }
+                match from_str(nstr.as_slice()) {
+                    Some(num) => num,
+                    None => {
+                        show_error!("\"{}\" is not a valid number", nstr);
+                        return 125;
+                    }
+                }
+            },
+            None => {
+                if matches.free.len() == 0 {
+                    println!("{}", niceness);
+                    return 0;
+                }
+                10 as c_int
+            }
+        };
+
+        niceness += adjustment;
+        unsafe { setpriority(PRIO_PROCESS, 0, niceness); }
+        if os::errno() != 0 {
+            show_warning!("{}", IoError::last_error());
+        }
+
+        unsafe {
+            let executable = matches.free[0].to_c_str().into_inner();
+            let mut args: Vec<*const i8> = matches.free.iter().map(|x| x.to_c_str().into_inner()).collect();
+            args.push(ptr::null());
+            execvp(executable as *const c_char, args.as_ptr() as *mut *const c_char);
+        }
+
+        show_error!("{}", IoError::last_error());
+        if os::errno() as c_int == libc::ENOENT { 127 } else { 126 }
+    }
+}