extern crate inotify;
extern crate getopts;
extern crate tail;
use std::path::Path;
use std::iter::Iterator;
use std::io::{Read, BufRead, Write, BufWriter};
use std::fs::File;
use std::collections::HashMap;
use inotify::{Inotify, WatchMask, EventMask};
use getopts::Options;
use tail::{StatefulFile, ModificationType, BackwardsReader};
#[allow(dead_code)]
static USAGE: &'static str = r#"Usage: tail [OPTION]... [FILE]...
Print the last 10 lines of each FILE to standard output.
With more than one FILE, precede each with a header giving the file name.
With no FILE, or when FILE is -, read standard input.
Mandatory arguments to long options are mandatory for short options too.
-c, --bytes=[+]NUM output the last NUM bytes; or use -c +NUM to
output starting with byte NUM of each file
-f, --follow output appended data as the file grows;
-F same as --follow=name --retry
-n, --lines=[+]NUM output the last NUM lines, instead of the last 10;
or use -n +NUM to output starting with line NUM
-q, --quiet never output headers giving file names
-v, --verbose always output headers giving file names
-h, --help display this help and exit
-V, --version output version information and exit
NUM may have a multiplier suffix:
b 512, kB 1000, K 1024, MB 1000*1000, M 1024*1024,
GB 1000*1000*1000, G 1024*1024*1024, and so on for T, P, E, Z, Y.
With --follow (-f), tail defaults to following the file descriptor, which
means that even if a tail'ed file is renamed, tail will continue to track
its end. This default behavior is not desirable when you really want to
track the actual name of the file, not the file descriptor (e.g., log
rotation). Use --follow=name in that case. That causes tail to track the
named file in a way that accommodates renaming, removal and creation.
"#;
fn print_usage() {
print!("{}", USAGE);
std::process::exit(0);
}
fn main() {
let args: Vec<String> = std::env::args().collect();
let mut opts = Options::new();
opts.optopt("c", "bytes", "output the last NUM bytes", "NUM");
opts.optflag("f", "follow", "output appended as the file grows");
opts.optflag("F", "", "same as follow with --retry");
opts.optopt("n", "lines", "output the last NUM lines, instead of the last 10", "NUM");
opts.optflag("h", "help", "print this help menu");
opts.optflag("V", "version", "version of program");
let matches = match opts.parse(&args[1..]) {
Ok(m) => m,
Err(f) => { panic!(f.to_string()) }
};
if matches.opt_present("h") {
print_usage();
}
if matches.opt_present("V") {
println!("tail version {}", env!("CARGO_PKG_VERSION"));
return;
}
if matches.free.is_empty() {
eprintln!("Error: Must have at least one file in arguments");
print_usage();
}
let follow_opt = matches.opt_present("f");
let num_of_lines = matches.opt_str("n").unwrap_or(String::from("10"));
let file_names: Vec<String> = matches.free;
let mut watcher = Inotify::init().expect("Inotify failed to initialize");
let mut files = HashMap::new();
for file_name in file_names {
let mut wd = watcher.add_watch(Path::new(&file_name), WatchMask::MODIFY)
.unwrap_or_else(|_| panic!("Failed to attach watcher to file: {}", &file_name));
let mut fd = File::open(&file_name)
.unwrap_or_else(|_| panic!("Failed to open file handle for: {}", &file_name));
let mut sf = StatefulFile::new(fd, file_name);
initial_print(&mut sf, &num_of_lines);
sf.update_cursor();
files.insert(wd, sf);
}
if follow_opt {
let mut buffer = [0u8; 4096];
loop {
let events = watcher.read_events_blocking(&mut buffer)
.expect("Failed to read inotify events");
for event in events {
if event.mask.contains(EventMask::MODIFY) {
let sf = files.get_mut(&event.wd).unwrap();
follow(sf);
}
}
}
}
}
fn follow(sf: &mut StatefulFile) {
match sf.modification_type() {
ModificationType::Added => {}
ModificationType::Removed => {
sf.reset_cursor();
}
ModificationType::NoChange => {}
}
sf.update_metadata();
sf.seek_to_cursor();
print_from_cursor(sf);
sf.update_cursor();
}
fn initial_print(sf: &mut StatefulFile, num_lines_str: &String) {
let mut writer = BufWriter::new(std::io::stdout());
if num_lines_str.starts_with("+") {
let line_iter = (&mut sf.fd).lines().map(|l| l.unwrap())
.skip(num_lines_str.chars().skip(1).collect::<String>().parse::<usize>()
.unwrap_or_else(|_| panic!("Incorrect number of lines given: {}", &num_lines_str)));
for line in line_iter {
writer.write(line.as_bytes()).unwrap();
writer.write(b"\n").unwrap();
}
writer.flush().unwrap();
return;
}
let num_lines = num_lines_str.parse::<usize>()
.unwrap_or_else(|_| panic!("Incorrect number of lines given: {}", &num_lines_str));
let mut reader = BackwardsReader::new(num_lines, &mut sf.fd);
reader.read_all(&mut writer);
writer.flush().unwrap();
}
fn print_from_cursor(sf: &mut StatefulFile) {
let mut writer = BufWriter::new(std::io::stdout());
for line in sf.fd.by_ref().lines().map(|l| l.unwrap()) {
writer.write(line.as_bytes()).unwrap();
writer.write(b"\n").unwrap();
}
writer.flush().unwrap();
}