113 lines
3.5 KiB
Rust
113 lines
3.5 KiB
Rust
use clap::{value_parser, Arg, ArgAction, ArgMatches, Command};
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use crate::Path;
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use std::fs;
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use std::io::{stdin, Read};
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use std::process;
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pub const PATH: Path = Path::Bin;
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pub fn cli() -> Command {
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Command::new("head")
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.version(env!("CARGO_PKG_VERSION"))
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.author("Nathan Fisher")
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.about("Display first lines of a file")
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.long_about(
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"Print the first 10 lines of each FILE to standard output.\n\
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With more than one FILE, precede each with a header giving the file name.\n\
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With no FILE, or when FILE is -, read standard input.\n\
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Mandatory arguments to long options are mandatory for short options too."
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)
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.args([
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Arg::new("FILES")
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.help("The input file to use")
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.num_args(1..),
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Arg::new("BYTES")
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.help("Count bytes instead of lines")
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.short('c')
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.long("bytes")
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.action(ArgAction::SetTrue),
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Arg::new("QUIET")
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.help("Disable printing a header. Overrides -c")
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.short('q')
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.long("quiet")
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.action(ArgAction::SetTrue),
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Arg::new("HEADER")
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.help("Each file is preceded by a header consisting of the string \"==> XXX <==\" where \"XXX\" is the name of the file.")
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.short('v')
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.long("verbose")
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.action(ArgAction::SetTrue),
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Arg::new("LINES")
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.help("Count n number of lines (or bytes if -c is specified).")
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.short('n')
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.long("lines")
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.default_value("10")
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.value_parser(value_parser!(usize))
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])
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}
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fn head(file: &str, count: usize, header: bool, bytes: bool) {
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let mut contents = String::new();
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if file == "-" {
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match stdin().read_to_string(&mut contents) {
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Ok(_) => true,
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Err(e) => {
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eprintln!("head: {}", e);
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process::exit(1);
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}
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};
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} else {
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let buf = fs::read_to_string(file);
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contents = match buf {
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Ok(c) => c,
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Err(e) => {
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eprintln!("head: {}", e);
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process::exit(1);
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}
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};
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}
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if header {
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println!("==> {} <==", file);
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}
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if bytes {
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for (index, char) in contents.chars().into_iter().enumerate() {
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if index < count {
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print!("{}", char);
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} else {
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println!();
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return;
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}
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}
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println!();
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} else {
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for (index, line) in contents.lines().into_iter().enumerate() {
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if index < count {
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println!("{}", line);
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} else {
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return;
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}
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}
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}
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}
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pub fn run(matches: &ArgMatches) {
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let files = match matches.get_many::<String>("FILES") {
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Some(c) => c.map(std::string::ToString::to_string).collect(),
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None => vec!["-".to_string()],
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};
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let header = !matches.get_flag("QUIET") && { files.len() > 1 || matches.get_flag("HEADER") };
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for (index, file) in files.into_iter().enumerate() {
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if index == 1 && header {
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println!();
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}
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head(
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&file,
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match matches.get_one("LINES") {
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Some(c) => *c,
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None => 10,
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},
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header,
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matches.get_flag("BYTES"),
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);
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}
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}
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