add -0, --unix-to-utc

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "utcnow"
-version = "1.0.0"
+version = "1.1.0"
 authors = ["Jonathan Strong <jonathan.strong@gmail.com>"]
 edition = "2018"
 

src/main.rs

@@ -1,7 +1,9 @@
 #![allow(unused)]
-
+use std::str::FromStr;
 use chrono::{DateTime, Utc, NaiveDateTime};
 
+const ONE_SECOND: u64 = 1_000_000_000_u64;
+
 fn nanos(utc: DateTime<Utc>) -> u64 {
     (utc.timestamp() as u64) * 1_000_000_000_u64 + (utc.timestamp_subsec_nanos() as u64)
 }
@@ -18,7 +20,11 @@ fn timespec_to_utc(sec: i64, nsec: i32) -> DateTime<Utc> {
 }
 
 fn timespec_to_nanos(sec: i64, nsec: i32) -> u64 {
-    (sec as u64) * 1_000_000_000_u64 + (nsec as u64)
+    (sec as u64) * ONE_SECOND + (nsec as u64)
+}
+
+fn nanos_to_timespec(nanos: u64) -> (i64, i32) {
+    ((nanos / ONE_SECOND) as i64, (nanos % ONE_SECOND) as i32)
 }
 
 fn main() {
@@ -47,6 +53,7 @@ fn main() {
             .long("seconds")
             .short("s")
             .requires("unix")
+            .conflicts_with_all(&["rfc2822", "timespec"])
             .required(false)
             .takes_value(false))
         .arg(clap::Arg::with_name("timespec")
@@ -55,26 +62,62 @@ fn main() {
             .short("t")
             .required(false)
             .takes_value(false))
+        .arg(clap::Arg::with_name("null")
+            .short("0")
+            .long("null")
+            .help("terminate displayed time with null character instead of newline")
+            .takes_value(false)
+            .required(false))
+        .arg(clap::Arg::with_name("unix-to-utc")
+            .long("unix-to-utc")
+            .help("convert integer unix timestamp (nanoseconds precision) to iso datetime")
+            .takes_value(true)
+            .required(false)
+            .conflicts_with_all(&["unix", "seconds"]))
         .get_matches();
 
-    let (sec, nsec) = get_time();
+    
+    let (sec, nsec): (i64, i32) =
+
+        if let Some(ts_str) = args.value_of("unix-to-utc") {                            // either parse --unix-to-utc input
+            match u64::from_str(ts_str) {
+                Ok(nanos) => nanos_to_timespec(nanos),
+
+                Err(e) => {
+                    eprintln!("failed to parse timestamp (expected integer): {}", e);
+                    std::process::exit(1);
+                }
+            }
+        } else {                                                                        // or else get current time
+            get_time()
+        };
+
 
-    if args.is_present("timespec") {
-        println!("{},{}", sec, nsec);
-    } else if args.is_present("unix") {
-        if args.is_present("seconds") {
-            println!("{}", sec);
-        } else {
-            println!("{}", timespec_to_nanos(sec, nsec));
+    let endline = if args.is_present("null") { "\u{0}" } else { "\n" };                 // pick endline - \n unless -0
+
+
+    if args.is_present("timespec") {                                                    // display timespec
+        print!("{},{}{}", sec, nsec, endline);
+
+
+    } else if args.is_present("unix") {                                                 // display unix
+
+        if args.is_present("seconds") {                                                 // unix seconds
+            print!("{}{}", sec, endline);
+
+        } else {                                                                        // unix nanos
+            print!("{}{}", timespec_to_nanos(sec, nsec), endline);
         }
-    } else if args.is_present("rfc2822") {
 
-        println!("{}", timespec_to_utc(sec, nsec).to_rfc2822());
 
-    } else {
+    } else if args.is_present("rfc2822") {                                              // display rfc2822
+        print!("{}{}", timespec_to_utc(sec, nsec).to_rfc2822(), endline);
+
+
+    } else {                                                                            // display rfc3339
         // Debug view is iso format / rfc3339 that we want
         // Display has spaces - no go
         // to_rfc3339 uses +00:00 instead of Z, which I don't like
-        println!("{:?}", timespec_to_utc(sec, nsec));
+        print!("{:?}{}", timespec_to_utc(sec, nsec), endline);
     }
 }