フォルダー構造

$ tree -L 2
.
├── Cargo.lock
├── Cargo.toml
├── src
│   └── main.rs
└── target
    └── debug

Cargo.toml

[package]
name = "sqlite3_update"
version = "0.1.0"
edition = "2018"

[dependencies]
rusqlite = "*"
chrono = "0.4"

src/main.rs

// --------------------------------------------------------------------
/*
	sqlite3_update/src/main.rs

					Jul/23/2020
*/
// --------------------------------------------------------------------
use std::env;
use rusqlite::{params, Connection, Result};
use chrono::{Local, Date};

// --------------------------------------------------------------------
fn main() -> Result<()> {
	eprintln! ("*** start ***");

	let args: Vec<_> = env::args().collect();
	let file_sqlite3 = &args[1];
	let key_in = &args[2];
	let population_in = &args[3];

	eprintln!("{}",file_sqlite3);
	eprintln!("{}",key_in);
	eprintln!("{}",population_in);

	let date_mod: Date<Local> = Local::today();
	println!("{}", date_mod);

	let conn = Connection::open(file_sqlite3).unwrap();

	let sql_str = "update cities set population = ".to_owned()
		+ population_in + &", date_mod = '".to_owned()
		+ &date_mod.to_string()
		+ &"' where id = '".to_owned() + key_in + "'";

	eprintln!("{}",sql_str);

	conn.execute(&sql_str,params![],)?;

	eprintln! ("*** end ***");

	Ok(())
}

// --------------------------------------------------------------------

実行

$ cargo run /var/tmp/sqlite3/cities.db t0713 3512600
    Finished dev [unoptimized + debuginfo] target(s) in 1.24s
     Running `target/debug/sqlite3_update /var/tmp/sqlite3/cities.db t0713 3512600`
*** start ***
/var/tmp/sqlite3/cities.db
t0713
3512600
2020-07-23+09:00
update cities set population = 3512600, date_mod = '2020-07-23+09:00' where id = 't0713'
*** end ***