thread 'main' panicked at 'Please supply a filename in the first argument.

[wardhills]

Nice project. Thank you.

When the project is run I get the following:

$ cargo run
    Finished dev [unoptimized + debuginfo] target(s) in 0.01s
     Running `target/debug/keepitsimple`
thread 'main' panicked at 'Please supply a filename in the first argument.', src/main.rs:20:38
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

I am new to Rust. Is there some argument I am missing?

If the RUST_BACKTRACE=1 is set it returns:

$ RUST_BACKTRACE=1 cargo run
Finished dev [unoptimized + debuginfo] target(s) in 0.01s
Running target/debug/keepitsimple
thread 'main' panicked at 'Please supply a filename in the first argument.', src/main.rs:20:38
stack backtrace:
0: rust_begin_unwind
at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/std/src/panicking.rs:517:5
1: core::panicking::panic_fmt
at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/core/src/panicking.rs:100:14
2: core::panicking::panic_display
at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/core/src/panicking.rs:64:5
3: core::option::expect_failed
at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/core/src/option.rs:1638:5
4: core::option::Option::expect
at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/core/src/option.rs:709:21
5: keepitsimple::main
at ./src/main.rs:20:26
6: core::ops::function::FnOnce::call_once
at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/core/src/ops/function.rs:227:5
note: Some details are omitted, run with RUST_BACKTRACE=full for a verbose backtrace.

Thanks for any help.