tokio-pager: An asynchronous, Tokio-friendly pager

Unfortunately, Rust's pager crate does not play nicely with Tokio. It leaves threads open after the Tokio runtime exits, resulting in a nasty I/O error after a CLI program using both pager and a Tokio runtime exits. This may be due to the fact that the pager crate actually runs the pager in the parent process, meaning that the Tokio runtime, in the child process, exits before the pager, leaving dangling file descriptors and the aforementioned I/O error from Tokio.

Enter tokio-pager. This crate exports a Pager struct that allows the use of a pager subprocess in a way that plays nicely with Tokio.

Pager pipes its output to program specified in the $PAGERenvironment variable, except under two conditions:

1. If the value of $PAGER is cat, /usr/bin/cat, or anything that ends in /cat (/bin/cat, etc.), then the output is not paged at all (cat is not launched).
2. If stdout is not a TTY, such as when output is being redirected to a file, the output is not paged.

Pager respects the value of the $LESS environment variable (with some caveats—see PagerEnv::pager_env() for details).

Pager support

Right now, tokio-pager only works with less, but support for other pagers is planned in the future.