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+# `ntfy-run`
+
+`ntfy-run` is a tool to run a command, capture its output, and send it to a
+`ntfy` server.
+
+It's designed to be similar to `cron`'s `MAILTO` feature, sending an email if
+the command running under `ntfy-run` generated any output, but this behaviour
+can be changed with flags.
+
+## Installation
+
+You can download a binary from GitHub releases or build it yourself:
+
+```bash
+git clone https://github.com/quantum5/ntfy-run.git
+cd ntfy-run
+cargo build --release
+sudo cp target/release/ntfy-run /usr/local/bin
+```
+
+## Usage
+
+All options can be specified on the command line, as both short and long
+options, but also as environment variables.
+
+### Basic Example
+
+Simple notification to an `ntfy.sh` URL:
+
+```bash
+NTFY_URL=https://ntfy.sh/hello ntfy-run echo 'Hello, world!'
+ntfy-run --ntfy-url https://ntfy.sh/hello echo 'Hello, world!'
+ntfy-run -n https://ntfy.sh/hello echo 'Hello, world!'
+```
+
+This will generate a notification with title `Success: echo 'Hello, world!'`
+and the following body:
+
+```
+exit status: 0
+==================== STDOUT ====================
+Hello, world!
+```
+
+For simplicity's sake, all subsequent commands will assume you have the
+environment variable `NTFY_URL=https://ntfy.sh/hello` set.
+
+### Authentication
+
+You can use the `-t` or `--token` flag (or the `NTFY_TOKEN` environment
+variable) to pass an access token to `ntfy`:
+
+```bash
+NTFY_TOKEN=tk_example ntfy-run echo 'Hello, world!'
+ntfy-run -t tk_example echo 'Hello, world!'
+```
+
+You can also use the `-u` or `--user` flag in combination with the `-p` or
+`--password` flag (or the `NTFY_USER` and `NTFY_PASSWORD` environment variables)
+to pass a user and password combination:
+
+```bash
+NTFY_USER=example NTFY_PASSWORD=hunter2 ntfy-run echo 'Hello, world!'
+ntfy-run -u example -p hunter2 echo 'Hello, world!'
+```
+
+### Filtering notifications
+
+By default, nothing is generated on successful executions that generate no
+output. For example, the following command generates no notification:
+
+```bash
+ntfy-run true
+```
+
+You can pass the `-N` or `--always-notify` flags, or `NTFY_ALWAYS_NOTIFY=true`
+environment variable to force a notification anyway:
+
+```bash
+ntfy-run -N true
+```
+
+You can also use the `-o` or `--only-failures` flags, or `NTFY_FAILURE_ONLY=true`
+environment variable to only notify on successful executions:
+
+```bash
+# No notification:
+ntfy-run -o echo 'Hello, world!'
+
+# Will generate a notifications:
+ntfy-run -o false
+ntfy-run -o sh -c 'echo "Hello, world!"; false'
+```
+
+### Message titles
+
+By default, the message title is `Success:` or `Failure:` followed by the
+command line. You can change the command line portion with the `-T` or `--title`
+flag, or the `NTFY_TITLE` environment variable:
+
+```bash
+# Title: Success: echo 'Hello, world!'
+ntfy-run echo 'Hello, world!'
+
+# Title: Success: my title
+ntfy-run -T 'my title' echo 'Hello, world!'
+```
+
+You can override the title on success or failure with the following flags:
+
+* `-s`, `--success-title` or `NTFY_SUCCESS_TITLE` environment variable; and
+* `-f`, `--failure-title` or `NTFY_FAILURE_TITLE` environment variable.
+
+```bash
+# Title: My action succeeded
+ntfy-run -s 'My action succeeded' echo 'Hello, world!'
+
+# Title: My action failed
+ntfy-run -f 'My action failed' false
+```
+
+### Message priorities and tags
+
+You can override the message priority on success or failure with the following
+flags:
+
+* `-S`, `--success-priority` or `NTFY_SUCCESS_PRIORITY` environment variable;
+  and
+* `-F`, `--failure-priority` or `NTFY_FAILURE_PRIORITY` environment variable.
+
+You can override the message tags on success or failure with the following
+flags:
+
+* `-a`, `--success-tags` or `NTFY_SUCCESS_TAGS` environment variable; and
+* `-A`, `--failure-tags` or `NTFY_FAILURE_TAGS` environment variable.
+
+```bash
+ntfy-run -S min -F max -a tada -A sob echo 'Hello, world!'
+ntfy-run -S min -F max -a tada -A sob false
+ntfy-run -S min -F max -a tada -A sob does-not-exist
+```
+
+Result:
+![example ntfy output for the above command](demo.png)
+
+### Email
+
+You can get `ntfy` to send an email alongside the notification by passing the
+`-e` or `--email` flag, or with the `NTFY_EMAIL` environment variable.
+
+### Icon
+
+You can get `ntfy` to display an icon by passing its URL as the `-i` or `--icon`
+flag, or with the `NTFY_ICON` environment variable.
+
+### `crontab`
+
+In `vixie-cron` and similar implementations, you can use `ntfy-run` as follows:
+
+```crontab
+NTFY_URL=https://ntfy.sh/hello
+NTFY_TOKEN=tk_example
+NTFY_ALWAYS_NOTIFY=true
+0 0 * * * ntfy-run backup-server
+```
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