notmuch:tldr:5e6c1
The notmuch count command is used to count the number of matched email messages in the Notmuch database based on a given search criteria.
In this specific command, the --output=${select} option is used to specify the format of the output. The ${select} is a placeholder that is replaced with a specific value later in the command.
The ${search_term} is another placeholder that represents the search term or query that defines the criteria for selecting the email messages.
So, when you run this command in a terminal, it will count the number of email messages that match the provided search term, and the output will be formatted according to the value of ${select}. The values that can be used for ${select} are typically predefined formats such as tags, threads, paths, etc.