I'm trying to write some scripts for doing some simple housekeeping tasks in mercurial and one of the things I frequently need to do is check if the working set is "empty" (depending on context, that could mean untracked files or modified tracked files).
The hg status command exits with exit status 0 unless there was an internal error, in which case it exits with exit status 255.
If a few of my scripts, I'm doing something silly like capturing the output of the hg status command and checking whether it's empty or not.
In other cases I'm checking the exit status of hg id -i | grep -qvF + to check whether there are dirty tracked files.
Both of these seem a little brittle. Are there dedicated subcommands for "querying" the repository to see if there are "untracked files" or "dirty tracked files" or "removed files" or various other interesting things in the working set?
hg status is the command to check for modifications of the working directory with respect to the checked-out revision - thus you are doing the right thing.
You can get away with exclusively using hg status. Using the --mard (or --modified --added --removed --deleted) flags will yield empty if the tracked files didn't change. And using -u or --unknown will show files which are neither ignored nor tracked - and empty output should always indicate no changes to tracked files nor any non-ignored files (but there might be new files which match one of the ignore patterns).
The output format of these commands (at least in the English original, thus LC_ALL=C hg status) is treated by mercurial as API, thus you should be able to rely on it.
Depending on your actual use-case you might want to look at the mercurial command server - but for a script which runs occasionally it might be quite over the top.