Hard-coding paths in Linux

Coming from Windows background here.

Is it an acceptable practice for GUI Linux applications t开发者_如何学Goo store their data files (not user-specific) at hard-coded locations (e. g. /etc/myapp/stuff)? I couldn't find any syscalls that would return the preferred directory for app data. Is there a convention out there as to what goes where?

/opt/appname/stuff according to the Linux Filesystem Hierarchy Standard

Your distribution's packaging system likely provides ways to handle common installation paths. What distribution are you using?

Generally speaking, yes there is a convention. On most Linux systems, application configuration files are typically located at /etc/appname/. You'll want to consult the LSB (Linux Standard Base) and the Linux FHS (Filesystem Hierarchy Standard) for their respective recommendations.

Also, if you are targeting your application towards a specific Linux distro, then that distro vendor probably has their own specific recommendations as far as packaging and related-conventions are concerned. You'll want to look at your distro vendor's developer pages for more information.

Configuration files for processes with elevated privileges are generally stored in /etc. Data files for processes with elevated privileges (Web Server, Mail Server, Chat Server, etc.) are generally stored in /var. And that's where consistency ends. Some folks say you start with the location to store them (/etc|/var) then have an appname sub-folder for your app, then continue from there as necessary.

If you're not a system daemon with elevated privileges, your only consistent choice is a dot directory in the launching user's home directory. I think the Free Desktop Standards (XDG) specify ~/.config for per-user configuration, and ~/.cache for replaceable static and/or generated data you need to save.

Looking at my Home Directory, a few key dot directories I have are: ~/.cache ~/.config ~/.irssi ~/.maildir ~/.mozilla ~/.kde ~/.ssh ~/.vnc

[edit]
While not a syscall, the XDG specifications I reference are at http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html

There are certain conventions.

• System-wide, readable/editable (text-based) configuration files go in /etc/appname/.
• System-wide, per-machine binary data files that change (eg. binary databases) go in /var/*/appname/ - /var/cache/appname/, /var/spool/appname/ and /var/lib/appname/ are the most common.
• System-wide binary data files that could notionally be shared between machines (eg. things like graphics and sound files) go in /usr/share/appname/.

The full paths that Unix/Linux/GNU applications use to store config files and other data is usually set when an application is configured prior to compilation. These paths then get hard-coded into the compiled binary (you can see examples of this by running strings(1) over some existing executables).

That is, these types of paths are build-time configurable, not run-time configurable by default. Many apps will support command line options to specify where a configuration file is, and that configuration file will usually contain paths for other application resources. This allows an application to run with minimal configuration (built-in paths) but also allows a site to customise the paths completely.

Under Linux, only the basic services (opening a file, doing networking and interprocess communication etc) are provided as system calls. The rest is done using libraries.

If you are coding a GUI application, you should look into your toolkit's documentation to see if it provides a mechanism for managing defaults. Both KDE and Gnome have one for instance.