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I have written a program that performs health checks on servers. One of its functions is that it can check whether or not a symlink exists. I am currently in the process of writing unit tests (for use with Travis CI), and I'm wondering if there are any symlinks that I can depend on being there on any Linux system.

For example, I currently unit test with /bin/sh, which is usually a symlink to something like /bin/bash.

Does Linux have a set of symlinks that are there by default?

closed as too broad by mattdm, Anthon, cuonglm, slm Jul 17 '15 at 16:48

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    Why not just make a symlink as part of the setup for the unit test? /bin/sh does not have to be a symlink. – jordanm Jul 17 '15 at 14:50
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    Linux is a kernel. Nothing else. The operating systems using Linux as kernel differ a lot. – yeti Jul 17 '15 at 14:51
  • There are a number standard symlinks in /proc, but I don't think there is any "universal" symlink in a real filesystem. The various distributions are quite different from one another, even if you consider, say, only desktop-class systems. – lcd047 Jul 17 '15 at 14:57
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No, because there is no standard Linux distribution. Linux is just a kernel, and doesn't specify anything about user-space, including file layout. If you want to narrow this down to a subset of Linux distributions, you might be able to find something (with, as you note, /bin/sh as a good candidate)

However, the kernel itself does have some special fileystems, notably /proc and /sys, which are part of the kernel directly, and which contain symlinks. Therefore, for example:

$ file /proc/$$/exe
/proc/7622/exe: symbolic link to `/usr/bin/bash'

However, I'm not sure I'd rely on this for your tests, because a) proc might actually not be available within every testing system, and b) since it's not a real filesystem, it seems a little dodgy. Why not just create your own symlink as part of your test?

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