How to check Linux version with Autoconf?

Question

My program requires at least Linux 2.6.26 (I use timerfd and some other Linux-specific features).

I have an general idea how to write this macro but I don't have enough knowledge about writing test macros for Autoconf. Algorithm:

1. Run "uname --release" and store output
2. Parse output and subtract Linux version number (MAJOR.MINOR.MICRO)
3. Compare version

I don't know how to run command, store output and parse it.

Maybe such macro already exists and it's available (I haven't found any)?

Answer 1

I think you'd be better off detecting the specific functions you need using AC_CHECK_FUNC, rather than a specific kernel version. This will also prevent breakage if you find yourself cross-compiling at some point in the future

Answer 2

There is a macro for steps 2 (parse) and 3 (compare) version, ax_compare_version. For example:

linux_version=$(uname --release)
AX_COMPARE_VERSION($linux_version, [eq3], [2.6.26],
    [AC_MSG_NOTICE([Ok])],
    [AC_MSG_ERROR([Bad Linux version])])

Here I used eq3 so that if $linux_version contained additional strings, such as -amd64, the comparison still succeeds. There is a plethora of comparison operators available.