Bash environment variable to include path of c libraries

Question

I built a C library (compiled from source) below my home folder and now I have to build a new package that depends on that library. When running the configure script I get the error
configure: error: The required <package> library was not found.

Is there an environment variable I can edit to make my script search the library's path?

I already tried LD_LIBRARY_PATH

Answer 1

• Many libraries use pkg-config, so tell it where to find your locally installed .pc files:

  export PKG_CONFIG_PATH="$LOCAL/lib/pkgconfig:$LOCAL/share/pkgconfig"
  

  (The system-wide directories will be included automatically.)

  Sometimes a library-specific command is used instead of the generic pkg-config; for example, krb5-config. In this case, point to your bin directory:

  export PATH="$LOCAL/bin:$PATH"
  

• If pkg-config is not used, you will have to manually point the compiler and linker to the right place.

  export CFLAGS="-I$LOCAL/include"     # for the C compiler
  export CXXFLAGS="-I$LOCAL/include"   # for the C++ compiler
  export LDFLAGS="-L$LOCAL/lib"        # for the linker
  

• ./configure --help will usually list a series of --with-feature=... options, which allow specifying locations of each library separately.

  Often, ./configure --help will also list environment variables for each library (such as CURL_CFLAGS and CURL_LIBS); look for "C compiler flags" or "linker flags" in the help text.

  If you often need more than one custom library, this will quickly become inconvenient; you should instead specify pkg-config path and cflags for all libraries at once.

• You may also need to point the loader to your library location while compiling. For Linux, it would be:

  export LD_LIBRARY_PATH="$LOCAL/lib"
  

  This shouldn't be necessary when running compiled programs; the linker will have added the correct paths to the compiled binary itself (look for "Library rpath" in readelf -d yourprogram if you want to check).

  For Mac OS X, setting DYLD_LIBRARY_PATH should have a similar effect; otool can be used for inspecting applications.

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In all examples above, $LOCAL will be the prefix you used when installing libraries; for example, if you did ./configure --prefix ~/usr, then use ~/usr here.

Answer 2

If you haven't installed the library, you'll need to pass its include path to your configure script, similar to what is described in this question.

LD_LIBRARY_PATH would be used after you get it compiled, so you can find the library at runtime.