Adding a custom library to c programs

Question

I am using Ubuntu Linux I have made a custom static library Mylib.a, I can include it to only those c files which are in the same directory as the static library.

I want to make it a general library so that I can include the library file to any c file I want irrespective of its location

`gcc` will search in specific folders, see documentation for more details (you may start with `LIBRARY_PATH` environment variable and also compile with `-v` to see where it search). Alternatively you may give full path (anywhere it is) on `gcc` command line. — Adriano Repetti, Nov 24 '15 at 11:15
How do you include this library? You have to include the header and link the library. — terence hill, Nov 24 '15 at 11:33

score 4 · Answer 1 · edited May 23 '17 at 11:55

To use a static library you have to include the header in the .c files that use the library and then link the library. If the name of the library is libstatic.a then:

gcc -o yourprog yourprog.c -lstatic

If the library is not in the same directory use the -L option to specify the path:

gcc -o yourprog yourprog.c -L/path-to-lib -lstatic

(see also this post: How to link to a static library in C?)

score 3 · Accepted Answer · edited May 23 '17 at 10:29

3

You can copy that .a file (or better .so file) to a standard location such as /usr/lib.

If you compile from the command line, you also need to specify the library name (even if it's already in /usr/lib), the same way when you specify standard library like -lpthread.

You can also specify the library path and library name in makefile

edited May 23 '17 at 10:29

Community

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answered Nov 24 '15 at 11:18

artm

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I did copy it to /usr/lib but it still gives me compilation error – Ramesh Kamath Nov 24 '15 at 11:31
Is it link error or compilation error? Did you remember to copy the `.h` file to `/usr/include` as well? – artm Nov 24 '15 at 11:39
I did not copy the .h file – Ramesh Kamath Nov 24 '15 at 12:06
It works! I still have to mention the library name when I run the object file gcc -o ex ex.o -l_mylib Is there a way to add this library permanently to a MakeFile – Ramesh Kamath Nov 24 '15 at 19:40
Is there a way to create a custom lib that can be called without the -l ? (like -lpthread) – Nark Apr 05 '18 at 21:34

score 1 · Answer 3 · answered Nov 24 '15 at 11:12

As Adriano wrote, you can include a library even if it is not in the same directory as your c file. However, you have to specify where to look for for the libraries you use.

see here: https://gcc.gnu.org/onlinedocs/gcc/Directory-Options.html

Hope I helped,

Adding a custom library to c programs

3 Answers3