Trying to install rtl-sdr (through git clone git://git.osmocom.org/rtl-sdr.git) thanks to the instructions here but can't go further than make in the first sequence of instructions:
cd rtl-sdr/
mkdir build
cd build
cmake ../
make
At my first try I got the following error:
/rtl-sdr/src/librtlsdr.c:30:10: fatal error: libusb.h: No such file or directory
After locating this file:
/usr/include$ sudo locate libusb.h
/usr/include/libusb-1.0/libusb.h
I tried to replace the original #include <libusb.h> with #include <libusb-1.0/libusb.h> (as suggested here and here), which led to a different failure:
/rtl-sdr/build$ make
[ 6%] Built target convenience_static
Scanning dependencies of target rtlsdr
[ 9%] Building C object src/CMakeFiles/rtlsdr.dir/librtlsdr.c.o
[ 12%] Linking C shared library librtlsdr.so
[ 28%] Built target rtlsdr
[ 31%] Linking C executable rtl_test
librtlsdr.so.0.6git: undefined reference to `libusb_open'
librtlsdr.so.0.6git: undefined reference to `libusb_release_interface'
librtlsdr.so.0.6git: undefined reference to `libusb_close'
librtlsdr.so.0.6git: undefined reference to `libusb_get_string_descriptor_ascii'
librtlsdr.so.0.6git: undefined reference to `libusb_get_device_list'
librtlsdr.so.0.6git: undefined reference to `libusb_kernel_driver_active'
librtlsdr.so.0.6git: undefined reference to `libusb_alloc_transfer'
librtlsdr.so.0.6git: undefined reference to `libusb_bulk_transfer'
librtlsdr.so.0.6git: undefined reference to `libusb_reset_device'
librtlsdr.so.0.6git: undefined reference to `libusb_handle_events_timeout'
librtlsdr.so.0.6git: undefined reference to `libusb_get_device'
librtlsdr.so.0.6git: undefined reference to `libusb_exit'
librtlsdr.so.0.6git: undefined reference to `libusb_free_transfer'
librtlsdr.so.0.6git: undefined reference to `libusb_init'
librtlsdr.so.0.6git: undefined reference to `libusb_get_device_descriptor'
librtlsdr.so.0.6git: undefined reference to `libusb_free_device_list'
librtlsdr.so.0.6git: undefined reference to `libusb_claim_interface'
librtlsdr.so.0.6git: undefined reference to `libusb_control_transfer'
librtlsdr.so.0.6git: undefined reference to `libusb_submit_transfer'
librtlsdr.so.0.6git: undefined reference to `libusb_dev_mem_free'
librtlsdr.so.0.6git: undefined reference to `libusb_cancel_transfer'
collect2: error: ld returned 1 exit status
src/CMakeFiles/rtl_test.dir/build.make:96: recipe for target 'src/rtl_test' failed
make[2]: *** [src/rtl_test] Error 1
CMakeFiles/Makefile2:138: recipe for target 'src/CMakeFiles/rtl_test.dir/all' failed
make[1]: *** [src/CMakeFiles/rtl_test.dir/all] Error 2
Makefile:129: recipe for target 'all' failed
make: *** [all] Error 2
Note that this suggestion seems to be associated with a gcc compile option / link --cflags libusb-1.0 or -lusb-1.0 (cf. here and here) that I don't know where to find (since I'm using make, without being used to it).
I also tried to replace the original #include <libusb.h> with #include <usb.h> (as seen here) which led to:
/rtl-sdr/src/librtlsdr.c:97:2: error: unknown type name ‘libusb_context’
FYI libusb-1.0-0-dev and libusb-dev are already installed (as suggested here, I tried, eventhough I guess I already had it installed...):
/usr/include$ sudo apt install libusb-1.0-0-dev
libusb-1.0-0-dev is already the newest version (2:1.0.21-2).
~$ sudo apt install libusb-dev
libusb-dev is already the newest version (2:0.1.12-31).
And already installed rtl-sdr using apt:
sudo apt-get install rtl-sdr
rtl-sdr is already the newest version (0.5.3-13).
About my system: Linux version 5.4.0-58-generic gcc version 7.5.0 (Ubuntu 7.5.0-3ubuntu1~18.04). This install aims at being able to use a DVB-T dongle with GNU Radio, which requires this rtl-sdr install.
EDIT: after @Tsyvarev answer
pkg-config with sudo apt install pkg-configgit clone, new clean
git clone, new /build etc and then make, which worked !Removing the old repository clone & re-creating a clean /build was necessary, since trying to launch make in the old /build even after the install of pkg-config didn't work. Note that this implies that no change was needed on the #include <libusb.h> code line in src/librtlsdr.c.
As a side note, for those of you who end up here because they're trying to install the "RTL-SDR Source" block for GNU Radio, I suspect my problem was actually that I hadn't installed gr-osmosdr with sudo apt install gr-osmosdr after installing rtl-sdr with a simple sudo apt-get install rtl-sdr.
@Tsyvarev answer (see comment), which I put in the EDIT: at the end of my question. I re-post his solution here in order to close the question and mark it as solved.
pkg-config with sudo apt install pkg-configgit clone, new clean
git clone, new /build etc and then make, which worked !Removing the old repository clone & re-creating a clean /build was necessary, since trying to launch make in the old /build even after the install of pkg-config didn't work. Note that this implies that no change was needed on the #include <libusb.h> code line in src/librtlsdr.c.
As a side note, for those of you who end up here because they're trying to install the "RTL-SDR Source" block for GNU Radio, I suspect my problem was actually that I hadn't installed gr-osmosdr with sudo apt install gr-osmosdr after installing rtl-sdr with a simple sudo apt-get install rtl-sdr.