First tool to master the use of is ldd

You use ldd to view the current library requirement list and where they are found it the current system.

[dev@squarepants stage]$ ldd tsmuxer
 linux-gate.so.1 => (0x00426000)
 libavfilter.so.6 => /home/dev/builds/tsmuxer/ort/stage/ffmpeg/lib/libavfilter.so.6 (0x00177000)
 libavformat.so.57 => /home/dev/builds/tsmuxer/ort/stage/ffmpeg/lib/libavformat.so.57 (0x0042b000)
 libavcodec.so.57 => /home/dev/builds/tsmuxer/ort/stage/ffmpeg/lib/libavcodec.so.57 (0xf61b0000)
 libswscale.so.4 => /home/dev/builds/tsmuxer/ort/stage/ffmpeg/lib/libswscale.so.4 (0x00b93000)
 libswresample.so.2 => /home/dev/builds/tsmuxer/ort/stage/ffmpeg/lib/libswresample.so.2 (0x00a29000)
 libavutil.so.55 => /home/dev/builds/tsmuxer/ort/stage/ffmpeg/lib/libavutil.so.55 (0x0034a000)
 libpthread.so.0 => /lib/libpthread.so.0 (0x00b39000)
 libudev.so.0 => /lib/libudev.so.0 (0x00866000)
 libdl.so.2 => /lib/libdl.so.2 (0x00b32000)
 librt.so.1 => /lib/librt.so.1 (0x00b56000)
 libX11.so.6 => /usr/lib/libX11.so.6 (0x00670000)
 libXv.so.1 => /usr/lib/libXv.so.1 (0x00967000)
 libXext.so.6 => /usr/lib/libXext.so.6 (0x003c0000)
 libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x00876000)
 libm.so.6 => /lib/libm.so.6 (0x003d2000)
 libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x00e55000)
 libc.so.6 => /lib/libc.so.6 (0x00c1e000)
 /lib/ld-linux.so.2 (0x00977000)
 libxcb.so.1 => /usr/lib/libxcb.so.1 (0x003fc000)
 libXau.so.6 => /usr/lib/libXau.so.6 (0x00427000)

It is also useful when libraries are missing, it will tell you which.

Let say after deployment on the customer system you have this error.

output:./tsmuxer: error while loading shared libraries: libavfilter.so.6: wrong ELF class: ELFCLASS64

Then use ldd to check what is going on

[root@localhost ~]# ldd tsmuxer
 linux-gate.so.1 => (0x002a7000)
 libavfilter.so.6 => not found
 libavformat.so.57 => not found
 libavcodec.so.57 => not found
 libswscale.so.4 => not found
 libswresample.so.2 => not found
 libavutil.so.55 => not found
 libpthread.so.0 => /root/./../lib/libpthread.so.0 (0x0024d000)
 libudev.so.0 => not found
 libdl.so.2 => /root/./../lib/libdl.so.2 (0x0085b000)
 librt.so.1 => /root/./../lib/librt.so.1 (0x00fef000)
 libX11.so.6 => /usr/lib/libX11.so.6 (0x00e39000)
 libXv.so.1 => /usr/lib/libXv.so.1 (0x00120000)
 libXext.so.6 => /usr/lib/libXext.so.6 (0x00125000)
 libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x00137000)
 libm.so.6 => /root/./../lib/libm.so.6 (0x009d3000)
 libgcc_s.so.1 => /root/./../lib/libgcc_s.so.1 (0x007ae000)
 libc.so.6 => /root/./../lib/libc.so.6 (0x002a8000)
 /lib/ld-linux.so.2 (0x00b89000)
 libxcb.so.1 => /usr/lib/libxcb.so.1 (0x00222000)
 libXau.so.6 => /usr/lib/libXau.so.6 (0x004e2000)

Fixing library issues with patchelf

patchelf --set-rpath '$ORIGIN/lib' <application-binary>

What patchref does is edit the path that tells where to look for the libraries. It edits the binary directly. So you do this once, then redistribute that binary and the lib folder.

In my case I excecuted

./patchelf --set-rpath '$ORIGIN/tsmuxer-lib' tsmuxer

The post Linux libraries 101 and distributing them with your app appeared first on Techy Things.

Zip code database in UK is not free. However some people put together some database in the public domain :

http://www.freepostcodes.org.uk
http://www.doogal.co.uk/UKPostcodes.php

Canada

not free

USA

free

The post Free UK, Canada, USA zip and postcodes databases appeared first on Techy Things.