Thread: C interface libpq.so.2 problem

Hi ,

as a new user I have followed the Momjian libpq sample program format

#include "libpq-fe.h"

and cc -I/usr/local/pgsql/include -o myapp myapp.c
-L/usr/local/pgsql/lib -lpq

my application compiles but on execution gives

libpq.so.2: cannot open shared object file

Similar problems have been listed before but none of the suggestions fixed
my problem.
Does anyone recognise this problem?

Thanks

David McLennan



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<tt>dsmclennan@spipowernet.com.au schrieb:</tt><blockquote type="CITE"><tt>Hi ,</tt><p><tt>as a new user I have
followedthe Momjian libpq sample program format</tt><p><tt>#include "libpq-fe.h"</tt><p><tt>and cc
-I/usr/local/pgsql/include-o myapp myapp.c</tt><br /><tt>-L/usr/local/pgsql/lib -lpq</tt><p><tt>my application compiles
buton execution gives</tt><p><tt>libpq.so.2: cannot open shared object file</tt><br /> </blockquote><tt>This looks like
aninstallation problem! Your program is ok, but</tt><br /><tt>when it tries to load the libpq.so it fails. The idea of
theshared</tt><br /><tt>objects (that is what .so means; like the DLL in wind*ws) is to</tt><br /><tt>have a library in
aspecific version and use an _unspecific_ name</tt><br /><tt>for it.</tt><p><tt>So the library libpq.so is a symbolic
linkto libpq.so.<major> and</tt><br /><tt>this one could / should be a link to
libpq.so.<major>.<minor>where</tt><br /><tt><major> and <minor> refer to the concrete version
ofthe library.</tt><p><tt>It looks, like your lipq.so is a symbolic link to a nonexistent</tt><br /><tt>library
libpq.so.2(or that file may have unsufficient rights).</tt><br /><tt>Perhaps it's best you check your files; and make
shurethat you are</tt><br /><tt>looking at the right ones. The libraries are searched according to</tt><br /><tt>the
entriesin /etc/modules.conf (after changing this file a</tt><br /><tt>ldconfig is needed).</tt><p><tt>Newer Postgres
versions(or maybe all versions that you compile</tt><br /><tt>yourself) install their libraries under
/usr/local/pgsql/lib.</tt><br/><tt>Maybe you had older versions directly from your distribution</tt><br /><tt>in
/usr/libor /usr/i486-linux-libc5/lib or</tt><br /><tt>/usr/i486-linux-libc6/lib. In this case all depends on
the</tt><br/><tt>searchpath for the libraries.</tt><p><tt>You can use 'ldd yourprogram' to find out, which libraries
it</tt><br/><tt>depends on. If your program doesn't directly need the libpq.so</tt><br /><tt>you can check out all
librariesit uses for their dependencies.</tt><p><tt>Arrrgh, STOP! I just recognized, that some programs/libs
directly</tt><br/><tt>require the libpq.so.2 (not just the generic name libpq.so). If</tt><br /><tt>this is the case
withyour program, it seems that you just don't</tt><br /><tt>have any libpq.so on your system or forgot to write the
library-</tt><br/><tt>path into the above mentioned file /etc/modules.conf (on older</tt><br /><tt>systems there was a
/etc/conf.modules- so check this out).</tt><p><tt>Hope this helps</tt><p><tt>Andreas</tt>