Compile, connect -- notes-2

1 Linux The dynamic shared libraries on the operating system are roughly divided into three categories 

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1、 Operating system level shared library and basic system tool library 
 For example libc.so, libz.so, libpthread.so wait , These system libraries will be placed in /lib and /usr/lib Below directory , If it is 64 Bit operating system , There will be /lib64 and /usr /lib64 Catalog . If the operating system has a graphical interface , Then there will be /usr/X11R6/lib Catalog , If it is 64 Bit operating system , also /usr/X11R6 /lib64 Catalog . There may also be other specific Linux System library directory of version .
 The completeness and correct version of these system library files , Ensured Linux The above programs can run normally .
2、 Application level system shared libraries 
 The operating system does not come with , But libraries that may be shared by many applications , Usually placed in /usr/local/lib and /usr/local/lib64 Under these two directories . Many programs you compile and install by yourself will automatically put /usr/local/lib Join in gcc Of -L Parameters , And when running, it automatically arrives /usr/local /lib Now go to find the shared library .
 The above two types of dynamic shared libraries , The application will automatically find them , It doesn't need your extra settings and worries . Why is that ？ Because these directories are added to the search path of dynamic link program by default .Linux The search path of the system shared library is defined in /etc/ld.so