About
so means shared object file and are shared library in Linux
There format is the Executable and Linkable Format.
As Shared Library, so files are open file opened by a process.
The shared library extension is operating system dependent:
- .so for Linux, Solaris, or AIX,
- .sl for HP-UX.
Articles Related
Management
Search Path
When an executable is looking for a dynamic library (.so file), the linker searches in order:
- in the directories listed in the LD_LIBRARY_PATH environment variable
- in the directories listed in the executable's rpath. /usr/lib
- directories on the system search path. For instance:
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin
PATH
Dynamically linked libraries are typically placed in directories.
The usual directories include:
Path | Description |
---|---|
/lib | |
/usr/lib | Standard system libraries |
/gnu/lib | Gnu libraries |
/lib/security | PAM modules |
/usr/X11R6/lib or /usr/openwin/lib | X-windows |
/usr/local/lib | 3rd party libraries |
On GNU glibc-based systems, including all Linux systems, the list of directories automatically searched during program start-up is stored in the file /etc/ld.so.conf.
cat /etc/ld.so.conf
include ld.so.conf.d/*.conf
To control this process, you can use the LD_PATH environment variable (for instance: LD_LIBRARY_PATH for Linux/Solaris)
Content (Unpack)
readelf -a -W /path/To/SoFile
Version
Soname
In an ELF file:
- The version info in not explicitly stored . The full version is usually stored as a part of the library file name.
- The soname contains the name of the library which includes the major version. If there was an API change, the library creator is supposed to change the soname. Multiple libraries can then be on a single system.
Example: libtest.so
- libtest.so.1.0.1 - The library file itself, containing the full version
- libtest.so.1 - Symlink to libtest.so.1.0.1, having the same name as soname
- libtest.so - Symlink to libtest.so.1 used for linking.
To get the soname:
readelf -d /path/to/library.so | grep SONAME
File
The version is just to be found in the symbolic link.
libc below is the version 2.5
file /lib64/libc.so.6
/lib64/libc.so.6: symbolic link to `libc-2.5.so'
File Attribute (Symlink or file info)
File System - ( Symbolic | ln | Soft) link - File Alias - Symlink - Junction - Reparse Points
file libodbc.so
# if it's a symlink
libodbc.so: symbolic link to `libodbc.so.2.0.0'
# if it's file
libodbc.so: ELF 64-bit LSB shared object, AMD x86-64, version 1 (SYSV), not stripped
Load Test
dltest /path/to/driverFile.so
Dependency
- ldd (list dynamic dependencies) print shared library dependencies
ldd ../product/fmw/Oracle_BI1/bifoundation/odbc/lib/libodbc.so
ldd: warning: you do not have execution permission for `../product/fmw/Oracle_BI1/bifoundation/odbc/lib/libodbc.so'
linux-vdso.so.1 => (0x00007fff375c4000)
libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f7bc07ba000)
librt.so.1 => /lib64/librt.so.1 (0x00007f7bc05b0000)
libodbcinst.so => /u01/app/oracle/product/fmw/Oracle_BI1/bifoundation/odbc/lib/libodbcinst.so (0x00007f7bc03ca000)
libSEicu23.so => /u01/app/oracle/product/fmw/Oracle_BI1/bifoundation/odbc/lib/libSEicu23.so (0x00007f7bbf7b9000)
libdl.so.2 => /lib64/libdl.so.2 (0x00007f7bbf5b4000)
libstdc++.so.5 => /usr/lib64/libstdc++.so.5 (0x00007f7bbf2d9000)
libm.so.6 => /lib64/libm.so.6 (0x00007f7bbf056000)
libc.so.6 => /lib64/libc.so.6 (0x00007f7bbecfd000)
libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007f7bbeaef000)
/lib64/ld-linux-x86-64.so.2 (0x00000035bb600000)
List Shared Library used by processes
With the lsof
- one process
lsof -p $(pgrep nqsserver) | awk '{print $9}' | grep .so$
- all process from a root directory
lsof /path/to*
Find a shared library
sudo find / | grep whatever.so
- Example
sudo find / | grep libodbc.so
/tmp/infa_rpm/Domain/ce908432ad08b4beffd072ef5344365b/infa_rpm.tar/ODBC7.1/lib/libodbc.so
/tmp/unixODBC-2.3.6/DriverManager/.libs/libodbc.so.2.0.0
/tmp/unixODBC-2.3.6/DriverManager/.libs/libodbc.so.2
/tmp/unixODBC-2.3.6/DriverManager/.libs/libodbc.so
/usr/local/lib/libodbc.so.2.0.0
/usr/local/lib/libodbc.so.2
/usr/local/lib/libodbc.so
Creation
Example with Sqlite and an amalgam adapted from the Ref documentation
gcc \
-Wl,-soname,libsqlite3.so.0 \
-DDISABLE_DIRSYNC \
-DENABLE_COLUMN_METADATA \
-DENABLE_FTS3 \
-DENABLE_RTREE \
-DENABLE_JSON1 \
-DENABLE_UNLOCK_NOTIFY \
-DSECURE_DELETE \
-DTEMP_STORE=1 \
-DTHREADSAFE=1 \
-shared \
-o libsqlite3.so \
-fPIC \
sqlite3.c