error while loading shared libraries: xxx.so.3: cannot open shared object file: No such file

问题：在终端运行 gnuplot时出现如下错误信息
- gnuplot: error while loading shared libraries: libgd.so.3: cannot open shared object file: No such file or directory
解决：在cat /etc/ld.so.conf文件中添加一行：
- /usr/local/lib
ref: https://blog.csdn.net/mahoon411/article/details/113576586?spm=1001.2101.3001.6661.1&utm_medium=distribute.pc_relevant_t0.none-task-blog-2%7Edefault%7ECTRLIST%7Edefault-1-113576586-blog-114613254.pc_relevant_aa&depth_1-utm_source=distribute.pc_relevant_t0.none-task-blog-2%7Edefault%7ECTRLIST%7Edefault-1-113576586-blog-114613254.pc_relevant_aa&utm_relevant_index=1