linuxidc@linuxidc:~/work/cpp$ ls
add.c add.h add.o a.out mian.c
linuxidc@linuxidc:~/work/cpp$ rm a.out
linuxidc@linuxidc:~/work/cpp$ ar -r libadd.a add.o
ar: creating libadd.a
linuxidc@linuxidc:~/work/cpp$ ls
add.c add.h add.o libadd.a mian.c
linuxidc@linuxidc:~/work/cpp$ g++ mian.c -llibadd -L./ -static -o main
/usr/bin/ld: cannot find -llibadd
collect2: error: ld returned 1 exit status
linuxidc@linuxidc:~/work/cpp$ g++ mian.c -libadd -L./ -static -o main
/usr/bin/ld: cannot find -libadd
collect2: error: ld returned 1 exit status
linuxidc@linuxidc:~/work/cpp$ pwd
/home/linuxidc/work/cpp
linuxidc@linuxidc:~/work/cpp$ g++ mian.c -libadd -L/home/linuxidc/work/cpp -static -o main
/usr/bin/ld: cannot find -libadd
collect2: error: ld returned 1 exit status
linuxidc@linuxidc:~/work/cpp$ g++ mian.c -ladd -L/home/linuxidc/work/cpp -static -o main
linuxidc@linuxidc:~/work/cpp$ ls
add.c add.h add.o libadd.a main mian.c
linuxidc@linuxidc:~/work/cpp$ ./main
1+2=3
其他地方也要用的话
linuxidc@linuxidc:~/work$ ls
add.h cpp mian.c
linuxidc@linuxidc:~/work$ g++ mian.c -ladd -L./cpp -static -o main
linuxidc@linuxidc:~/work$ ls
add.h cpp main mian.c
linuxidc@linuxidc:~/work$ ./main
1+2=3
2 动态函数库的建立与使用
1.首先创建libmyadd.so，即利用add.c这个函数生成动态库
g++ -share -fPIC -o libmyadd.so add.c
-share指为共享的，-fPIC表示position independent code位置无关，这是动态库特性
2.指定动态库生成可执行文件，-L.表示当前文件夹，-lmyadd表示去找libmyadd.so这个动态库文件。
g++ main.c -L. -lmyadd
3.直接使用会抱错，找不到动态库，要指定动态库的路径
./a.out会报错
LD_LIBRARY_PATH=. ./a.out指定当前库的路径后在运行就可以了
4.如果要一直用，可以将.so文件的目录添加到/etc/ld.so.conf里面，然后再执行ldconfig就行了，具体如下面：
linuxidc@linuxidc:~/work/cpp$ ls
add.c add.h add.o main.c
linuxidc@linuxidc:~/work/cpp$ g++ -share -fPIC -o libmyadd.so add.c
g++: error: unrecognized command line option ‘-share’
linuxidc@linuxidc:~/work/cpp$ g++ -shared -fPIC -o libmyadd.so add.c
linuxidc@linuxidc:~/work/cpp$ ls
add.c add.h add.o libmyadd.so main.c
linuxidc@linuxidc:~/work/cpp$ g++ main.c -L. -lmyadd
linuxidc@linuxidc:~/work/cpp$ ls
add.c add.h add.o a.out libmyadd.so main.c
linuxidc@linuxidc:~/work/cpp$ ./a.out
./a.out: error while loading shared libraries: libmyadd.so: cannot open shared object file: No such file or directory
linuxidc@linuxidc:~/work/cpp$ LD_LIBRARY_PATH=. ./a.out
1+2=3
如果要永久使用的话该怎么办呢？
linuxidc@linuxidc:~/work/cpp$ ls
add.c add.h add.o a.out libmyadd.so main.c
linuxidc@linuxidc:~/work/cpp$ ./a.out 这里直接用会报错
./a.out: error while loading shared libraries: libmyadd.so: cannot open shared object file: No such file or directory
linuxidc@linuxidc:~/work/cpp$ vi /etc/ld.so.conf 在这个文件里面添加.so所在的目录就行了
linuxidc@linuxidc:~/work/cpp$ pwd
/home/linuxidc/work/cpp
linuxidc@linuxidc:~/work/cpp$ vi /etc/ld.so.conf
linuxidc@linuxidc:~/work/cpp$ sudo ldconfig
linuxidc@linuxidc:~/work/cpp$ ./a.out
1+2=3
例如，我的添加后的ld.so.conf文件就是这个样子：
include /etc/ld.so.conf.d/*.conf
/home/linuxidc/work/cpp
Linux公社的RSS地址：https://www.linuxidc.com/rssFeed.aspx