g++: error: pkg-config --cflags --libs opencv: No such file or directory

[DoSeek]

use bellow command build:
$ g++ -o encryption encryption.cpp 'pkg-config opencv --cflags --libs'
g++: error: pkg-config --cflags --libs opencv: No such file or directory

but change "apostrophe(')" in command as "back quote()", then build success, as: $ g++ -o encryption encryption.cpp pkg-config opencv --cflags --libs`