Although std::cout in C++ is powerful, it lacks the ease of use of format
string in Python. Fortunately, the 3rd party package fmt
provides a similar feature for C++.
Build fmt#
To use the fmt package, we need to build it:
git clone --depth 1 https://github.com/fmtlib/fmt.git
cd fmt
mkdir build && cd build
cmake -G "Unix Makefiles" -DCMAKE_INSTALL_PREFIX=~/tools/fmt -DCMAKE_BUILD_TYPE=Release ..
make -j 8
make install
This will build the static version of fmt and install it under
$HOME/tools/fmt.
To build a dynamic library, use the following cmake command instead:
cmake -G "Unix Makefiles" -DCMAKE_INSTALL_PREFIX=~/tools/fmt -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=TRUE ..
How to use#
Here is a short snippet to test it:
#include <iostream>
#include <vector>
#include <fmt/ranges.h>
#include <fmt/core.h>
using std::vector;
int main() {
vector<int> arr = {1, 2, 3};
fmt::print("arr is {}", arr);
fmt::print("The price of {} is {} Yuan/kg", "apple", 4.2);
return 0;
}
Use the following comamnd to build against the static version of fmt:
g++ -L$HOME/tools/fmt/lib64/ -I$HOME/tools/fmt/include/ test.cc -l:libfmt.a -o test_static
And the following command to build against the dynamic version of fmt:
g++ -L$HOME/tools/fmt/lib64/ -I$HOME/tools/fmt/include/ test.cc -lfmt -o test_shared
To run the dynamic executable, you need to set up the env variable
LD_LIBRARY_PATH properly:
LD_LIBRARY_PATH=$HOME/tools/fmt/lib64:$LD_LIBRARY_PATH ./test_shared
The size differs significantly between the static and dynamic executable files:
32K test_shared
220K test_static
References#
- Building fmt: https://fmt.dev/latest/usage.html#building
- Link library statically
- Use a cpp package: