Bash script to download the fmt library (C++)

download_fmt_library.sh

#!/bin/bash

# Copyright (c) 2020 Maurizio Tomasi
#
# This Bash script downloads the "fmt" C++ library and installs it in
# the current directory.

FMT_VERSION="7.1.2"

download_file() {
    filename="$1"
    dest="$2"

    if [ -z "$dest" ]; then
        dest=$filename
    fi

    destdir=$(dirname "$dest")
    if [ -n "$destdir" ]; then
        mkdir -p "$destdir"
    fi

    printf "Downloading file '%s' (version %s)\n" "$filename" "$FMT_VERSION"
    curl -s "https://raw.githubusercontent.com/fmtlib/fmt/${FMT_VERSION}/$filename" > "$dest"
}

echo "Going to download fmt library version ${FMT_VERSION} in current directory"
echo "Press ENTER to continue, or Ctrl+C to quit…"
read -s

for filename in fmt/core.h fmt/format.h fmt/format-inl.h; do
    download_file "include/$filename" "$filename"
done

download_file src/format.cc format.cc

cat > fmtlib.h <<EOF
#pragma once

#ifndef __has_include
    // No way to check if <format> exists, so play safe
    #include "fmt/format.h"
#else
    #if __has_include(<format>)
        // Hurrah, we're using a C++20 compiler!
        #include <format>
        namespace fmt = std::format;
    #else
        // No full C++20 support
        #include "fmt/format.h"
    #endif
#endif
EOF

cat <<EOF
The library has been downloaded. To use it, include in your C++ files the lines

    #include "fmtlib.h"

and be sure to add "format.cc" to your Makefile, e.g.:

    myprogram: myprogram.cc routines.cc format.cc
        c++ -o \$@ -g -Wall -std=c++11 \$^
EOF