macos - Why openssl is keg only?

Question

I see openssl is keg only. By default, the environment variables are not set. If I set them, will it cause any problems? When will it be safe to export those environment variables? Thanks.

$ brew info openssl
[email protected]: stable 1.1.1i (bottled) [keg-only]
Cryptography and SSL/TLS Toolkit
https://openssl.org/
/usr/local/Cellar/[email protected]/1.1.1i (8,067 files, 18.5MB)
  Poured from bottle on 2020-12-15 at 14:16:15
From: https://github.com/Homebrew/homebrew-core/blob/HEAD/Formula/[email protected]
License: OpenSSL
==> Caveats
A CA file has been bootstrapped using certificates from the system
keychain. To add additional certificates, place .pem files in
  /usr/local/etc/[email protected]/certs

and run
  /usr/local/opt/[email protected]/bin/c_rehash

[email protected] is keg-only, which means it was not symlinked into /usr/local,
because macOS provides LibreSSL.

If you need to have [email protected] first in your PATH run:
  echo 'export PATH="/usr/local/opt/[email protected]/bin:$PATH"' >> /Users/pengy/.bash_profile

For compilers to find [email protected] you may need to set:
  export LDFLAGS="-L/usr/local/opt/[email protected]/lib"
  export CPPFLAGS="-I/usr/local/opt/[email protected]/include"

For pkg-config to find [email protected] you may need to set:
  export PKG_CONFIG_PATH="/usr/local/opt/[email protected]/lib/pkgconfig"

==> Analytics
install: 865,212 (30 days), 2,335,532 (90 days), 7,780,134 (365 days)
install-on-request: 139,840 (30 days), 367,526 (90 days), 1,113,042 (365 days)
build-error: 0 (30 days)

Answer 1

等待大神答复