Convert from .cer to .pem

openssl x509 -inform der -in myCert.cer -out certificate.pem

openssl pkcs7 -in myCert.cer -print_certs -out certificate.pem
unable to load PKCS7 object
1234345:error:09FFF06C:PEM routines:CRYPTO_internal:no start 
line:/System/Volumes/Data/SWE/macOS/BuildRoots/b8ff8433dc/Library/Caches/com.apple.xbs/Sources/libressl/libressl- 75/libressl-2.8/crypto/pem/pem_lib.c:684:Expecting: PKCS7

Related

• openssl pkcs12

See also

• openssl [ rand | s_client | passwd | openssl req | openssl rsa | openssl genrsa | openssl x509 | openssl ca | openssl verify | openssl ec | openssl dgst | openssl pkcs12 | openssl asn1parse | openssl help | .cer to .pem, openssl version