I believe that the exact procedure below worked for me two weeks ago, but now it doesn't. I start with an RSA private key rsa.pem and generate my own self-signed certificate:openssl req -new -x509 -key rsa.pem -out rsa.certhen I try to create a p12 file:openssl pkcs12 -export -out rsa.p12 -inkey rsa.pem-in rsa.cerbut I only get the following message:Usage: pkcs12 [options]where options are-export       output PKCS12 file-chain        add certificate chain-inkey file   private key if not infile-certfile f   add all certs in f-CApath arg   - PEM format directory of CA's-CAfile arg   - PEM format file of CA's-name name  use name as friendly name-caname nm  use nm as CA friendly name (can be used more than once).-in  infile   input filename-out outfile  output filename-noout        don't output anything, just verify.-nomacver     don't verify MAC.-nocerts      don't output certificates.-clcerts      only output client certificates.-cacerts      only output CA certificates.-nokeys       don't output private keys.-info         give info about PKCS#12 structure.-des          encrypt private keys with DES-des3         encrypt private keys with triple DES (default)-seed         encrypt private keys with seed-aes128, -aes192, -aes256              encrypt PEM output with cbc aes-camellia128, -camellia192, -camellia256              encrypt PEM output with cbc camellia-nodes        don't encrypt private keys-noiter       don't use encryption iteration-nomaciter    don't use MAC iteration-maciter      use MAC iteration-nomac        don't generate MAC-twopass      separate MAC, encryption passwords-descert      encrypt PKCS#12 certificates with triple DES (default RC2-40)-certpbe alg  specify certificate PBE algorithm (default RC2-40)-keypbe alg   specify private key PBE algorithm (default 3DES)-macalg alg   digest algorithm used in MAC (default SHA1)-keyex        set MS key exchange type-keysig       set MS key signature type-password p   set import/export password source-passin p     input file pass phrase source-passout p    output file pass phrase source-engine e     use engine e, possibly a hardware device.-rand file:file:...              load the file (or the files in the directory) into              the random number generator-CSP name     Microsoft CSP name-LMK          Add local machine keyset attribute to private keyI'm just following previous posts:https://stackoverflow.com/questions/38841563/create-rsacryptoserviceprovider-object-using-rsa-private-key-file-in-c-sharphttps://stackoverflow.com/questions/10994116/openssl-convert-pem-containing-only-rsa-private-key-to-pkcs12
How to produce p12 file with RSA private key and self-signed certificate
encryption;openssl;ssl
Turns out to be a character encoding issue with the dashes, which is confused from copy & pasting. I just re-typed the command and it worked.