openssl x509 查看证书有效期

openssl x509 -in mosquitto-client.crt  -dates -noout 

notBefore=Jul 16 01:46:39 2021 GMT
notAfter=Oct 14 01:46:39 2021 GMT

openssl x509 -in mosquitto-client.crt  -enddate -noout

notAfter=Oct 14 01:46:39 2021 GMT

openssl x509 -in mosquitto-client.crt  -startdate -noout

notBefore=Jul 16 01:46:39 2021 GMT

openssl x509 -in mosquitto-client.crt  -dates

notBefore=Jul 16 01:46:39 2021 GMT
notAfter=Oct 14 01:46:39 2021 GMT
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
查看openssl x509帮助信息

openssl x509 -help

查看所有的证书信息

openssl x509 -in mosquitto-client.crt  -text

Certificate:

Data:
    Version: 3 (0x2)
    Serial Number: 0 (0x0)
    Signature Algorithm: sha256WithRSAEncryption
    Issuer: C = GB, ST = United Kingdom, L = Derby, O = Mosquitto, OU = CA, CN = mosquitto.org, emailAddress = roger@atchoo.org
    Validity
        Not Before: Jul 16 01:46:39 2021 GMT
        Not After : Oct 14 01:46:39 2021 GMT
    Subject: C = CN, ST = GD, L = GZ, O = GV, OU = RD, CN = const.net.cn, emailAddress = admin@const.net.cn
    Subject Public Key Info:

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