CentOS 5.x （Apache 2.2系）
Usage:
htpasswd [-cmdpsD] passwordfile username
htpasswd -b[cmdpsD] passwordfile username password
htpasswd -n[mdps] username
htpasswd -nb[mdps] username password
-c Create a new file.
-n Don't update file; display results on stdout.
-m Force MD5 encryption of the password.
-d Force CRYPT encryption of the password (default).
-p Do not encrypt the password (plaintext).
-s Force SHA encryption of the password.
-b Use the password from the command line rather than prompting for it.
-D Delete the specified user.
CentOS 7.x （Apache 2.4系）
Usage:
htpasswd [-cimBdpsDv] [-C cost] passwordfile username
htpasswd -b[cmBdpsDv] [-C cost] passwordfile username password
htpasswd -n[imBdps] [-C cost] username
htpasswd -nb[mBdps] [-C cost] username password
-c Create a new file.
-n Don't update file; display results on stdout.
-b Use the password from the command line rather than prompting for it.
-i Read password from stdin without verification (for script usage).
-m Force MD5 encryption of the password (default).
-B Force bcrypt encryption of the password (very secure).
-C Set the computing time used for the bcrypt algorithm
(higher is more secure but slower, default: 5, valid: 4 to 31).
-d Force CRYPT encryption of the password (8 chars max, insecure).
-s Force SHA encryption of the password (insecure).
-p Do not encrypt the password (plaintext, insecure).
-D Delete the specified user.
-v Verify password for the specified user.
とても勉強になりましたよ！！＜つづく＞