This module provides and interface to user and group information on Posix systems. In addition, it allows for changing user and group ids. When changing user and group settings for the calling process, bear in mind that:

• Changing user and groups of the calling process requires permission.
• The functions setgroups() and initgroups() are not part of the POSIX standard and therefore the derived predicates may not be present.

See also

- Please check the documentation of your OS for details on the semantics of this predicates.

 getuid(-UID) is det

UID is the real user ID of the calling process.

 getgid(-GID) is det

GID is the real group ID of the calling process.

 geteuid(-UID) is det

UID is the effective user ID of the calling process.

 getegid(-GID) is det

GID is the effective group ID of the calling process.

 getgroups(-GroupsIDs:list(integer)) is det

GroupsIDs is the set of supplementary group IDs of the calling process. Note that these are numeric identifiers. Use group_info/2 to obtain details on the returned group identifiers.

 user_info(+User, -UserData) is det

UserData represent the passwd information for User. User is either a numeric UID or a user name. The predicate user_data/3 can be used to extract information from UserData.

 user_data(?Field, ?UserData, ?Value)

Value is the value for Field in UserData. Defined fields are:

name

Name of the user

password

Password hash of the user (or x if this is not accessible)

uid

Numeric user id of the user

gid

Numeric primary group id of the user

comment

The gecos field

home

Home directory of the user

shell

Default (login) shell of the user.

 group_info(+Group, -GroupData) is det

GroupData represent the group information for Group. Group is either a numeric GID or a group name. The predicate group_data/3 can be used to extract information from GroupData.

 group_data(?Field, ?GroupData, ?Value)

Value is the value for Field GroupData. Defined fields are:

name

Name of the user

password

Password hash of the user (or x if this is not accessible)

gid

Numeric group id of the group

members

List of user-names that are member of this group.

 setuid(+UID)

Set the user id of the calling process.

 seteuid(+UID)

Set the effective user id of the calling process.

 setgid(+GID)

Set the group id of the calling process.

 setegid(+GID)

Set the effective group id of the calling process.

 initgroups(+User, +Group) is det

Initialise the group access list of the calling process to the registered groups for User and the group Group. This predicate is only available if the underlying OS provides it.

 setgroups(+Groups:list(integer)) is det

Set the group access list of the caling process to the indicated groups. This predicate is only available if the underlying OS provides it.

 set_user_and_group(+User) is det

 set_user_and_group(+User, +Group) is det

Set the UID and GID to the User. User is either a UID or a user name. If Group is not specified, the primary group of User is used. If initgroups/2 is available, the resulting group access list of the calling process consists of the registered groups for User and the specified Group.

Re-exported predicates

The following predicates are exported from this file while their implementation is defined in imported modules or non-module files loaded by this module.

 set_user_and_group(+User) is det

 set_user_and_group(+User, +Group) is det

Set the UID and GID to the User. User is either a UID or a user name. If Group is not specified, the primary group of User is used. If initgroups/2 is available, the resulting group access list of the calling process consists of the registered groups for User and the specified Group.