FairCom ISAM for C

File Permissions

When FairCom DB creates a file, the User ID of the creating user is assigned to the file as the file’s owner. The owner’s default group is also assigned to the file unless the creating function specifies one of the owner’s other Group ID’s.

Further, the user may specify a permission mask that determines the kind of access that users may acquire on subsequent opens. The mask is comprised of three components: owner permissions, group permissions and world permissions. With this structure, you are able to allow different users different levels of access to the file.

When the owner of a file opens that file, that user is given owner’s permissions. Typically this level allows the user the most flexibility in managing the file. If a user who is not an owner of the file opens that file, FairCom DB looks at the groups the user belongs to. If that user is a member of the group assigned to the file then the user is granted group permissions. Finally, a user not falling into these categories is granted world permissions. Generally, permissions become more restrictive as you go from owner to world.

For example, an owner of a file may be able to read, write, and update records, and delete the file if necessary. Another user who is a member of the group for that file could have permission to read, write, and update records, but not to delete the file. Finally, a user who is not an owner, and not a member of the file’s group, may have permission only to read the file.

Permission Mask

When the file is created you will provide a permission mask for that file. The permission mask is formed by OR-ing the appropriate permission constants (found in ctport.h) from the following list:

Permission Constant	Description
OPF_READ	owner read permission
OPF_WRITE	owner write/update permission
OPF_DEF	owner file definition permission
OPF_DELETE	owner file deletion permission
OPF_ALL	owner granted all permissions
OPF_NOPASS	owner grants read only without password
GPF_NONE	group access denied
GPF_READ	group read permission
GPF_WRITE	group write/update permission
GPF_DEF	group file definition permission
GPF_DELETE	group file deletion permission
GPF_NOPASS	group read only access without password
WPF_NONE	world access denied
WPF_READ	world read permission
WPF_WRITE	world write/update permission
WPF_DEF	world file definition permission
WPF_DELETE	world file deletion permission
WPF_NOPASS	world read only access without password

• “READ” permission grants access to data, but no ability to change the data.
• “WRITE” permission grants update abilities.
• “DEF” permission allows the user to change or set file definition characteristics such as alternative collating sequences and record schemas.
• “DELETE” permission grants the ability to delete the entire file.

For example, to grant the owner all permissions, to grant group members read and update permissions, and to permit no access outside of the group, the permission mask should be defined as:

(OPF_ALL | GPF_READ | GPF_WRITE | WPF_NONE)

If no permission mask is assigned to the file, owner, group and world are granted all permissions. Permission masks, file ownership and group assignment may also be changed by using the Security() function, or by the system administrator.