Final answer:
Unix access permissions are indicated by a 10-character string showing file type and read, write, execute permissions for owner, group, and others, providing file security in Unix.
Step-by-step explanation:
The layout of a Unix access permission string consists of 10 characters representing different permissions. The first character indicates the type of file, such as '-' for a regular file or 'd' for a directory.
The next nine characters are grouped into three sets of three characters each, indicating permissions for the owner, group, and others, respectively. Each set consists of 'r' for read, 'w' for write, and 'x' for execute permissions. If a character is replaced by a '-', it indicates the corresponding permission is not granted.
For example, the permission string -rw-r--r-- signifies that the file owner can read and write the file, members of the group can only read it, and others can also only read it. Permissions are essential for file security and system administration in Unix.