In Unix like operating systems, what are the default read, write and execute permission values for owner, group and others on a newly created regular file, before applying any user specific umask?

Introduction / Context:
File permissions are central to security and access control in Unix like operating systems. When a regular file is created, the system assigns default permission bits, which may then be modified by the user or filtered by the umask. This question focuses on the conventional default permissions represented in numeric form for owner, group and others.

Given Data / Assumptions:

• We are dealing with a regular file, not a directory.
• The permissions are expressed as three digits owner group others.
• Each digit sums read as 4, write as 2 and execute as 1.
• We ignore the effect of user specific umask for this conceptual question.

Concept / Approach:
For regular files, it is common for systems to start with read and write permission for the owner and read only permission for group and others. This pattern corresponds to rw r r in symbolic form, which translates to 6 4 4 in numeric form, because 6 equals 4 plus 2 for read and write, while 4 represents read only. These defaults balance usability for the owner with some access for others, and can later be restricted by umask settings.

Step-by-Step Solution:
Step 1: Recall that numeric permission codes use 4 for read, 2 for write and 1 for execute. Step 2: Determine the typical default for the owner of a file, which is read and write, giving 4 plus 2 equals 6. Step 3: Determine the typical default for group and others, which is read only, giving 4. Step 4: Combine these into the triple 6 4 4, representing owner group others. Step 5: Select the option that explicitly matches 6 4 4 for owner, group and others and describes the associated read and write rights.

Verification / Alternative check:
If you create a file on many Unix like systems and then examine its permissions with the ls command before changing umask, you will often see something equivalent to rw r r for a simple text file. Documentation for default file creation modes in the kernel also supports this pattern, subject to reduction by umask. This observation backs up the choice of 6 4 4 as the default numeric representation.

Why Other Options Are Wrong:
Option B, 6 4 2, would give write only for others, which is unusual and potentially unsafe. Option C, 6 4 6, grants write permission to others as well, which is also not the standard safe default for newly created files. Option D, 6 6 6, would allow read and write for everyone, which is clearly too permissive in most environments and does not match typical default file creation rules.

Common Pitfalls:
One pitfall is confusing default file permissions with default directory permissions; directories often need execute permission to allow entering the directory. Another mistake is mixing in the effect of the user specific umask in conceptual questions, even though the question explicitly focuses on the underlying default before mask application. Always separate the base mode from the umask when reasoning about this topic.

Final Answer:
The default permission values are 6 4 4 for owner, group and others, meaning read and write for the owner and read only for group and others.