Ohlone College Web Team Blog

To make file readable by others (i.e., the “world”), set the directory containing the files to:

• drwxr-xr-x
  or
  755

and set the files in the directory to:

• -rwxr--r--
  or
  644

Explanation of file permissions

There are 3 classes of permissions:

1. User (sometimes referred to as “owner”)
2. Group
3. Others (sometimes referred to as “all” or “world”)

A common notation for permissions is a series of 10 characters, such as:

• drwxr-xr-x
• -rw-r--r--
• -rw-rw-rw-

The first character represents the file type:

• - regular file
• d directory

The remaining 9 characters represent 3 permissions for each of the 3 classes:

• r read on
• w write on
• x execute on
• - off

Directories must have execute permissions, such as:

• drwx------
• drwxr-xr-x (most common)
• drwxrwxr-x
• drwxrwxrwx

Executable program files, such as CGI scripts, must have execute permissions, such as:

• -rwxr-xr-x

Regular files must have read and/or write permissions, such as:

• -rw-r--r-- (most common)
• -rw-rw-rw-

Read, write, and execute permissions may also be represented in octal notation:

• 4 read on
• 2 write on
• 1 execute on
• - off

The octal values are added to result in desired read-write-execute permissions:

• 4 + 2 + 1 = 7 for read-write-execute permissions rwx
• 4 + 2 = 6 for read-write permissions rw-
• 4 + 1 = 5 for read-execute permissions r-x
• 4 = 4 for read permissions r--

Examples of common octal notations are:

• 755 is same as drwxr-xr-x
• 644 is same as -rw-r--r--

See File System Permissions in Wikipedia for more information.