The chmod command uses a permission string as its argument to define access rights for a file. One common format is a three-digit number, where each digit represents the permission level for a different category of users:
Owner (the file creator)
Group (a group of users you define)
World (all other users on the file system)
Each digit is calculated based on the permissions granted to that category:
Read = 4
Write = 2
Execute = 1
By adding these values together, you create combinations of permissions.
0 = no permissions whatsoever; this person cannot read, write, or execute the file
1 = execute only
2 = write only
3 = write and execute (1+2)
4 = read only
5 = read and execute (4+1)
6 = read and write (4+2)
7 = read and write and execute (4+2+1)
Permissions are given using these digits in a sequence of three: one for owner, one for group, one for world.
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Viper FTP User Guide
