How to map chmod access permissions to an integer

Question

I came across a piece of code where chmod permissions are getting mapped to an integer.

33204 // -rw-rw-r--
36863 // -rwsrwsrwt
36855 // -rwsrwSrwt
36799 // -rwSrwsrwt
36351 // -rwsrwsrwx
36343 // -rwsrwSrwx

How are these permissions mapped to an integer number?

I am trying to find what permissions these numbers 33261, 41453 map to? I looked at various links, but I could find one that converts permissions into a number. Can someone help me with the conversion? Thanks in advance!

Answer 1

They only make "sense" in octal. Here's the first line using one of my programs to convert:

$ hex 33204
33204: 33204 0100664 0x81b4 text "\201\264" utf8 \350\206\264

The 0100664 means it's a regular file with read/write (user), read/write (group) and read-only (other). The chmod manual pages should mention this, but the first bit (the S_IFREG value) is not mentioned — even by POSIX — as often as the other flags. Here's an example from a header:

#define S_IFMT  00170000
#define S_IFSOCK 0140000
#define S_IFLNK  0120000
#define S_IFREG  0100000
#define S_IFBLK  0060000
#define S_IFDIR  0040000
#define S_IFCHR  0020000
#define S_IFIFO  0010000
#define S_ISUID  0004000
#define S_ISGID  0002000
#define S_ISVTX  0001000

Further reading:

• understanding and decoding the file mode value from stat function output