Endianess of machine

[fsanchez]

How can i find out if machine is big/little endian with C... i know big/little endian but dont know how to write program for it. I dont want code but just point me in right direction.

felipe

[Elysia]

Since endianess works on a byte-level, that means anything larger than one byte will be affected.
So create an integer of >= 2 bytes, fill it with a known value, then check its bytes one by one. Depending on the endianess, they will be appear in different order.

[nonoob]

By "checking its bytes" as Elysia suggested, it should be accessed one byte at a time after casting an integer to a byte array and looking at those elements. Or using a union to access the data type as integer or bytes.

[new_ink2001]

We would 'and' the variable against a known value (something with the high or low bits set e.g. 0x000F) and evaluate the result.

[fsanchez]

Since endianess works on a byte-level, that means anything larger than one byte will be affected.
So create an integer of >= 2 bytes, fill it with a known value, then check its bytes one by one. Depending on the endianess, they will be appear in different order.

If I have like int n=100... then what function is there in the C lib to check its byte one by one.

[dwks]

As nonoob explained you can check the bytes of an integer by casting it to a char*.

    short data = 0x1020;
    char *p = (char *)&data;

Now p[0] will be the first byte in the representation of data, and p[1] will be the second. If p[0] is 0x20 the machine is little endian, for example.

[fsanchez]

As nonoob explained you can check the bytes of an integer by casting it to a char*.

    short data = 0x1020;
    char *p = (char *)&data;

Now p[0] will be the first byte in the representation of data, and p[1] will be the second. If p[0] is 0x20 the machine is little endian, for example.

If n is short integer and n=42 then in binary it look like 0000000000101010 as short 2 bytes long on my machine... so in big endian first byte is 00000000 (0) and in litlle endian it is 00101010 (42) correcto?

[itCbitC]

If n is short integer and n=42 then in binary it look like 0000000000101010 as short 2 bytes long on my machine... so in big endian first byte is 00000000 (0) and in litlle endian it is 00101010 (42) correcto?

Yep!

[fsanchez]

gracias a todos and specially to dwks.

[Epy]

Sorry, just read the part about not wanting any code.