How can I view file header information?

Question

I looked at this question Mark PDF as Adobe PDF and one of the answers says:

In my document headers created with LibreOffice, the version 1.4 is having fewer header information.

What header information is this and how can I view it? For all type of files if possible.

Solution

you can use some command that read the hexadecimal of a file like hexdump and then read the header from the right panel example:

hexdump -C  Desktop/somefile | head

The output is:

00000000  ff d8 ff e0 00 10 4a 46  49 46 00 01 01 00 00 01  |......JFIF......|
00000010  00 01 00 00 ff fe 00 3b  43 52 45 41 54 4f 52 3a  |.......;CREATOR:|
00000020  20 67 64 2d 6a 70 65 67  20 76 31 2e 30 20 28 75  | gd-jpeg v1.0 (u|
00000030  73 69 6e 67 20 49 4a 47  20 4a 50 45 47 20 76 38  |sing IJG JPEG v8|
00000040  30 29 2c 20 71 75 61 6c  69 74 79 20 3d 20 39 30  |0), quality = 90|
00000050  0a ff db 00 43 00 03 02  02 03 02 02 03 03 03 03  |....C...........|
00000060  04 03 03 04 05 08 05 05  04 04 05 0a 07 07 06 08  |................|
00000070  0c 0a 0c 0c 0b 0a 0b 0b  0d 0e 12 10 0d 0e 11 0e  |................|
00000080  0b 0b 10 16 10 11 13 14  15 15 15 0c 0f 17 18 16  |................|
00000090  14 18 12 14 15 14 ff db  00 43 01 03 04 04 05 04  |.........C......|

as you see this show me that this file is a jpeg image.

Another option is xxd

xxd Desktop/somefile | head

gives same output of above.

Comments

[Parto]

Is this the same as mime type?

[Maythux]

@AvatarParto yes

[Parto]

But this seems to have more info than a mime type

[Maythux]

it looks like with more information please check this for more information freeformatter.com/mime-types-list.html

[Parto]

The mime type for a JPG is just 'image/jpeg'. The header file includes the creator and quality too. And I'm sure this info changes depending on the type of file.

[Maythux]

In the header all information about a file is found including the mime type, file size, and other metadata.. with more examples you may see the dates(creation/modification), and many other metadata. Those metadata are much useful in case of data recovery.. But in my answer i was just strict to reply your narrow needs. But in few words, header of a file will show you all available metadata

[Maythux]

@AvatarParto you are welcome Buddy. I'm glad to serve you