Do files have unique identifiers ?

ashleyxxx

I am curious if all files that have been created have a unique identifier such as movie files and image files and so on. And if so can it be done in php?

dagon

not sure what you are asking? file type?

ashleyxxx

dagon;10974030 wrote:
not sure what you are asking? file type?

No not file type. For example I have a movie file clip that is 3 min long and the total length of the movie is 30 min long. Is there some type of encryption inside the file that makes it unique to the other and can not be changed. Kind of like a MAC address.

big_nerd

ashleyxxx,

Every file format has different specifications.

Binary file formats such as movies, images, etc differ greatly. Some binary formats require an "end" record (for lack of better words) stating that it is the end of the file.

Some formats also carry records as to how long the movie is, its resolution/size, such as 320x240, etc.

Some movies can play just fine if they are clipped, as in, if that 3-minute movie is identical to the first 3 minutes of that 30 minute movie, and the file truncated (not using any movie editor, just snipped) it may look the same.

If you have questions regarding specific formats its best to search the file format specifications for it, that is generally geared towards developers wishing to support the file format.

That being said - every binary format is different, so there really is no one straight answer to the question, so it may be yes, but is most likely no.

The only parts of a file format that can not be changed are that specific identifiers are required, however their values can change, the fact that they are there can not, otherwise the format would not be valid and may be rendered unreadable.

I hope that helps...

ashleyxxx

big.nerd;10974054 wrote:
ashleyxxx,

Every file format has different specifications.

Binary file formats such as movies, images, etc differ greatly. Some binary formats require an "end" record (for lack of better words) stating that it is the end of the file.

Some formats also carry records as to how long the movie is, its resolution/size, such as 320x240, etc.

Some movies can play just fine if they are clipped, as in, if that 3-minute movie is identical to the first 3 minutes of that 30 minute movie, and the file truncated (not using any movie editor, just snipped) it may look the same.

If you have questions regarding specific formats its best to search the file format specifications for it, that is generally geared towards developers wishing to support the file format.

That being said - every binary format is different, so there really is no one straight answer to the question, so it may be yes, but is most likely no.

The only parts of a file format that can not be changed are that specific identifiers are required, however their values can change, the fact that they are there can not, otherwise the format would not be valid and may be rendered unreadable.

I hope that helps...

Yes it does greatly. I believe my answer is no. My other question is it possible to open up the file properties and view it in php?

bradgrafelman

ashleyxxx wrote:
My other question is it possible to open up the file properties and view it in php?

For simplicity's sake, I'll just say "no" because what you are referring to sounds like a GUI provided by Windows.

However, can you get that same information? Most likely, yes. For example, what are some common data you mind find on that GUI screen? Filesize? Use [man]filesize/man. Accessed time? Use [man]fileatime/man.

ashleyxxx

bradgrafelman;10974064 wrote:
For simplicity's sake, I'll just say "no" because what you are referring to sounds like a GUI provided by Windows.

However, can you get that same information? Most likely, yes. For example, what are some common data you mind find on that GUI screen? Filesize? Use [man]filesize/man. Accessed time? Use [man]fileatime/man.

I have one more question is it possible to access the meta data of a file through php?
Thank you guys for all your help

dagon

ashleyxxx;10974098 wrote:
I have one more question is it possible to access the meta data of a file through php?

yes, how depends on the particular file type

bradgrafelman

In other words, you have to tell us what kind of metadata you're talking about, since "metadata" means nothing other than "data about data" without some sort of context.