If you open a *.gif file with notepad the file starts with GIF89
but for the *.jpeg files the first characters aren't something like GIF89
How can I detect that my file is *.jpeg with it's file first characters?
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On Linux, `libmagic1` may help. – mafso Jan 30 '15 at 19:11
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There is simple code snippet in C# that does exactly that, look at this [SO question](http://stackoverflow.com/questions/55869/determine-file-type-of-an-image). You can easily convert it to C or C++. – seva titov Jan 30 '15 at 19:14
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@S.T. was this question tagged "C#" originally maybe? It's not currently. – Drew Dormann Jan 30 '15 at 19:15
1 Answers
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According to The JPEG File Interchange Format:
- (After a 2 byte "SOI" marker...)
- the next 2 bytes will be
0xFFE0 - the next 2 bytes are unimportant for this detection
- the next 5 bytes will be
"JFIF"(including the null-terminator)
Drew Dormann
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what about .exe files? / can we detect that if a file is runable or not with it's contetn – user3105142 Feb 03 '15 at 21:11
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@user3105142 that's a new question. Feel free to ask it - you'll get a larger audience that way. – Drew Dormann Feb 03 '15 at 21:12
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:) I ask it in a new question [link](http://stackoverflow.com/questions/28308916/detect-the-file-format-with-its-content) – user3105142 Feb 03 '15 at 21:18