利用文件头标志判断文件类型

简介

我们都知道，文件的扩展名是用来识别文件类型的。通过给他指定扩展名，我们可以告诉自己，也告诉操作系统我们想用什么方式打开这个文件。比如我么会把.jpg的文件默认用图片显示软件打开，.zip 文件会默认用解压软件打开等等。

然而，扩展名完全是可以随便改改的。我们可以给文件设置一个任意的扩展名，当然也可以不设置扩展名。这样一来我们就不能了解到这个文件究竟是做什么的，究竟是个什么样的文件。我们或许也会疑惑，为什么一个软件，比如视频播放器，就能用正确的方式打开.mp4 .rmvb .wmv 等等的视频？

事实上，所有的文件都是以二进制的形式进行存储的，本质上没有差别。之所以使用的方法不同，只是因为我们理解他的方式不同。在每一个文件（包括图片，视频或其他的非ASCII文件）的开头（十六进制表示）实际上都有一片区域来显示这个文件的实际用法，这就是文件头标志。

Linux下我们可以用file命令直接查看文件的实际格式，但是他本质上也是利用文件头标志来进行文件类型判断的。下面就简要介绍下手动判断文件真实类型的方法。

表格

扩展名	文件头标识（HEX）	文件描述
123	00 00 1A 00 05 10 04	Lotus 1-2-3 spreadsheet (v9) file
3gg; 3gp; 3g2	00 00 00 nn 66 74 79 70 33 67 70	3rd Generation Partnership Project 3GPP (nn=0x14) and 3GPP2 (nn=0x20) multimedia files
7z	37 7A BC AF 27 1C	7-ZIP compressed file
aba	00 01 42 41	Palm Address Book Archive file
abi	41 4F 4C 49 4E 44 45 58	AOL address book index file
aby; idx	41 4F 4C 44 42	AOL database files: address book (ABY) and user configuration data (MAIN.IDX)
accdb	00 01 00 00 53 74 61 6E 64 61 72 64 20 41 43 45 20 44 42	Microsoft Access 2007 file
ACM	4D 5A	MS audio compression manager driver
ADF	44 4F 53	Amiga disk file
adx	03 00 00 00 41 50 50 52	Lotus Approach ADX file
AIFF	46 4F 52 4D 00	Audio Interchange File
ain	21 12	AIN Compressed Archive File
ami	5B 76 65 72 5D	Lotus Ami Pro
amr	23 21 41 4D 52	Adaptive Multi-Rate ACELP (Algebraic Code Excited Linear Prediction) Codec, commonly audio format with GSM cell phones
ANI	52 49 46 46
API	4D 5A 90 00 03 00 00 00	Acrobat plug-in
arc	1A 0x	LH archive file, old version(where x = 0x2, 0x3, 0x4, 0x8 or 0x9 for types 1-5, respectively)
arc	41 72 43 01	FreeArc compressed file
arj	60 EA	ARJ Compressed Archive
ARJ	60 EA 27
ART	4A 47 03 0E 00 00 00	AOL ART file
ART	4A 47 04 0E 00 00 00	AOL ART file
asf	30 26 B2 75 8E 66 CF 11	Windows Media
asf; wma; wmv	30 26 B2 75 8E 66 CF 11 A6 D9 00 AA 00 62 CE 6C	Microsoft Windows Media Audio/Video File(Advanced Streaming Format)
asx	3C	Advanced Stream redirector file
au	2E 73 6E 64	SoundMachine Audio File NeXT/Sun Microsystems μ-Law audio file
avi	41 56 49 20	Audio Video Interleave (AVI)
AX	4D 5A	Library cache file
AX	4D 5A 90 00 03 00 00 00	DirectShow filter
bag	41 4F 4C 20 46 65 65 64 62 61 67	AOL and AIM buddy list file
BAS	20 20 20
bin	42 4C 49 32 32 33 51	Thomson Speedtouch series WLAN router firmware
bmp	42 4D	Windows Bitmap
BMP	42 4D 3E
bz; bz2	42 5A 68	BZIP Archive
BZ2; TAR.BZ2; TBZ2; TB2	42 5A 68	bzip2 compressed archive
CAB	49 53 63
CAB; HDR	49 53 63 28	Install Shield v5.x or 6.x compressed file
CAB	4D 53 43 46	Microsoft CAB File Format
cat	30	Microsoft security catalog file
CBD	43 42 46 49 4C 45	WordPerfect dictionary file (unconfirmed)
CCD	5B 43 6C
cdr	CDR	Corel Draw
CDR	45 4C 49 54 45 20 43 6F 6D 6D 61 6E 64 65 72 20	Elite Plus Commander saved game file
CDR, DVF	4D 53 5F 56 4F 49 43 45	Sony Compressed Voice File
CHI; CHM	49 54 53 46	Microsoft Compiled HTML Help File
CHM	49 54 53
CLB	43 4D 58 31	Corel Binary metafile
CLB	43 4F 4D 2B	COM+ Catalog file
cnt	3A 42 61 73 65
COM, DLL, DRV, EXE, PIF, QTS, QTX, SYS	4D 5A	Windows/DOS executable file
COM	4D 5A EE
COM	E9 3B 03
CPE	46 41 58 43 4F 56 45 52 2D 56 45 52	Microsoft Fax Cover Sheet
CPL	4D 5A	Control panel application
CPT	43 50 54 37 46 49 4C 45	Corel Photopaint file
CPT	43 50 54 46 49 4C 45	Corel Photopaint file
CPX	5B 57 69
cru; crush	43 52 55 53 48	CRUSH Archive File
CRU	43 52 55 53 48 20 76	Crush compressed archive
CRW	49 49 1A 00 00 00 48 45 41 50 43 43 44 52 02 00	Canon digital camera RAW file
CTF	43 61 74 61 6C 6F 67 20 33 2E 30 30 00	WhereIsIt Catalog file
CUR	00 00 02 00 01 00 20 20	Windows cursor file
dat	03	MapInfo Native Data Format
dat	1A 52 54 53 20 43 4F 4D 50 52 45 53 53 45 44 20 49 4D 41 47 45 20 56 31 2E 30 1A	Runtime Software disk image
dat	41 56 47 36 5F 49 6E 74 65 67 72 69 74 79 5F 44 61 74 61 62 61 73 65	AVG6 Integrity database file
DAT	43 52 45 47	Windows 9x registry hive
DAT	43 6C 69 65 6E 74 20 55 72 6C 43 61 63 68 65 20 4D 4D 46 20 56 65 72 20	IE History DAT file
DAT	45 52 46 53 53 41 56 45 44 41 54 41 46 49 4C 45	Kroll EasyRecovery Saved Recovery State file
DAT	49 6E 6E 6F 20 53 65 74 75 70 20 55 6E 69 6E 73 74 61 6C 6C 20 4C 6F 67 20 28 62 29	Inno Setup Uninstall Log file
db	00 06 15 61 00 00 00 02 00 00 04 D2 00 00 10 00	Netscape Navigator (v4) database file
DB	44 42 46 48	Palm Zire photo database
db	08	dBASE IV or dBFast configuration file
db3	03	dBASE III file
db4	04	dBASE IV data file
dba	00 01 42 44	Palm DateBook Archive file
dbx	CF AD 12 FE
dbx	CF AD 12 FE C5 FD 74 6F	Outlook Express
dci	3C 21 64 6F 63 74 79 70	AOL HTML mail file
dcx	3A DE 68 B1	DCX Graphic File
DDB	00 01 00
dib	42 4D	device-independent bitmap image
DLL	4D 5A 90
DMP	4D 44 4D 50 93 A7	Windows minidump file
DMS	44 4D 53 21	Amiga DiskMasher compressed archive
doc	0D 44 4F 43	DeskMate Document file
doc	12 34 56 78 90 FF	MS Word 6.0
doc	31 BE 00 00 00 AB 00 00	MS Word for DOS 6.0
doc	7F FE 34 0A	MS Word
dot; ppt; xla; ppa; pps; pot; msi; sdw; db	D0 CF 11 E0	MS Office/OLE2
doc; dot; xls; xlt; xla; ppt; apr ;ppa; pps; pot; msi; sdw; db	D0 CF 11 E0 A1 B1 1A E1	MS Compound Document v1 or Lotus Approach APR file
DPL	4D 5A 50
DRV	4D 5A 16
drw	07	A common signature and file extension for many drawing programs.
drw	01 FF 02 04 03 02	Micrografx vector graphic file
ds4	4D 47 58 20 69 74 70 64	Micrografix Designer 4
DSN	4D 56	CD Stomper Pro label file
dsp	23 20 4D 69 63 72 6F 73 6F 66 74 20 44 65 76 6 56C 6F 70 65 72 20 53 74 75 64 69 6F	Microsoft Developer Studio project file
dss	02 64 73 73	Digital Speech Standard (Olympus, Grundig, & Phillips)
dtd	07 64 74 32 64 64 74 64	DesignTools 2D Design file
dtd	3C 21 45 4E 54 49 54 59	XML DTD
DVR	44 56 44	DVR-Studio stream file
dwg	41 43 31
Enn (where nn are numbers)	45 56 46	EnCase evidence file
ECO	2A 50 52
elf	7F 45 4C 46 01 01 01 00	ELF Executable
emf	01 00 00 00 58 00 00 00	Extended (Enhanced) Windows Metafile Format, printer spool file
eml	44 65 6C 69 76 65 72 79 2D 64 61 74 65 3A	Email
EML	46 72 6F 6D 20 20 20	A commmon file extension for e-mail files. Signatures shown here are for Netscape, Eudora, and a generic signature, respectively. EML is also used by Outlook Express and QuickMail.
EML	46 72 6F 6D 20 3F 3F 3F	A commmon file extension for e-mail files. Signatures shown here are for Netscape, Eudora, and a generic signature, respectively. EML is also used by Outlook Express and QuickMail.
EML	46 72 6F 6D 3A 20	A commmon file extension for e-mail files. Signatures shown here are for Netscape, Eudora, and a generic signature, respectively. EML is also used by Outlook Express and QuickMail.
EML	52 65 63
enc	00 5C 41 B1 FF	Mujahideen Secrets 2 encrypted file
enl	[32 byte offset] 40 40 40 20 00 00 40 40 40 40	EndNote Library File
eps	25 21 50 53	Adobe EPS File
eps	25 21 50 53 2D 41 64 6F 62 65	Postscript
eps	25 21 50 53 2D 41 64 6F 62 65 2D 33 2E 30 20 45 50 53 46 2D 33 20 30	Adobe encapsulated PostScript file (If this signature is not at the immediate beginning of the file, it will occur early in the file, commonly at byte offset 30)
EPS	C5 D0 D3
eth	1A 35 01 00	GN Nettest WinPharoah capture file
evt	30 00 00 00 4C 66 4C 65	Windows Event Viewer file
evt	03 00 00 00 C4 66 C4 56
EVTX	45 6C 66 46 69 6C 65 00	Windows Vista event log file
exe; dll; drv; vxd; sys; ocx; vbx	4D 5A	Win32 Executable
exe; dll; drv; vxd; sys; ocx; vbx	4D 5A	Win16 Executable
exe; com; 386; ax; acm; sys; dll; drv; flt; fon; ocx; scr; lrc; vxd; cpl; x32	4D 5A	Executable File
EXE, DLL, OCX, OLB, IMM, IME	4D 5A 90
fli	00 11 AF	FLIC Animation file
flt	00 01 01	OpenFlight 3D file
FLT	4D 5A 90 00 03 00 00 00	Audition graphic filter file (Adobe)
FLV	46 4C 56 01	Flash video file
fm	3C 4D 61 6B 65 72 46 69 6C 65 20	Adobe FrameMaker file
fm3	00 00 1A 00 07 80 01 00	Lotus 123 v3 FMT file
fmt	20 00 68 00 20 0	Lotus 123 v4 FMT file
FNT	43 48 41
FON	4D 5A	Font file
GBC	87 F5 3E
gid	3F 5F 03 00	Windows Help Index File
GID	4C 4E 02 00	Windows Help index file
GIF	47 49 46 38
gif	47 49 46 38 37 61	Graphics interchange format file (GIF 87A)
gif	47 49 46 38 39 61	Graphics interchange format file (GIF89A)
GTD	7B 50 72
GX2	47 58 32	Show Partner graphics file (not confirmed)
gz; tar; tgz	1F 8B	Gzip Archive File
gz; tgz	1F 8B 08	GZ Compressed File
hap	91 33 48 46	HAP Archive File
HDMP	4D 44 4D 50 93 A7	Windows heap dump file
hdr	23 3F 52 41 44 49 41 4E 43 45 0A	adiance High Dynamic Range image file
HLP	3F 5F 03
hlp	3F 5F 03 00	Windows Help file
HLP	4C 4E 02 00	Windows Help file
hlp	[7 byte offset] 00 00 FF FF FF FF	Windows Help file
hqx	28 54 68 69 73 20 66 69 6C 65	Macintosh BinHex 4 Compressed Archive
hqx	28 54 68 69 73 20 66 69 6C 65 20 6D 75 73 74 20 62 65 20 63 6F 6E 76 65 72 74 65 64 20 77 69 74 68 20 42 69 6E 48 65 78 20	Macintosh BinHex 4 Compressed Archive
HTM	3C 21 44
htm; html	3C 21 44 4F 43 54	HyperText Markup Language 3
htm; html	3C 48 54 4D 4C 3E	HyperText Markup Language 2
htm; html	3C 68 74 6D 6C 3E	HyperText Markup Language 1
html	68 74 6D 6C 3E	HTML
ico	00 00 01 00 00	Icon File
ico	00 00 01 00 01 00 20 20	Icon File
IFF	46 4F 52 4D
IFO	44 56 44	DVD info file
IME	4D 5A 90
img	00 01 00 08 00 01 00 01 01	Ventura Publisher/GEM VDI Image Format Bitmap file
IMG	00 FF FF
IMM	4D 5A 90
ind	41 4F 4C 49 44 58	AOL client preferences/settings file (MAIN.IND)
ISO	43 44 30 30 31	ISO-9660 CD Disc Image (This signature usually occurs at byte 8001, 8801, or 9001.)
ivr	2E 52 45 43	RealPlayer video file (V11 and later)
JAR	4A 41 52 43 53 00	JARCS compressed archive
jar	5F 27 A8 89	JAR Archive File
jpg; jpeg	FF D8 FF
jpg; jpe; jpeg	FF D8 FF E0 00	JPG Graphic File
jpg; jpe; jpeg	FF D8 FF FE 00	JPG Graphic File
KGB	4B 47 42 5F 61 72 63 68 20 2D	KGB archive
KOZ	49 44 33 03 00 00 00	Sprint Music Store audio file (for mobile devices)
LDB	42 49 4C
lha	2D 6C 68 35 2D	LHA Compressed
lha; lzh	[2 byte offset] 2D 6C 68	Compressed archive file
LHP	3F 5F 03
lhp	3F 5F 03 00	Windows Help File
lib	21 3C 61 72 63 68 3E 0A	Unix archiver (ar) files and Microsoft Program Library Common Object File Format (COFF)
LIB	2A 24 20
LIT	49 54 4F 4C 49 54 4C 53	Microsoft Reader eBook file
LNK	4C 00 00
lnk	4C 00 00 00	Windows Shortcut (Link File)
lnk	4C 00 00 00 01 14 02	Windows Link File
LNK	4C 00 00 00 01 14 02 00	Windows shortcut file
log	2A 2A 2A 20 20 49 6E 73 74 61 6C 6C 61 74 69 6F 6E 20 53 74 61 72 74 65 64 20	Symantec Wise Installer log file
lzh	lh	Lz compression file
lwp	57 6F 72 64 50 72 6F	Lotus WordPro v9
m3u	23 45 58
m4a	00 00 00 20 66 74 79 70 4D 34 41 20 00 00 00 00	Apple Lossless Audio Codec file
m4a; m4v	00 00 00 20 66 74 79 70 4D 34 41 20 00 00 00 00	QuickTime M4A/M4V file
manifest	3C 3F 78 6D 6C 20 76 65 72 73 69 6F 6E 3D	Windows Visual Stylesheet XML file
MAR	4D 41 52 31 00	Mozilla archive
MAR	4D 41 52 43	Microsoft/MSN MARC archive
MAR	4D 41 72 30 00	MAr compressed archive
max	D0 CF 11
mdb	00 01 00 00 53 74 61 6E 64 61 72 64 20 4A 65 74 20 44 42	Microsoft Access file
mdb; mda; mde; mdt	53 74 61 6E 64 61 72 64 20 4A	MS Access
MDF	00 FF FF
mdf	00 FF FF FF FF FF FF FF FF FF FF 00 00 02 00 01	Alcohol 120% CD image
mdf	01 0F 00 00	Microsoft SQL Server 2000 database
MDI	45 50	Microsoft Document Imaging file
MDS	4D 45 44
MID; MIDI	4D 54 68 64	Musical Instrument Digital Interface (MIDI) sound file
mkv	1A 45 DF A3 93 42 82 88 6D 61 74 72 6F 73 6B 61	Matroska stream file
MLS	4D 49 4C 45 53	Milestones v1.0 project management and scheduling software (Also see “MV2C” and “MV214” signatures)
MLS	4D 4C 53 57	Skype localization data file
MLS	4D 56 32 31 34	Milestones v2.1b project management and scheduling software (Also see “MILES” and “MV2C” signatures)
MLS	4D 56 32 43	Milestones v2.1a project management and scheduling software (Also see “MILES” and “MV214” signatures)
MMF	4D 4D 4D 44 00 00	Yamaha Corp. Synthetic music Mobile Application Format (SMAF) for multimedia files that can be played on hand-held devices.
mny	00 01 00 00 4D 53 49 53 41 4D 20 44 61 74 61 62 61 73 65	Microsoft Money file
MOV	00 00 0F
MOV	00 00 77
mov	6D 6F 6F 76	Quicktime
mov	6D 64 61 74	QuickTime Movie
mp	0C ED	Monochrome Picture TIFF bitmap file (unconfirmed)
MP3	49 44 33	MPEG-1 Audio Layer 3 (MP3) audio file
MP3	FF FB 50
mp4	00 00 00 18 66 74 79 70 33 67 70 35	MPEG-4 video files
MPA	00 00 01
mpg; mpeg	00 00 01 B3	MPEG Movie
mpg	00 00 01 BA	MPEG
MSC	3C 3F 78
msc	3C 3F 78 6D 6C 20 76 65 72 73 69 6F 6E 3D 22 31 2E 30 22 3F 3E 0D 0A 3C 4D 4D 43 5F 43 6F 6E 73 6F 6C 65 46 69 6C 65 20 43 6F 6E 73 6F 6C 65 56 65 72 73 69 6F 6E 3D 22	Microsoft Management Console Snap-in Control file
msi	23 20	Cerius2 file
MSV	4D 53 5F 56 4F 49 43 45	Sony Memory Stick Compressed Voice file
NES	4E 45 53
NLS	C2 20 20
nri	0E 4E 65 72 6F 49 53 4F	Nero CD Compilation
ntf	1A 00 00	Lotus Notes database template
nsf; ntf	1A 00 00 03 00 00	Lotus Notes Database/Template
nsf	1A 00 00 03 00 00 11 00	Notes Database
nsf	1A 00 00 04 00 00	Lotus Notes database
ntf	30 31 4F 52 44 4E 41 4E 43 45 20 53 55 52 56 45 59 20 20 20 20 20 20 20	National Transfer Format Map File
obj	4C 01	Microsoft Common Object File Format (COFF) relocatable object code file for an Intel 386 or later/compatible processors
OCX	4D 5A	ActiveX or OLE Custom Control
OCX	4D 5A 90
OLB	4D 5A	OLE object library
OLB	4D 5A 90
org; pfc	41 4F 4C 56 4D 31 30 30	AOL personal file cabinet (PFC) file
pak	1A 0B	Compressed archive file
PAT	47 46 31 50 41 54 43 48	Advanced Gravis Ultrasound patch file
PAT	47 50 41 54	GIMP (GNU Image Manipulation Program) pattern file
PBK	5B 41 44
PCB	17 A1 50
PCS	0A 05 01
pcx	0A nn 01 01	ZSOFT Paintbrush file(where nn = 0x02, 0x03, or 0x05)
pcx	0A 05 01 08	PC Paintbrush(often associated with Quake Engine games)
pdb	[11 byte offset] 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00	Palmpilot Database/Document File
PDF	25 50 44
pdf; fdf	25 50 44 46	Adobe Portable Document Format and Forms Document file
pdf	25 50 44 46 2D 31 2E	Adobe Acrobat
PDG	48 48 02
pf	11 00 00 00 53 43 43 41	Windows prefetch file
pic	01 00 00 00 01	Unknown type picture file
PJT	00 00 07
PLL	24 53 6F
PNG	89 50 4E
PNG	89 50 4E 47
png	89 50 4E 47 0D 0A	PNG Image File
png	89 50 4E 47 0D 0A 1A 0A	PNG Image File
PPC	52 65 63
PPT	D0 CF 11
ppt	[512 byte offset] 00 6E 1E F0	PowerPoint presentation subheader (MS Office)
ppt	[512 byte offset] 0F 00 E8 03	PowerPoint presentation subheader (MS Office)
PPZ	4D 53 43 46	Powerpoint Packaged Presentation
prc	42 4F 4F 4B 4D 4F 42 49	Palmpilot resource file
PRG	23 44 45
ps	25 21 50 53 2D 41 64 6F 62 65	Postscript
PSD	38 42 50
psd	38 42 50 53	Adobe Photoshop image file
psp	7E 42 4B 00	PaintShop Pro Image File
pst	21 42 44 4E	Microsoft Outlook Personal Folder file
pwl	E3 82 85 96	Windows Password
qbb	45 86 00 00 06 00	Intuit QuickBooks Backup file
qdf	AC 9E BD 8F	Quicken
qph	03 00 00 00	Quicken price history file
qt	6D 64 61 74	Quicktime Movie File
qxd	00 00 4D 4D 58 50 52
ra	2E 52 4D 46 00 00 00 12 00	Real Audio file
ra; ram	2E 72 61 FD	Real Audio File
ra	2E 72 61 FD 00	RealAudio streaming media file
RAR	52 61 72
rar	52 61 72 21	RAR Archive File
RAW	06 05 00
reg	52 45 47 45 44 49 54 34
rgb	01 DA 01 01 00 03	Silicon Graphics RGB Bitmap
RM	2E 52 4D
rm; rmvb	2E 52 4D 46	Real Media streaming media file
rpm	ED AB EE DB	RPM Archive File
RTD	43 23 2B 44 A4 43 4D A5 48 64 72	RagTime document file
RTF	7B 5C 72
rtf	7B 5C 72 74 66	Rich Text Format File
sav	24 46 4C 32 40 28 23 29 20 53 50 53 53 20 44 41 54 41 20 46 49 4C 45	SPSS Data file
SBV	46 45 44 46	(Unknown file type)
SCH	2A 76 65
scm	80 53 43
SH3	48 48 47 42 31	Harvard Graphics presentation file
SHD	4B 49 00 00	Windows 9x printer spool file
sit	53 49 54 21	Stuffit v1 Archive File
sit	53 74 75 66 66 49 74	Stuffit v5 Archive File
sle	3A 56 45 52 53 49 4F 4E	Surfplan kite project file
sle	41 43 76	teganos Security Suite virtual secure drive
sly; srt; slt	53 52 01 00	Sage sly.or.srt.or.slt
SMD	00 FF FF
snm	00 1E 84 90 00 00 00 00	Netscape Communicator (v4) mail folder
SNP	4D 53 43 46	Microsoft Access Snapshot Viewer file
sol	00 BF	Adobe Flash shared object file (e.g., Flash cookies)
spl	00 00 01 00	Windows NT/2000/XP printer spool file
SCR	4D 5A	Screen saver
SUB	FF FF FF
SWF	43 57 53	Shockwave Flash file (v5+)
SWF	46 57 53	Macromedia Shockwave Flash player file
sxc	calc	OpenOffice Calc
sxd	draw	OpenOffice Draw
sxi	impress	OpenOffice Impress
sxm	math	OpenOffice Math
sxw	writer	OpenOffice Writer
syw	41 4D 59 4F	Harvard Graphics symbol graphic
TAG	00 00 02
tar; cpio	30 37 30 37 30 37	CPIO Archive File
tar.z	1F 9D 90	Compressed tape archive file
tga	00 00 10 00 00	RLE压缩的前5字节
TGA	00 00 02
tga	00 00 02 00 00	未压缩的前5字节
TIF; TIFF	49 20 49	Tagged Image File Format file
tif; tiff	49 49 2A	TIFF (Intel)
tif; tiff	49 49 2A 00	Tagged Image File Format file (little endian, i.e., LSB first in the byte; Intel)
TIF; TIFF	4D 4D 00 2A	Tagged Image File Format file (big endian, i.e., LSB last in the byte; Motorola)
tif; tiff	4D 4D 2A	TIFF (Motorola)
TIF; TIFF	4D 4D 00 2B	BigTIFF files; Tagged Image File Format files >4 GB
TLB	4D 53 46 54 02 00 01 00	OLE, SPSS, or Visual C++ type library file
tr1	01 10	Novell LANalyzer capture file
TST	00 01 00
TTF	00 01 00
ufa	55 46 41	UFA Archive File
VBX	4D 5A	VisualBASIC application
VCD	45 4E 54 52 59 56 43 44 02 00 00 01 02 00 18 58	VideoVCD (GNU VCDImager) file
vcf	42 45 47 49 4E 3A 56 43 41 52 44 0D 0A	vCard file
vob	00 00 01 BA	DVD Video Movie File (video/dvd, video/mpeg)
VXD, 386	4D 5A	Windows virtual device drivers
WAV	52 49 46
wav	57 41 56 45	Wave
wav	57 41 56 45 66 6D 74	Wave Files
wb2	00 00 02 00	QuattroPro for Windows Spreadsheet file
wb3	[24 byte offset] 3E 00 03 00 FE FF 09 00 06	Quatro Pro for Windows 7.0 Notebook file
wk1; wks	20 00 60 40 60	Lotus 123 v1 Worksheet
wk1	00 00 02 00 06 04 06 00 08 00 00 00 00 00	Lotus 1-2-3 spreadsheet (v1) file
wk3	00 00 1A 00 00 10 04 00	Lotus 123 spreadsheet (v3) file
wk4; wk5	00 00 1A 00 02 10 04 00	Lotus 1-2-3 spreadsheet (v4, v5) file
wks	0E 57 4B 53	DeskMate Worksheet
WMA	30 26 B2
wmf	01 00 09 00	Graphics Metafile
wmf	01 00 09 00 00 03	Windows Metadata file (Win 3.x format)
wmf	02 00 09 00	Graphics Metafile
wmf	D7 CD C6 9A	Windows Meta File
WMV	30 26 B2
wp	FF 57 50 43	WordPerfect v5 or v6
wpd	FF 57 50 43	WordPerfect
wpg	FF 57 50 47	WordPerfect Graphics
wri	31 BE	Microsoft Write file
WRI	31 BE 00
wri	32 BE	Microsoft Write file
ws	1D 7D	WordStar Version 5.0/6.0 document
XBE	58 42 45
xdr	3C	BizTalk XML-Data Reduced Schema file
xls	09 02 06 00 00 00 10 00 B9 04 5C 00	MS Excel v2
xls	09 04 06 00 00 00 10 00 F6 05 5C 00	MS Excel v4
XLS	D0 CF 11
xls	D0 CF 11 E0	MS Excel
xls	[512 byte offset] 09 08 10 00 00 06 05 00	Excel spreadsheet subheader (MS Office)
XML	3C 3F 78
xml	3C 3F 78 6D 6C	XML Document
xml	FF FE 3C 00 52 00 4F 00 4F 00 54 00 53 00 54 00 55 00 42 00	XML Document (ROOTSTUB)
XMV	00 50 01
XSL	FF FE 3C
xul	72 73 69 6F 6E 3D 22 31 3C 3F 78 6D 6C 20 76 65 2E 30 22 3F 3E	XML User Interface Language file
z	1F 9D	TAR Compressed Archive File
Z	1F 9D 8C
ZIP	50 4B 03
zip; jar; zipx	50 4B 03 04	ZIP Archive
zip	50 4B 30 30	ZIP Archive (outdated)
Zip	50 4B 30 30 50 4B 03 04	WINZIP Compressed
zoo	5A 4F 4F 20	ZOO Archive File

有了这个表格，我们就可以通过检查文件的十六进制头来判断文件实际的类型了。

方法

windows下

我们可以通过ultraedit之类的文本编辑器检查文件的十六进制表示，很方便。

Linux下

我们有hexdump命令来查看文件的十六进制形式，用这种方法查看png文件的结果大概是这样的：

0000000 5089 474e 0a0d 0a1a 0000 0d00 4849 5244
0000010 0000 dc00 0000 3200 0608 0000 3700 b514
0000020 0073 0000 7009 5948 0073 0b00 0013 0b00
0000030 0113 9a00 189c 0000 4d0a 4369 5043 6850
0000040 746f 736f 6f68 2070 4349 2043 7270 666f
.......

然而，这个只能查看不能修改，而且实际上，他的高低位是反着的，实际上他应该表示为：

1
2

0000000 8050 4e47 0d0a 1a0a 0000 000d 4948 4452
.......

这样才是标准的png文件的头。

当然，我们有更方便强大的vim，用这个可以查看和修改文件的十六进制表示形式。我们用vim打开刚才的png文件，会的到以下的ascii表示形式：

<89>PNG^M                                                                   
^Z
^@^@^@^MIHDR^@^@^@Ü^@^@^@2^H^F^@^@^@7^Tµs^@^@^@ pHYs^@^@^K^S^@^@^K^S^A^@<9a>    <9c>^X^@^@
MiCCPPhotoshop ICC profile^@^@xÚ<9d>SwX<93>÷^V>ß÷e^OVBØð±<97>l<81>^@"#¬^HÈ^P Y¢^P<92>^@a<84>^P^R@Å<85><88>
V^T^U^Q<9c>HUÄ<82>Õ
H<9d><88>â (¸gA<8a><88>Z<8b>U\8î^_Ü§µ}zïííû×û¼ç<9c>çüÎyÏ^O<80>^Q^R&<91>æ¢j^@ 9R<85><:Ø^_<8f>OHÄÉ½<80>^B^UHà^D ^PæËÂg^EÅ^@^@ð^Cyx~t°?ü^A¯o^@^B^@pÕ.$^RÇáÿ< 83>ºP&W^@ <91>^@à"^Rç^K^A<90>R^@È.TÈ^T^@È^X^@°S³d
^@<94>^@^@ly|B"^@ª^M^@ìôI>^E^@Ø©<93>Ü^W^@Ø¢^\©^H^@<8d>^A^@<99>(G$^B@»^@`U<81 >R,^BÀÂ^@ ¬@".^DÀ®^A<80>Y¶2G^B<80>½^E^@v<8e>X<90>^O@`^@<80><99>B,Ì^@ 8^B^@C^ ^^SÍ^C L^C 0Ò¿à©_p<85>¸H^A^@ÀË<95>Í<97>KÒ3^T¸<95>Ð^Zwòðàâ!âÂl±Ba^W)^Pf ä"<9
..........

接下来我们需要在命令模式下输入 :%!xxd 这样会得到以下的样子：

0000000: 8950 4e47 0d0a 1a0a 0000 000d 4948 4452  .PNG........IHDR   
0000010: 0000 00dc 0000 0032 0806 0000 0037 14b5  .......2.....7..
0000020: 7300 0000 0970 4859 7300 000b 1300 000b  s....pHYs.......
0000030: 1301 009a 9c18 0000 0a4d 6943 4350 5068 .........MiCCPPh
0000040: 6f74 6f73 686f 7020 4943 4320 7072 6f66 otoshop ICC prof
0000050: 696c 6500 0078 da9d 5377 5893 f716 3edf ile..x..SwX...>.
0000060: f765 0f56 42d8 f0b1 976c 8100 2223 ac08 .e.VB....l.."#..
0000070: c810 59a2 1092 0061 8410 1240 c585 880a ..Y....a...@....
.......