Use file to determine the type of a file. For example, you receive the file unknown from another user and you want to know sort of file is unknown.
file unknown unknown: JPEG image data, JFIF standard
file returns that unknown is a Jpeg file, you can view jpeg files with xv
Note: file is found at /usr/local/bin/file
About filename extensions.
Filename extensions are the end of a filename following a period. For instance the file hello.ps has the extension ps, commonly used for Postscript Documents. Extensions are used to set the type of a file in Operating Systems such as DOS, Windows and OS/2. UNIX, however, does not care about the extension of a file. A file on hello.ps may return uuencoded text or gzip compressed data. It is important to remember that the extension tells us nothing about the actual contents of the file.
Common File Types and associated Applications
Assumes you have typed:file filename
|ASCII text||Any text editor, examples are:
|ASCII C program text, with CRLF line terminators||gcc
|Bourne shell script text executable||This is a script, type ./filename to run it.|
|ELF 32-bit MSB executable, SPARC, version 1, dynamically linked (uses shared libs), stripped||This is an application, type ./filename to launch it.
(This application will only run on a Sun Server: monaco, fresno, zurich...)
|GIF image data, version 89a, height x width||xv
|gzip compressed data, deflated|
|HTML document text||firefox
|compiled Java class data, version 45.3||java|
|LaTeX 2e document text||latex|
|news or mail text||mail
|Microsoft Office Document||StarOffice, or a Windows Machine|
|MS-DOS executable (EXE), OS/2 or MS Windows||A machine running Windows
Simonyi Hall 028,
Simonyi Hall 114
|PDF document, version 8.1.3||Adobe Acrobat Reader acroread
|perl script text||This is a script, type ./filename to run it.|
|PostScript document text conforming at level 2.0||ghostview
|GNU tar archive
|uuencoded or xxencoded text||uudecode|
|Zip archive data, at least v2.0 to extract||unzip|