# file

## NAME



           **file** — determine file type
    


## SYNOPSIS



           **file**[**-bcdEhiklLNnprsSvzZ0**] [**--apple**] [**--exclude-quiet**]
           [**--extension**] [**--mime-encoding**] [**--mime-type**] [**-e** _testname_]
           [**-F** _separator_] [**-f** _namefile_] [**-m** _magicfiles_] [**-P** _name=value_]
           _file ..._ **file -C**[**-m** _magicfiles_] **file**[**--help**]
    


## DESCRIPTION



           This manual page documents version 5.46 of the **file** command.
    
           **file** tests each argument in an attempt to classify it.  There are
           three sets of tests, performed in this order: filesystem tests,
           magic tests, and language tests.  The _first_ test that succeeds
           causes the file type to be printed.
    
           The type printed will usually contain one of the words _text_ (the
           file contains only printing characters and a few common control
           characters and is probably safe to read on an ASCII terminal),
           _executable_ (the file contains the result of compiling a program in
           a form understandable to some UNIX kernel or another), or _data_
           meaning anything else (data is usually “binary” or non-printable).
           Exceptions are well-known file formats (core files, tar archives)
           that are known to contain binary data.  When modifying magic files
           or the program itself, make sure to _preserve these keywords_.
           Users depend on knowing that all the readable files in a directory
           have the word “text” printed.  Don't do as Berkeley did and change
           “shell commands text” to “shell script”.
    
           The filesystem tests are based on examining the return from a
           _stat_(2) system call.  The program checks to see if the file is
           empty, or if it's some sort of special file.  Any known file types
           appropriate to the system you are running on (sockets, symbolic
           links, or named pipes (FIFOs) on those systems that implement
           them) are intuited if they are defined in the system header file
           <_sys/stat.h_ >.
    
           The magic tests are used to check for files with data in
           particular fixed formats.  The canonical example of this is a
           binary executable (compiled program) a.out file, whose format is
           defined in <_elf.h_ >, <_a.out.h_ > and possibly <_exec.h_ > in the
           standard include directory.  These files have a “magic number”
           stored in a particular place near the beginning of the file that
           tells the UNIX operating system that the file is a binary
           executable, and which of several types thereof.  The concept of a
           “magic number” has been applied by extension to data files.  Any
           file with some invariant identifier at a small fixed offset into
           the file can usually be described in this way.  The information
           identifying these files is read from the compiled magic file
           _/usr/local/share/misc/magic.mgc_ , or the files in the directory
           _/usr/local/share/misc/magic_ if the compiled file does not exist.
           In addition, if _$HOME/.magic.mgc_ or _$HOME/.magic_ exists, it will
           be used in preference to the system magic files.
    
           If a file does not match any of the entries in the magic file, it
           is examined to see if it seems to be a text file.  ASCII,
           ISO-8859-x, non-ISO 8-bit extended-ASCII character sets (such as
           those used on Macintosh and IBM PC systems), UTF-8-encoded
           Unicode, UTF-16-encoded Unicode, and EBCDIC character sets can be
           distinguished by the different ranges and sequences of bytes that
           constitute printable text in each set.  If a file passes any of
           these tests, its character set is reported.  ASCII, ISO-8859-x,
           UTF-8, and extended-ASCII files are identified as “text” because
           they will be mostly readable on nearly any terminal; UTF-16 and
           EBCDIC are only “character data” because, while they contain text,
           it is text that will require translation before it can be read.
           In addition, **file** will attempt to determine other characteristics
           of text-type files.  If the lines of a file are terminated by CR,
           CRLF, or NEL, instead of the Unix-standard LF, this will be
           reported.  Files that contain embedded escape sequences or
           overstriking will also be identified.
    
           Once **file** has determined the character set used in a text-type
           file, it will attempt to determine in what language the file is
           written.  The language tests look for particular strings (cf.
           <_names.h_ >) that can appear anywhere in the first few blocks of a
           file.  For example, the keyword _.br_ indicates that the file is
           most likely a _troff_(1) input file, just as the keyword _struct_
           indicates a C program.  These tests are less reliable than the
           previous two groups, so they are performed last.  The language
           test routines also test for some miscellany (such as _tar_(1)
           archives, JSON files).
    
           Any file that cannot be identified as having been written in any
           of the character sets listed above is simply said to be “data”.
    


## OPTIONS



           **--apple**
                   Causes the **file** command to output the file type and
                   creator code as used by older MacOS versions.  The code
                   consists of eight letters, the first four describing the
                   file type, the latter four the creator.  This option works
                   properly only for file formats that have the apple-style
                   output defined.
    
           **-b** , **--brief**
                   Do not prepend filenames to output lines (brief mode).
    
           **-C** , **--compile**
                   Write a _magic.mgc_ output file that contains a pre-parsed
                   version of the magic file or directory.
    
           **-c** , **--checking-printout**
                   Cause a checking printout of the parsed form of the magic
                   file.  This is usually used in conjunction with the **-m**
                   option to debug a new magic file before installing it.
    
           **-d** Prints internal debugging information to stderr.
    
           **-E** On filesystem errors (file not found etc), instead of
                   handling the error as regular output as POSIX mandates and
                   keep going, issue an error message and exit.
    
           **-e** , **--exclude** _testname_
                   Exclude the test named in _testname_ from the list of tests
                   made to determine the file type.  Valid test names are:
    
                   apptype   EMX application type (only on EMX).
    
                   ascii     Various types of text files (this test will try
                             to guess the text encoding, irrespective of the
                             setting of the ‘encoding’ option).
    
                   encoding  Different text encodings for soft magic tests.
    
                   tokens    Ignored for backwards compatibility.
    
                   cdf       Prints details of Compound Document Files.
    
                   compress  Checks for, and looks inside, compressed files.
    
                   csv       Checks Comma Separated Value files.
    
                   elf       Prints ELF file details, provided soft magic
                             tests are enabled and the elf magic is found.
    
                   json      Examines JSON (RFC-7159) files by parsing them
                             for compliance.
    
                   soft      Consults magic files.
    
                   simh      Examines SIMH tape files.
    
                   tar       Examines tar files by verifying the checksum of
                             the 512 byte tar header.  Excluding this test
                             can provide more detailed content description by
                             using the soft magic method.
    
                   text      A synonym for ‘ascii’.
    
           **--exclude-quiet**
                   Like **--exclude** but ignore tests that **file** does not know
                   about.  This is intended for compatibility with older
                   versions of **file**.
    
           **--extension**
                   Print a slash-separated list of valid extensions for the
                   file type found.
    
           **-F** , **--separator** _separator_
                   Use the specified string as the separator between the
                   filename and the file result returned.  Defaults to ‘:’.
    
           **-f** , **--files-from** _namefile_
                   Read the names of the files to be examined from _namefile_
                   (one per line) before the argument list.  Either _namefile_
                   or at least one filename argument must be present; to test
                   the standard input, use ‘-’ as a filename argument.
                   Please note that _namefile_ is unwrapped and the enclosed
                   filenames are processed when this option is encountered
                   and before any further options processing is done.  This
                   allows one to process multiple lists of files with
                   different command line arguments on the same **file**
                   invocation.  Thus if you want to set the delimiter, you
                   need to do it before you specify the list of files, like:
                   “**-F** _@_ **-f** _namefile_ ”, instead of: “**-f** _namefile_ **-F** _@_ ”.
    
           **-h** , **--no-dereference**
                   This option causes symlinks not to be followed (on systems
                   that support symbolic links).  This is the default if the
                   environment variable POSIXLY_CORRECT is not defined.
    
           **-i** , **--mime**
                   Causes the **file** command to output mime type strings rather
                   than the more traditional human readable ones.  Thus it
                   may say ‘text/plain; charset=us-ascii’ rather than “ASCII
                   text”.
    
           **--mime-type** , **--mime-encoding**
                   Like **-i** , but print only the specified element(s).
    
           **-k** , **--keep-going**
                   Don't stop at the first match, keep going.  Subsequent
                   matches will be have the string ‘\012- ’ prepended.  (If
                   you want a newline, see the **-r** option.)  The magic pattern
                   with the highest strength (see the **-l** option) comes first.
    
           **-l** , **--list**
                   Shows a list of patterns and their strength sorted
                   descending by _magic_(4) strength which is used for the
                   matching (see also the **-k** option).
    
           **-L** , **--dereference**
                   This option causes symlinks to be followed, as the like-
                   named option in _ls_(1) (on systems that support symbolic
                   links).  This is the default if the environment variable
                   POSIXLY_CORRECT is defined.
    
           **-m** , **--magic-file** _magicfiles_
                   Specify an alternate list of files and directories
                   containing magic.  This can be a single item, or a colon-
                   separated list.  If a compiled magic file is found
                   alongside a file or directory, it will be used instead.
    
           **-N** , **--no-pad**
                   Don't pad filenames so that they align in the output.
    
           **-n** , **--no-buffer**
                   Force stdout to be flushed after checking each file.  This
                   is only useful if checking a list of files.  It is
                   intended to be used by programs that want filetype output
                   from a pipe.
    
           **-p** , **--preserve-date**
                   On systems that support _utime_(3) or _utimes_(2), attempt to
                   preserve the access time of files analyzed, to pretend
                   that **file** never read them.
    
           **-P** , **--parameter** _name=value_
                   Set various parameter limits.
    
                   **Name         Default    Explanation**
                   **bytes** 1M         max number of bytes to read from
                                                                                         file
                   **elf_notes** 256        max ELF notes processed
                   **elf_phnum** 2K         max ELF program sections processed
                   **elf_shnum** 32K        max ELF sections processed
                   **elf_shsize** 128MB      max ELF section size processed
                   **encoding** 65K        max number of bytes to determine
                                                                                         encoding
                   **indir** 50         recursion limit for indirect magic
                   **name** 150        use count limit for name/use magic
                   **regex** 8K         length limit for regex searches
    
           **-r** , **--raw**
                   Don't translate unprintable characters to \ooo.  Normally
                   **file** translates unprintable characters to their octal
                   representation.
    
           **-s** , **--special-files**
                   Normally, **file** only attempts to read and determine the
                   type of argument files which _stat_(2) reports are ordinary
                   files.  This prevents problems, because reading special
                   files may have peculiar consequences.  Specifying the **-s**
                   option causes **file** to also read argument files which are
                   block or character special files.  This is useful for
                   determining the filesystem types of the data in raw disk
                   partitions, which are block special files.  This option
                   also causes **file** to disregard the file size as reported by
                   _stat_(2) since on some systems it reports a zero size for
                   raw disk partitions.
    
           **-S** , **--no-sandbox**
                   On systems where libseccomp
                   (_https://github.com/seccomp/libseccomp _) is available, the
                   **-S** option disables sandboxing which is enabled by default.
                   This option is needed for **file** to execute external
                   decompressing programs, i.e. when the **-z** option is
                   specified and the built-in decompressors are not
                   available.  On systems where sandboxing is not available,
                   this option has no effect.
    
           **-v** , **--version**
                   Print the version of the program and exit.
    
           **-z** , **--uncompress**
                   Try to look inside compressed files.
    
           **-Z** , **--uncompress-noreport**
                   Try to look inside compressed files, but report
                   information about the contents only not the compression.
    
           **-0** , **--print0**
                   Output a null character ‘\0’ after the end of the
                   filename.  Nice to _cut_(1) the output.  This does not
                   affect the separator, which is still printed.
    
                   If this option is repeated more than once, then **file**
                   prints just the filename followed by a NUL followed by the
                   description (or ERROR: text) followed by a second NUL for
                   each entry.
    
           **--help** Print a help message and exit.
    


## ENVIRONMENT



           The environment variable MAGIC can be used to set the default
           magic file name.  If that variable is set, then **file** will not
           attempt to open _$HOME/.magic_.  **file** adds “ _.mgc_ ” to the value of
           this variable as appropriate.  The environment variable
           POSIXLY_CORRECT controls (on systems that support symbolic links),
           whether **file** will attempt to follow symlinks or not.  If set, then
           **file** follows symlink, otherwise it does not.  This is also
           controlled by the **-L** and **-h** options.
    


## FILES



           _/usr/local/share/misc/magic.mgc_  Default compiled list of magic.
           _/usr/local/share/misc/magic_      Directory containing default
                                            magic files.
    


## EXIT STATUS



           **file** will exit with 0 if the operation was successful or >0 if an
           error was encountered.  The following errors cause diagnostic
           messages, but don't affect the program exit code (as POSIX
           requires), unless **-E** is specified:
                 **•** A file cannot be found
                 **•** There is no permission to read a file
                 **•** The file type cannot be determined
    


## EXAMPLES



                 $ file file.c file /dev/{wd0a,hda}
                 file.c:   C program text
                 file:     ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV),
                           dynamically linked (uses shared libs), stripped
                 /dev/wd0a: block special (0/0)
                 /dev/hda: block special (3/0)
    
                 $ file -s /dev/wd0{b,d}
                 /dev/wd0b: data
                 /dev/wd0d: x86 boot sector
    
                 $ file -s /dev/hda{,1,2,3,4,5,6,7,8,9,10}
                 /dev/hda:   x86 boot sector
                 /dev/hda1:  Linux/i386 ext2 filesystem
                 /dev/hda2:  x86 boot sector
                 /dev/hda3:  x86 boot sector, extended partition table
                 /dev/hda4:  Linux/i386 ext2 filesystem
                 /dev/hda5:  Linux/i386 swap file
                 /dev/hda6:  Linux/i386 swap file
                 /dev/hda7:  Linux/i386 swap file
                 /dev/hda8:  Linux/i386 swap file
                 /dev/hda9:  empty
                 /dev/hda10: empty
    
                 $ file -i file.c file /dev/{wd0a,hda}
                 file.c:      text/x-c
                 file:        application/x-executable
                 /dev/hda:    application/x-not-regular-file
                 /dev/wd0a:   application/x-not-regular-file
    


## STANDARDS CONFORMANCE



           This program is believed to exceed the System V Interface
           Definition of FILE(CMD), as near as one can determine from the
           vague language contained therein.  Its behavior is mostly
           compatible with the System V program of the same name.  This
           version knows more magic, however, so it will produce different
           (albeit more accurate) output in many cases.
    
           The one significant difference between this version and System V
           is that this version treats any white space as a delimiter, so
           that spaces in pattern strings must be escaped.  For example,
    
                 >10     string  language impress        (imPRESS data)
    
           in an existing magic file would have to be changed to
    
                 >10     string  language\ impress       (imPRESS data)
    
           In addition, in this version, if a pattern string contains a
           backslash, it must be escaped.  For example
    
                 0       string          \begindata      Andrew Toolkit document
    
           in an existing magic file would have to be changed to
    
                 0       string          \\begindata     Andrew Toolkit document
    
           SunOS releases 3.2 and later from Sun Microsystems include a **file**
           command derived from the System V one, but with some extensions.
           This version differs from Sun's only in minor ways.  It includes
           the extension of the ‘&’ operator, used as, for example,
    
                 >16     long&0x7fffffff >0              not stripped
    


## SECURITY



           On systems where libseccomp
           (_https://github.com/seccomp/libseccomp _) is available, **file** is
           enforces limiting system calls to only the ones necessary for the
           operation of the program.  This enforcement does not provide any
           security benefit when **file** is asked to decompress input files
           running external programs with the **-z** option.  To enable execution
           of external decompressors, one needs to disable sandboxing using
           the **-S** option.
    


## MAGIC DIRECTORY



           The magic file entries have been collected from various sources,
           mainly USENET, and contributed by various authors.  Christos
           Zoulas (address below) will collect additional or corrected magic
           file entries.  A consolidation of magic file entries will be
           distributed periodically.
    
           The order of entries in the magic file is significant.  Depending
           on what system you are using, the order that they are put together
           may be incorrect.  If your old **file** command uses a magic file,
           keep the old magic file around for comparison purposes (rename it
           to _/usr/local/share/misc/magic.orig_).
    


## LEGAL NOTICE



           Copyright (c) Ian F. Darwin, Toronto, Canada, 1986-1999.  Covered
           by the standard Berkeley Software Distribution copyright; see the
           file COPYING in the source distribution.
    
           The files _tar.h_ and _is_tar.c_ were written by John Gilmore from his
           public-domain _tar_(1) program, and are not covered by the above
           license.
    


## BUGS



           Please report bugs and send patches to the bug tracker at
           _https://bugs.astron.com/ _ or the mailing list at ⟨file@astron.com⟩
           (visit _https://mailman.astron.com/mailman/listinfo/file _ first to
           subscribe).
    


## TODO



           Fix output so that tests for MIME and APPLE flags are not needed
           all over the place, and actual output is only done in one place.
           This needs a design.  Suggestion: push possible outputs on to a
           list, then pick the last-pushed (most specific, one hopes) value
           at the end, or use a default if the list is empty.  This should
           not slow down evaluation.
    
           The handling of MAGIC_CONTINUE and printing \012- between entries
           is clumsy and complicated; refactor and centralize.
    
           Some of the encoding logic is hard-coded in encoding.c and can be
           moved to the magic files if we had a !:charset annotation.
    
           Continue to squash all magic bugs.  See Debian BTS for a good
           source.
    
           Store arbitrarily long strings, for example for %s patterns, so
           that they can be printed out.  Fixes Debian bug #271672.  This can
           be done by allocating strings in a string pool, storing the string
           pool at the end of the magic file and converting all the string
           pointers to relative offsets from the string pool.
    
           Add syntax for relative offsets after current level (Debian bug
           #466037).
    
           Make file -ki work, i.e. give multiple MIME types.
    
           Add a zip library so we can peek inside Office2007 documents to
           print more details about their contents.
    
           Add an option to print URLs for the sources of the file
           descriptions.
    
           Combine script searches and add a way to map executable names to
           MIME types (e.g. have a magic value for !:mime which causes the
           resulting string to be looked up in a table).  This would avoid
           adding the same magic repeatedly for each new hash-bang
           interpreter.
    
           When a file descriptor is available, we can skip and adjust the
           buffer instead of the hacky buffer management we do now.
    
           Fix “name” and “use” to check for consistency at compile time
           (duplicate “name”, “use” pointing to undefined “name” ).  Make
           “name” / “use” more efficient by keeping a sorted list of names.
           Special-case ^ to flip endianness in the parser so that it does
           not have to be escaped, and document it.
    
           If the offsets specified internally in the file exceed the buffer
           size ( HOWMANY variable in file.h), then we don't seek to that
           offset, but we give up.  It would be better if buffer managements
           was done when the file descriptor is available so we can seek
           around the file.  One must be careful though because this has
           performance and thus security considerations, because one can slow
           down things by repeatedly seeking.
    
           There is support now for keeping separate buffers and having
           offsets from the end of the file, but the internal buffer
           management still needs an overhaul.
    


## AVAILABILITY



           You can obtain the original author's latest version by anonymous
           FTP on _ftp.astron.com_ in the directory _/pub/file/file-X.YZ.tar.gz_.
    


* * *