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FILE(1)                BSD General Commands Manual                FILE(1)

NAME
     file — determine file type

SYNOPSIS
     file [-bcdEhiklLNnprsSvzZ0] [--apple] [--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 5.38 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).  Excep‐
     tions 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” 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/share/misc/magic.mgc, or the files in the directory
     /usr/share/misc/magic if the compiled file does not exist.  In addi‐
     tion, 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 dif‐
     ferent 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 mis‐
     cellany (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 describing the file type, the lat‐
             ter 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 flag
             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 han‐
             dling 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 set‐
                       ting 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.

             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’.

     --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 file‐
             name 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
             option causes symlinks not to be followed (on systems that
             support symbolic links).  This is the default if the envi‐
             ronment 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 descend‐
             ing by magic(5) strength which is used for the matching (see
             also the -k option).

     -L, --dereference
             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 contain‐
             ing 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
                   indir        15         recursion limit for indirect
                                                                          magic
                   name         30         use count limit for name/use
                                                                          magic
                   elf_notes    256        max ELF notes processed
                   elf_phnum    128        max ELF program sections
                                                                          processed
                   elf_shnum    32768      max ELF sections processed
                   regex        8192       length limit for regex
                                                                          searches
                   bytes        1048576    max number of bytes to read
                                                                          from
                                                                          file

     -r, --raw
             Don't translate unprintable characters to \ooo.  Normally
             file translates unprintable characters to their octal repre‐
             sentation.

     -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 charac‐
             ter 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
             flag disables sandboxing which is enabled by default.  This
             option is needed for file to execute external decompressing
             programs, i.e. when the -z flag is specified and the built-
             in decompressors are not available.  On systems where sand‐
             boxing 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 separa‐
             tor, 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 descrip‐
             tion (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, oth‐
     erwise it does not.  This is also controlled by the -L and -h
     options.

FILES
     /usr/share/misc/magic.mgc  Default compiled list of magic.
     /usr/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 mes‐
     sages, 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

SEE ALSO
     hexdump(1), od(1), strings(1), magic(5)

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 Sys‐
     tem V program of the same name.  This version knows more magic, how‐
     ever, 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 back‐
     slash, 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 decom‐
     press input files running external programs with the -z option.  To
     enable execution of external decompressors, one needs to disable
     sandboxing using the -S flag.

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/share/misc/magic.orig).

HISTORY
     There has been a file command in every UNIX since at least Research
     Version 4 (man page dated November, 1973).  The System V version
     introduced one significant major change: the external list of magic
     types.  This slowed the program down slightly but made it a lot more
     flexible.

     This program, based on the System V version, was written by Ian Dar‐
     win ⟨ian@darwinsys.com⟩ without looking at anybody else's source
     code.

     John Gilmore revised the code extensively, making it better than the
     first version.  Geoff Collyer found several inadequacies and pro‐
     vided some magic file entries.  Contributions of the ‘&’ operator by
     Rob McMahon, ⟨cudcv@warwick.ac.uk⟩, 1989.

     Guy Harris, ⟨guy@netapp.com⟩, made many changes from 1993 to the
     present.

     Primary development and maintenance from 1990 to the present by
     Christos Zoulas ⟨christos@astron.com⟩.

     Altered by Chris Lowth ⟨chris@lowth.com⟩, 2000: handle the -i option
     to output mime type strings, using an alternative magic file and
     internal logic.

     Altered by Eric Fischer ⟨enf@pobox.com⟩, July, 2000, to identify
     character codes and attempt to identify the languages of non-ASCII
     files.

     Altered by Reuben Thomas ⟨rrt@sc3d.org⟩, 2007-2011, to improve MIME
     support, merge MIME and non-MIME magic, support directories as well
     as files of magic, apply many bug fixes, update and fix a lot of
     magic, improve the build system, improve the documentation, and re‐
     write the Python bindings in pure Python.

     The list of contributors to the ‘magic’ directory (magic files) is
     too long to include here.  You know who you are; thank you.  Many
     contributors are listed in the source files.

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 descrip‐
     tions.

     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 buf‐
     fer 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 off‐
     set, but we give up.  It would be better if buffer managements was
     done when the file descriptor is available so move around the file.
     One must be careful though because this has performance (and thus
     security considerations).

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.

BSD                           July 13, 2019                           BSD