416 lines
11 KiB
Groff
416 lines
11 KiB
Groff
.\" $File: libmagic.man,v 1.45 2019/06/08 22:16:24 christos Exp $
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.\"
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.\" Copyright (c) Christos Zoulas 2003, 2018.
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.\" All Rights Reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice immediately at the beginning of the file, without modification,
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.\" this list of conditions, and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
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.\" ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.Dd June 8, 2019
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.Dt LIBMAGIC 3
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.Os
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.Sh NAME
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.Nm magic_open ,
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.Nm magic_close ,
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.Nm magic_error ,
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.Nm magic_errno ,
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.Nm magic_descriptor ,
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.Nm magic_buffer ,
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.Nm magic_getflags ,
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.Nm magic_setflags ,
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.Nm magic_check ,
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.Nm magic_compile ,
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.Nm magic_list ,
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.Nm magic_load ,
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.Nm magic_load_buffers ,
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.Nm magic_setparam ,
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.Nm magic_getparam ,
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.Nm magic_version
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.Nd Magic number recognition library
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.Sh LIBRARY
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.Lb libmagic
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.Sh SYNOPSIS
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.In magic.h
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.Ft magic_t
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.Fn magic_open "int flags"
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.Ft void
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.Fn magic_close "magic_t cookie"
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.Ft const char *
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.Fn magic_error "magic_t cookie"
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.Ft int
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.Fn magic_errno "magic_t cookie"
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.Ft const char *
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.Fn magic_descriptor "magic_t cookie" "int fd"
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.Ft const char *
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.Fn magic_file "magic_t cookie" "const char *filename"
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.Ft const char *
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.Fn magic_buffer "magic_t cookie" "const void *buffer" "size_t length"
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.Ft int
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.Fn magic_getflags "magic_t cookie"
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.Ft int
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.Fn magic_setflags "magic_t cookie" "int flags"
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.Ft int
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.Fn magic_check "magic_t cookie" "const char *filename"
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.Ft int
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.Fn magic_compile "magic_t cookie" "const char *filename"
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.Ft int
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.Fn magic_list "magic_t cookie" "const char *filename"
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.Ft int
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.Fn magic_load "magic_t cookie" "const char *filename"
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.Ft int
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.Fn magic_load_buffers "magic_t cookie" "void **buffers" "size_t *sizes" "size_t nbuffers"
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.Ft int
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.Fn magic_getparam "magic_t cookie" "int param" "void *value"
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.Ft int
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.Fn magic_setparam "magic_t cookie" "int param" "const void *value"
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.Ft int
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.Fn magic_version "void"
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.Sh DESCRIPTION
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These functions
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operate on the magic database file
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which is described
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in
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.Xr magic __FSECTION__ .
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.Pp
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The function
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.Fn magic_open
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creates a magic cookie pointer and returns it.
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It returns
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.Dv NULL
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if there was an error allocating the magic cookie.
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The
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.Ar flags
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argument specifies how the other magic functions should behave:
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.Bl -tag -width MAGIC_COMPRESS
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.It Dv MAGIC_NONE
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No special handling.
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.It Dv MAGIC_DEBUG
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Print debugging messages to stderr.
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.It Dv MAGIC_SYMLINK
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If the file queried is a symlink, follow it.
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.It Dv MAGIC_COMPRESS
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If the file is compressed, unpack it and look at the contents.
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.It Dv MAGIC_DEVICES
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If the file is a block or character special device, then open the device
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and try to look in its contents.
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.It Dv MAGIC_MIME_TYPE
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Return a MIME type string, instead of a textual description.
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.It Dv MAGIC_MIME_ENCODING
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Return a MIME encoding, instead of a textual description.
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.It Dv MAGIC_MIME
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A shorthand for MAGIC_MIME_TYPE | MAGIC_MIME_ENCODING.
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.It Dv MAGIC_CONTINUE
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Return all matches, not just the first.
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.It Dv MAGIC_CHECK
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Check the magic database for consistency and print warnings to stderr.
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.It Dv MAGIC_PRESERVE_ATIME
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On systems that support
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.Xr utime 3
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or
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.Xr utimes 2 ,
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attempt to preserve the access time of files analysed.
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.It Dv MAGIC_RAW
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Don't translate unprintable characters to a \eooo octal representation.
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.It Dv MAGIC_ERROR
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Treat operating system errors while trying to open files and follow symlinks
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as real errors, instead of printing them in the magic buffer.
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.It Dv MAGIC_APPLE
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Return the Apple creator and type.
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.It Dv MAGIC_EXTENSION
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Return a slash-separated list of extensions for this file type.
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.It Dv MAGIC_COMPRESS_TRANSP
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Don't report on compression, only report about the uncompressed data.
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.It Dv MAGIC_NO_CHECK_APPTYPE
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Don't check for
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.Dv EMX
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application type (only on EMX).
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.It Dv MAGIC_NO_CHECK_CDF
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Don't get extra information on MS Composite Document Files.
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.It Dv MAGIC_NO_CHECK_COMPRESS
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Don't look inside compressed files.
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.It Dv MAGIC_NO_CHECK_ELF
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Don't print ELF details.
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.It Dv MAGIC_NO_CHECK_ENCODING
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Don't check text encodings.
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.It Dv MAGIC_NO_CHECK_SOFT
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Don't consult magic files.
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.It Dv MAGIC_NO_CHECK_TAR
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Don't examine tar files.
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.It Dv MAGIC_NO_CHECK_TEXT
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Don't check for various types of text files.
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.It Dv MAGIC_NO_CHECK_TOKENS
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Don't look for known tokens inside ascii files.
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.It Dv MAGIC_NO_CHECK_JSON
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Don't examine JSON files.
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.It Dv MAGIC_NO_CHECK_CSV
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Don't examine CSV files.
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.El
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.Pp
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The
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.Fn magic_close
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function closes the
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.Xr magic __FSECTION__
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database and deallocates any resources used.
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.Pp
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The
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.Fn magic_error
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function returns a textual explanation of the last error, or
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.Dv NULL
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if there was no error.
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.Pp
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The
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.Fn magic_errno
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function returns the last operating system error number
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.Pq Xr errno 2
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that was encountered by a system call.
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.Pp
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The
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.Fn magic_file
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function returns a textual description of the contents of the
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.Ar filename
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argument, or
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.Dv NULL
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if an error occurred.
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If the
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.Ar filename
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is
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.Dv NULL ,
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then stdin is used.
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.Pp
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The
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.Fn magic_descriptor
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function returns a textual description of the contents of the
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.Ar fd
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argument, or
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.Dv NULL
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if an error occurred.
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.Pp
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The
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.Fn magic_buffer
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function returns a textual description of the contents of the
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.Ar buffer
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argument with
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.Ar length
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bytes size.
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.Pp
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The
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.Fn magic_getflags
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functions returns a value representing current
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.Ar flags
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set.
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.Pp
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The
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.Fn magic_setflags
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function sets the
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.Ar flags
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described above.
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Note that using both MIME flags together can also
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return extra information on the charset.
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.Pp
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The
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.Fn magic_check
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function can be used to check the validity of entries in the colon
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separated database files passed in as
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.Ar filename ,
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or
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.Dv NULL
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for the default database.
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It returns 0 on success and \-1 on failure.
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.Pp
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The
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.Fn magic_compile
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function can be used to compile the colon
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separated list of database files passed in as
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.Ar filename ,
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or
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.Dv NULL
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for the default database.
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It returns 0 on success and \-1 on failure.
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The compiled files created are named from the
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.Xr basename 1
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of each file argument with
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.Dq .mgc
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appended to it.
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.Pp
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The
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.Fn magic_list
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function dumps all magic entries in a human readable format,
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dumping first the entries that are matched against binary files and then the
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ones that match text files.
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It takes and optional
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.Fa filename
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argument which is a colon separated list of database files, or
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.Dv NULL
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for the default database.
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.Pp
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The
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.Fn magic_load
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function must be used to load the colon
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separated list of database files passed in as
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.Ar filename ,
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or
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.Dv NULL
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for the default database file before any magic queries can performed.
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.Pp
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The default database file is named by the MAGIC environment variable.
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If that variable is not set, the default database file name is __MAGIC__.
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.Fn magic_load
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adds
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.Dq .mgc
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to the database filename as appropriate.
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.Pp
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The
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.Fn magic_load_buffers
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function takes an array of size
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.Fa nbuffers
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of
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.Fa buffers
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with a respective size for each in the array of
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.Fa sizes
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loaded with the contents of the magic databases from the filesystem.
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This function can be used in environment where the magic library does
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not have direct access to the filesystem, but can access the magic
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database via shared memory or other IPC means.
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.Pp
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The
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.Fn magic_getparam
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and
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.Fn magic_setparam
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allow getting and setting various limits related to the magic
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library.
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.Bl -column "MAGIC_PARAM_ELF_PHNUM_MAX" "size_t" "Default" -offset indent
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.It Sy "Parameter" Ta Sy "Type" Ta Sy "Default"
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.It Li MAGIC_PARAM_INDIR_MAX Ta size_t Ta 15
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.It Li MAGIC_PARAM_NAME_MAX Ta size_t Ta 30
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.It Li MAGIC_PARAM_ELF_NOTES_MAX Ta size_t Ta 256
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.It Li MAGIC_PARAM_ELF_PHNUM_MAX Ta size_t Ta 128
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.It Li MAGIC_PARAM_ELF_SHNUM_MAX Ta size_t Ta 32768
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.It Li MAGIC_PARAM_REGEX_MAX Ta size_t Ta 8192
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.It Li MAGIC_PARAM_BYTES_MAX Ta size_t Ta 1048576
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.El
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.Pp
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The
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.Dv MAGIC_PARAM_INDIR_RECURSION
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parameter controls how many levels of recursion will be followed for
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indirect magic entries.
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.Pp
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The
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.Dv MAGIC_PARAM_NAME_RECURSION
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parameter controls how many levels of recursion will be followed for
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for name/use calls.
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.Pp
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The
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.Dv MAGIC_PARAM_NAME_MAX
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parameter controls the maximum number of calls for name/use.
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.Pp
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The
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.Dv MAGIC_PARAM_NOTES_MAX
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parameter controls how many ELF notes will be processed.
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.Pp
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The
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.Dv MAGIC_PARAM_PHNUM_MAX
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parameter controls how many ELF program sections will be processed.
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.Pp
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The
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.Dv MAGIC_PARAM_SHNUM_MAX
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parameter controls how many ELF sections will be processed.
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.Pp
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The
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.Fn magic_version
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command returns the version number of this library which is compiled into
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the shared library using the constant
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.Dv MAGIC_VERSION
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from
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.In magic.h .
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This can be used by client programs to verify that the version they compile
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against is the same as the version that they run against.
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.Sh RETURN VALUES
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The function
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.Fn magic_open
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returns a magic cookie on success and
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.Dv NULL
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on failure setting errno to an appropriate value.
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It will set errno to
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.Er EINVAL
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if an unsupported value for flags was given.
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The
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.Fn magic_list ,
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.Fn magic_load ,
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.Fn magic_compile ,
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and
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.Fn magic_check
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functions return 0 on success and \-1 on failure.
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The
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.Fn magic_buffer ,
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.Fn magic_getpath ,
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and
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.Fn magic_file ,
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functions return a string on success and
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.Dv NULL
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on failure.
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The
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.Fn magic_error
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function returns a textual description of the errors of the above
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functions, or
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.Dv NULL
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if there was no error.
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The
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.Fn magic_version
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always returns the version number of the library.
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Finally,
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.Fn magic_setflags
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returns \-1 on systems that don't support
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.Xr utime 3 ,
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or
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.Xr utimes 2
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when
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.Dv MAGIC_PRESERVE_ATIME
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is set.
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.Sh FILES
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.Bl -tag -width __MAGIC__.mgc -compact
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.It Pa __MAGIC__
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The non-compiled default magic database.
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.It Pa __MAGIC__.mgc
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The compiled default magic database.
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.El
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.Sh SEE ALSO
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.Xr file __CSECTION__ ,
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.Xr magic __FSECTION__
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.Sh BUGS
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The results from
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.Fn magic_buffer
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and
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.Fn magic_file
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where the buffer and the file contain the same data
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can produce different results, because in the
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.Fn magic_file
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case, the program can
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.Xr lseek 2
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and
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.Xr stat 2
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the file descriptor.
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.Sh AUTHORS
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.An M\(oans Rullg\(oard
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Initial libmagic implementation, and configuration.
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.An Christos Zoulas
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API cleanup, error code and allocation handling.
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