add a manual page for the library functions.

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+.\"
+.\" Copyright (c) Christos Zoulas 2003.
+.\" All Rights Reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice immediately at the beginning of the file, without modification,
+.\"    this list of conditions, and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
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+.\"    documentation and/or other materials provided with the distribution.
+.\" 3. The name of the author may not be used to endorse or promote products
+.\"    derived from this software without specific prior written permission.
+.\" 
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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+.\"
+.Dd March 22, 2003
+.Dt MAGIC 3
+.Os
+.Sh NAME
+.Nm magic_open ,
+.Nm magic_close ,
+.Nm magic_error ,
+.Nm magic_file ,
+.Nm magic_buffer ,
+.Nm magic_setflags ,
+.Nm magic_check ,
+.Nm magic_compile ,
+.Nm magic_load
+.Nd Magic number recognition library.
+.Sh LIBRARY
+.Lb libmagic
+.Sh SYNOPSIS
+.Fd #include \*[Lt]magic.h\*[Gt]
+.Ft magic_t
+.Fn magic_open "int flags"
+.Ft void
+.Fn magic_close "magic_t cookie"
+.Ft const char *
+.Fn magic_error "magic_t cookie"
+.Ft const char *
+.Fn magic_file "magic_t cookie, const char *filename"
+.Ft const char *
+.Fn magic_buffer "magic_t cookie, const void *buffer, size_t length"
+.Ft void
+.Fn magic_setflags "magic_t cookie, int flags"
+.Ft int
+.Fn magic_check "magic_t cookie, const char *filename"
+.Ft int
+.Fn magic_compile "magic_t cookie, const char *filename"
+.Ft int
+.Fn magic_load "magic_t cookie, const char *filename"
+.Sh DESCRIPTION
+These functions
+operate on the magic database file
+which is described
+in
+.Xr magic __FSECTION__ .
+.Pp
+The function
+.Fn magic_open
+creates a magic cookie pointer and returns it. It returns NULL if
+there was an error allocating the magic cookie. The 
+.Ar flags
+argument specifies how the other magic functions should behave:
+.Bl -tag -width MAGIC_COMPRESS
+.It Dv MAGIC_NONE
+No special handling.
+.It Dv MAGIC_DEBUG
+Print debugging messages to stderr.
+.It Dv MAGIC_SYMLINK
+If the file queried is a symlink, follow it.
+.It Dv MAGIC_COMPRESS
+If the file is compressed, unpack it and look at the contents.
+.It Dv MAGIC_DEVICES
+If the file is a block or character special device, then open the device
+and try to look in its contents.
+.It Dv MAGIC_MIME
+Return a mime string, instead of a textual description.
+.It Dv MAGIC_CONTINUE
+Return all matches, not just the first.
+.It Dv MAGIC_CHECK
+Check the magic database for consistency and print warnings to stderr.
+.El
+.Pp
+The
+.Fn magic_close
+function closes the
+.Xr magic __FSECTION__
+database and deallocates any resources used.
+.Pp
+The
+.Fn magic_error
+function returns a textual explanation of the last error, or NULL if there was
+no error.
+.Pp
+The
+.Fn magic_file
+function returns a textual description of the contents of the
+.Ar filename
+argument, or NULL if an error occurred.
+.Pp
+The
+.Fn magic_buffer
+function returns a textual description of the contents of the
+.Ar buffer
+argument with
+.Ar length
+bytes size.
+.Pp
+The
+.Fn magic_setflags
+function, sets the 
+.Ar flags
+described above.
+.Pp
+The
+.Fn magic_check
+function can be used to check the validity of entries in the colon
+separated database files passed in as
+.Ar filename ,
+or NULL for the default database. It returns 0 on success and -1 on
+failure.
+.Pp
+The
+.Fn magic_compile
+function can be used to compile the the colon
+separated list of database files passed in as
+.Ar filename ,
+or NULL for the default database. It returns 0 on success and -1 on
+failure. The compiled files created are named from the
+.Xr basename 1
+of each file argument with ".mgc" appended to it.
+.Pp
+The
+.Fn magic_load
+function must be used to load the the colon
+separated list of database files passed in as
+.Ar filename ,
+or NULL for the default database
+before any magic queries can performed.
+.Sh RETURN VALUES
+The function
+.Fn magic_open
+returns a magic cookie on success and NULL on failure setting errno to
+an appropriate value.
+The
+.Fn magic_load ,
+.Fn magic_compile ,
+and
+.Fn magic_check
+functions return 0 on success and -1 on failure.
+The
+.Fn magic_file ,
+and
+.Fn magic_buffer 
+functions return a string on success and NULL on failure. The
+.Fn magic_error
+function returns a textual description of the errors of the above
+functions, or NULL if there was no error.
+.Sh FILES
+.Bl -tag -width __MAGIC__.mime.mgc -compact
+.It Pa __MAGIC__.mime
+The non-compiled magic mime database.
+.It Pa __MAGIC__.mime.mgc
+The compiled magic mime database.
+.It Pa __MAGIC__
+The non-compiled magic database.
+.It Pa __MAGIC__.mgc
+The compiled magic database.
+.El
+.Sh SEE ALSO
+.Xr file __CSECTION__ ,
+.Xr magic __FSECTION__