NetBSD/dist/file/doc/libmagic.3

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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 5 .
.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 5
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 /usr/share/misc/magic.mime.mgc -compact
.It Pa /usr/share/misc/magic.mime
The non-compiled magic mime database.
.It Pa /usr/share/misc/magic.mime.mgc
The compiled magic mime database.
.It Pa /usr/share/misc/magic
The non-compiled magic database.
.It Pa /usr/share/misc/magic.mgc
The compiled magic database.
.El
.Sh SEE ALSO
.Xr file 1 ,
.Xr magic 5 
.Sh AUTHORS
M<EFBFBD>ns Rullg<6C>rd Initial libmagic implementation,
and configuration.
Christos Zoulas API cleanup, error code and allocation handling.