-.\" $Id: file.man,v 1.60 2007/01/08 17:08:48 christos Exp $
+.\" $Id: file.man,v 1.61 2007/01/10 18:59:03 christos Exp $
.Dd January 8, 2007
.Dt FILE __CSECTION__
.Os
characters and is probably safe to read on an
.Dv ASCII
terminal),
-.Dv executable
+.Em executable
(the file contains the result of compiling a program
in a form understandable to some
.Dv UNIX
kernel or another),
or
-.Dv data
+.Em data
meaning anything else (data is usually
.Sq binary
or non-printable).
that are known to contain binary data.
When modifying the file
.Pa __MAGIC__
-or the program itself,
+or the program itself, make sure to
.Em "preserve these keywords" .
People depend on knowing that all the readable files in a directory
have the word
The canonical example of this is a binary executable (compiled program)
.Dv a.out
file, whose format is defined in
+.In elf.h ,
.In a.out.h
and possibly
.In 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 \s-1UNIX\s0 operating system
+These files have a
+.Sq "magic number"
+stored in a particular place
+near the beginning of the file that tells the
+.Dv UNIX operating system
that the file is a binary executable, and which of several types thereof.
-The concept of `magic number' has been applied by extension to data files.
+The concept of a
+.Sq "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
.In names.h
that can appear anywhere in the first few blocks of a file.
For example, the keyword
-.Dv .br
+.Em .br
indicates that the file is most likely a
.Xr troff 1
input file, just as the keyword
-.Dv struct
+.Em struct
indicates a C program.
These tests are less reliable than the previous
two groups, so they are performed last.
Do not prepend filenames to output lines (brief mode).
.It Fl c Fl \-checking\-printout
Cause a checking printout of the parsed form of the magic file.
-This is usually used in conjunction with
-.It Fl m
-to debug a new magic file before installing it.
+This is usually used in conjunction with the
+.Fl m
+flag to debug a new magic file before installing it.
.It Fl C Fl \-compile
-Write a magic.mgc output file that contains a pre-parsed version of
-file.
+Write a
+.Pa magic.mgc
+output file that contains a pre-parsed version of the magic file.
.It Fl f Fl \-files\-from Ar namefile
Read the names of the files to be examined from
.Ar namefile
.Ar namefile
or at least one filename argument must be present;
to test the standard input, use
-.Dq \-
+.Sq \-
as a filename argument.
.It Fl F Fl \-separator Ar separator
Use the specified string as the separator between the filename and the
file result returned. Defaults to
-.Dq \: .
+.Sq \&: .
.It Fl h Fl \-no\-dereference
option causes symlinks not to be followed
(on systems that support symbolic links). This is the default if the
.It Fl z Fl \-uncompress
Try to look inside compressed files.
.It Fl 0 Fl \-print0
-Output a null character (
-.Sq \0 )
+Output a null character
+.Sq \e0
after the end of the filename. Nice to
.Xr cut 1
the output. This does not affect the separator which is still printed.
.It Fl \-help
-.El
Print a help message and exit.
+.El
.Sh FILES
.Bl -tag -width __MAGIC__.mime.mgc -compact
.It Pa __MAGIC__.mgc
options.
.Sh SEE ALSO
.Xr magic __FSECTION__ ,
-.Xr strings 1u ,
+.Xr strings 1 ,
.Xr od 1 ,
.Xr hexdump 1
.Sh STANDARDS CONFORMANCE
is that this version treats any white space
as a delimiter, so that spaces in pattern strings must be escaped.
For example,
-.br
+.Bd -literal -offset indent
>10 string language impress\ (imPRESS data)
-.br
+.Ed
+.Pp
in an existing magic file would have to be changed to
-.br
+.Bd -literal -offset indent
>10 string language\e impress (imPRESS data)
-.br
+.Ed
+.Pp
In addition, in this version, if a pattern string contains a backslash,
it must be escaped.
For example
-.br
+.Bd -literal -offset indent
0 string \ebegindata Andrew Toolkit document
-.br
+.Ed
+.Pp
in an existing magic file would have to be changed to
-.br
+.Bd -literal -offset indent
0 string \e\ebegindata Andrew Toolkit document
-.br
+.Ed
.Pp
SunOS releases 3.2 and later from Sun Microsystems include a
.Nm
.Sq &
operator, used as,
for example,
-.br
+.Bd -literal -offset indent
>16 long&0x7fffffff >0 not stripped
+.Ed
.Sh MAGIC DIRECTORY
The magic file entries have been collected from various sources,
mainly USENET, and contributed by various authors.
(rename it to
.Pa __MAGIC__.orig ).
.Sh EXAMPLES
-.nf
+.Bd -literal -offset indent
$ 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
$ file -i file.c file /dev/{wd0a,hda}
file.c: text/x-c
file: application/x-executable, dynamically linked (uses shared libs),
-not stripped
+ not stripped
/dev/hda: application/x-not-regular-file
/dev/wd0a: application/x-not-regular-file
-.fi
+.Ed
.Sh HISTORY
There has been a
.Nm
There must be a better way to automate the construction of the Magic
file from all the glop in Magdir.
What is it?
-Better yet, the magic file should be compiled into binary (say,
-.Xr ndbm 3
-or, better yet, fixed-length
-.Dv ASCII
-strings for use in heterogenous network environments) for faster startup.
-Then the program would run as fast as the Version 7 program of the same name,
-with the flexibility of the System V version.
+.\" Compilation support has been done
+.\" Better yet, the magic file should be compiled into binary (say,
+.\" .Xr ndbm 3
+.\" or, better yet, fixed-length
+.\" .Dv ASCII
+.\" strings for use in heterogenous network environments) for faster startup.
+.\" Then the program would run as fast as the Version 7 program of the same
+.\" name, with the flexibility of the System V version.
.Pp
.Nm
uses several algorithms that favor speed over accuracy,
.Pp
The support for text files (primarily for programming languages)
is simplistic, inefficient and requires recompilation to update.
-.Pp
-There should be an
-.Dv else
-clause to follow a series of continuation lines.
-.Pp
-The magic file and keywords should have regular expression support.
+.\" Else support has been done
+.\" There should be an
+.\" .Dv else
+.\" clause to follow a series of continuation lines.
+.\" .Pp
+.\" Regular expression support has been done
+.\" The magic file and keywords should have regular expression support.
Their use of
.Dv ASCII TAB
as a field delimiter is ugly and makes
.Sq *
for the offset value.
.Pp
-Another optimization would be to sort
-the magic file so that we can just run down all the
-tests for the first byte, first word, first long, etc, once we
-have fetched it.
+.\" Sorting has been done.
+.\" Another optimization would be to sort
+.\" the magic file so that we can just run down all the
+.\" tests for the first byte, first word, first long, etc, once we
+.\" have fetched it.
Complain about conflicts in the magic file entries.
Make a rule that the magic entries sort based on file offset rather
than position within the magic file?
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