guy@sun.uucp (Guy Harris) (09/03/85)
So here's a manual page for the format accepted by the "file" made by adding
the changes I posted to the S5R2 version.
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..
.TH MAGIC 4
.SH NAME
magic \- file command's magic number file
.SH DESCRIPTION
The
.IR file (1)
command identifies the type of a file using,
among other tests,
a test for whether the file begins with a certain
.IR "magic number" .
The file
.B /etc/magic
specifies what magic numbers are to be tested for,
what message to print if a particular magic number is found,
and additional information to extract from the file.
.PP
Each line of the file specifies a test to be performed.
A test compares the data starting at a particular offset
in the file with a 1-byte, 2-byte, or 4-byte numeric value or
a string. If the test succeeds, a message is printed.
The line consists of the following fields:
.IP offset \w'message'u+2n
A number specifying the offset, in bytes, into the file of the data
which is to be tested.
.IP type
The type of the data to be tested. The possible values are:
.RS
.IP byte \w'message'u+2n
A one-byte value.
.IP short
A two-byte value.
.IP long
A four-byte value.
.IP string
A string of bytes.
.RE
.IP
The types
.BR byte ,
.BR short ,
and
.B long
may optionally be followed by a mask specifier of the form
.BI & number\fR.
If a mask specifier is given, the value is AND'ed with the
.I number
before any comparisons are done. The
.I number
is specified in C form; e.g.
.B 13
is decimal,
.B 013
is octal, and
.B 0x13
is hexadecimal.
.IP test
The value to be compared with the value from the file. If the type is
numeric, this value
is specified in C form; if it is a string, it is specified as a C string
with the usual escapes permitted (e.g. \en for new-line).
.IP
Numeric values
may be preceded by a character indicating the operation to be performed.
It may be
.BR = ,
to specify that the value from the file must equal the specified value,
.BR < ,
to specify that the value from the file must be less than the specified
value,
.BR > ,
to specify that the value from the file must be greater than the specified
value,
or
.B x
to specify that any value will match. If the character
is omitted, it is assumed to be
.BR = .
.IP
For string values, the byte string from the
file must match the specified byte string; the byte string from the file
which is matched is the same length as the specified byte string.
.IP message
The message to be printed if the comparison succeeds. If the string
contains a
.IR printf (3S)
format specification, the value from the file (with any specified masking
performed) is printed using the message as the format string.
.PP
Some file formats contain additional information which is to be printed
along with the file type. A line which begins with the character
.B >
indicates additional tests and messages to be printed. If the test on the
line preceding the first line with a
.B >
succeeds, the tests specified in all the subsequent lines beginning with
.B >
are performed, and the messages printed if the tests succeed. The next
line which does not begin with a
.B >
terminates this.
.SH BUGS
There should be more than one level of subtests, with the level indicated by
the number of
.B >
at the beginning of the line.
.SH SEE ALSO
file(1) in the
\f2\s-1UNIX\s+1 System User Reference Manual\fR.
.\" %W% of %G%guy@sun.uucp (Guy Harris) (09/05/85)
> So here's a manual page for the format accepted by the "file" made by adding > the changes I posted to the S5R2 version. So here's a manual page made by ripping the d*mn header off so that the ^Gs in the header don't get stripped of by "inews". Rip the header material from the front of any other S5R2 man page and stick them on the front. Special thanks to the person who decided that sticking almost-identical boilerplace on the front of *every* man page was a "solution" to some problem; without their help, this would not have been necessary. *Very* bad engineering, guys; you might want to post what the reason was, so that somebody on the net can suggest a sane solution... .TH MAGIC 4 .SH NAME magic \- file command's magic number file .SH DESCRIPTION The .IR file (1) command identifies the type of a file using, among other tests, a test for whether the file begins with a certain .IR "magic number" . The file .B /etc/magic specifies what magic numbers are to be tested for, what message to print if a particular magic number is found, and additional information to extract from the file. .PP Each line of the file specifies a test to be performed. A test compares the data starting at a particular offset in the file with a 1-byte, 2-byte, or 4-byte numeric value or a string. If the test succeeds, a message is printed. The line consists of the following fields: .IP offset \w'message'u+2n A number specifying the offset, in bytes, into the file of the data which is to be tested. .IP type The type of the data to be tested. The possible values are: .RS .IP byte \w'message'u+2n A one-byte value. .IP short A two-byte value. .IP long A four-byte value. .IP string A string of bytes. .RE .IP The types .BR byte , .BR short , and .B long may optionally be followed by a mask specifier of the form .BI & number\fR. If a mask specifier is given, the value is AND'ed with the .I number before any comparisons are done. The .I number is specified in C form; e.g. .B 13 is decimal, .B 013 is octal, and .B 0x13 is hexadecimal. .IP test The value to be compared with the value from the file. If the type is numeric, this value is specified in C form; if it is a string, it is specified as a C string with the usual escapes permitted (e.g. \en for new-line). .IP Numeric values may be preceded by a character indicating the operation to be performed. It may be .BR = , to specify that the value from the file must equal the specified value, .BR < , to specify that the value from the file must be less than the specified value, .BR > , to specify that the value from the file must be greater than the specified value, or .B x to specify that any value will match. If the character is omitted, it is assumed to be .BR = . .IP For string values, the byte string from the file must match the specified byte string; the byte string from the file which is matched is the same length as the specified byte string. .IP message The message to be printed if the comparison succeeds. If the string contains a .IR printf (3S) format specification, the value from the file (with any specified masking performed) is printed using the message as the format string. .PP Some file formats contain additional information which is to be printed along with the file type. A line which begins with the character .B > indicates additional tests and messages to be printed. If the test on the line preceding the first line with a .B > succeeds, the tests specified in all the subsequent lines beginning with .B > are performed, and the messages printed if the tests succeed. The next line which does not begin with a .B > terminates this. .SH BUGS There should be more than one level of subtests, with the level indicated by the number of .B > at the beginning of the line. .SH SEE ALSO file(1) in the \f2\s-1UNIX\s+1 System User Reference Manual\fR. .\" %W% of %G%