chkformreadfileFreeForm ND includes readfile, a simple interactive binary file
reader. The program has one required command line argument, the name
of the file to be read. You do not have to write format descriptions
to use readfile.
The readfile command has the following form:
readfile binary_data_fileWhen the program starts, it shows the available options, shown in
table 9.3. At the readfile prompt, type
these option codes to view binary encoded values. (Pressing return
repeats the last option.)
readfile program options
c | char -- 1 byte character |
s | short -- 2 byte signed integer |
l | long -- 4 byte signed integer |
f | float -- 4 byte single-precision floating point |
d | double -- 8 byte double-precision floating point |
uc | uchar -- 1 byte unsigned integer |
us | ushort -- 2 byte unsigned integer |
ul | ulong -- 4 byte unsigned integer |
b | Toggle between "big-endian" and your machine's native byte order |
p | Set new file position |
P | Show present file position and length |
h | Display this help screen |
q | Quit |
The options let you interactively read your way through the specified binary file. The first position in the file is 0. You must type the character(s) indicating variable type (e.g., us for unsigned short) to view each value, so you need to know the data types of variables in the file and the order in which they occur. If successive variables are of the same type, you can press Return to view each value after the first of that type.
You can toggle the byte-order switch on and off by typing b. The
byte-order option is used to read a binary data file that requires
byte swapping. This is the case when you need cross-platform access to
a file that is not byte-swapped, for example, if you are on a Unix
machine reading data from a CD-ROM formatted for a PC. When the switch
is on, type s or l to swap short or long integers
respectively, or type f or d to swap floats or doubles.
The readfile program does not byte swap the file itself (the
file is unchanged) but byte swaps the data values internally for
display purposes only.
To go to another position in the file, type p. You are prompted
to enter the new file position in bytes. If, for example, each value
in the file is 4 bytes long and you type 16, you will be positioned at
the first byte of the fifth value. If you split fields (by not
repositioning at the beginning of a field), the results will probably
be garbage. Type P to find out your current position in the file
and total file length in bytes. Type q to exit from
readfile.
You can also use an input command file rather than entering commands
directly. In that case, the readfile command has the following
form:
readfile binary_data_file < input_command_file