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Full Discussion: Get file's first x bytes
Top Forums Shell Programming and Scripting Get file's first x bytes Post 302805765 by spacebar on Friday 10th of May 2013 10:15:43 PM
Old 05-10-2013
Here are some examples of using 'dd' to accomplish what you are asking:
Code:
# dd outputs 1st 5 bytes of file to screen with diagnostic info
dd if=input_file bs=1 count=5
# dd outputs 1st 5 bytes of file to screen with diagnostic info going to file
dd if=input_file bs=1 count=5 2>test.txt
# dd outputs 1st 5 bytes of file to file with diagnostic info going to file
dd if=input_file bs=1 count=5 of=output_file 2>test.txt

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LIPO(1) 						      General Commands Manual							   LIPO(1)

NAME
lipo - create or operate on fat files SYNOPSIS
lipo [-info] [-detailed_info] [-arch arch_type input_file] ... [ input_file] ... [-create] [-thin arch_type] [-replace arch_type file- name] ... [-remove arch_type] ... [-extract arch_type] ... [-extract_family arch_type] ... [-output output_file] [-segalign arch_type value] ... DESCRIPTION
The lipo command creates or operates on ``fat'' (multi-architecture) files. It only ever produces one output file, and never alters the input file. The operations that lipo performs are: listing the architecture types in a fat file; creating a single fat file from one or more input files; thinning out a single fat file to one specified architecture type; and extracting, replacing, and/or removing architec- tures types from the input file to create a single new fat output file. Only one option can be specified, with the exception of -arch, -output, and -segalign, which are used in combination with other options. The input_file argument is required, and only the -create option allows more than one input_file to be specified. The -output flag must be used, except with the -info and -detailed_info flags. The arch_type arguments may be any of the supported architecture names listed in the man page arch(3)exceptforVAXandMips. OPTIONS
-info Briefly list the architecture types in the input fat file (just the names of each architecture). -detailed_info Display a detailed list of the architecture types in the input fat file (all the the information in the fat header, for each archi- tecture in the file). -arch arch_type input_file Tells lipo that input_file contains the specified architecture type. The -arch arch_type specification is unnecessary if input_file is an object file, a fat file, or some other file whose architecture(s) lipo can figure out. -output output_file Specifies its argument to be the output file. -create Take the input files (or file) and create one fat output file from them. -thin arch_type Take one input file and create a thin output file with the specified arch_type. -replace arch_type file_name Take one fat input file; in the output file, replace the arch_type contents of the input file with the contents of the specified file_name. -remove arch_type Take one fat input file and remove the arch_type from that fat file, placing the result in the output file. -extract arch_type Take one fat input file and copy the arch_type from that fat file into a fat output file containing only that architecture. -extract_family arch_type Take one fat input file and copy all of the arch_types for the family that arch_type is in from that fat file into an output file containing only those architectures. The file will be thin if only one architecture is found or fat otherwise. -segalign arch_type value Set the segment alignment of the specified arch_type when creating a fat file containing that architecture. value is a hexadecimal number that must be an integral power of 2. This is only needed when lipo can't figure out the alignment of an input file (cur- rently not an object file), or when it guesses at the alignment too conservatively. The default for files unknown to lipo is 0 (2^0, or an alignment of one byte), and the default alignment for archives is 4 (2^2, or 4-byte alignment). SEE ALSO
arch(3) Apple Computer, Inc. October 23, 1997 LIPO(1)
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