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Full Discussion: ConCATenating binaries but excluding last bytes from each file
Top Forums UNIX for Dummies Questions & Answers ConCATenating binaries but excluding last bytes from each file Post 302877743 by Don Cragun on Tuesday 3rd of December 2013 08:43:01 AM
Old 12-03-2013
This isn't highly efficient (since it will copy the redundant bytes to the output file multiple time, doesn't try to align block sizes to disk block boundaries, uses small input block sizes if you have a large file that starts at a small [but non-zero] offset), but it seems to do what you want. You can make it considerably more complex to verify that the ranges of bytes specified by the input files don't leave any holes in the output file and to avoid copying duplicated data more than once. The checks for names that contain a "-" but are not just a string of digits followed by a "-" followed by a string of digits could be simplified with ksh and bash specific constructs. But the constructs used here should be portable to any shell that handles basic POSIX shell parameter expansion requirements correctly.

This is too simplistic to work if you want to process a file with a starting offset that is close to your process' maximum available address space. (In other words it probably won't work for terabyte sized files where the starting offset in one or more of your input files is relatively large.) But, it should give you a starting point for a more advanced script:
Code:
#!/bin/ksh
IAm=${0##*/}
of="final.$$"
> $of   # create zero-length temporary output file
maxe=0
for i in *-*
do      printf "Looking at \"%s\"\n" "$i"
        b=${i%%-*}
        e=${i##*-}
        if [ -z "$b" ] || [ -z "$e" ] || [ "$i" != "$b-$e" ] ||
                [ "$b" != "${b#*[!0-9]}" ] || [ "$e" != "${e#*[!0-9]}" ]
        then    continue
        fi
        if [ $e -gt $maxe ]
        then    maxe=$e
        fi
        if [ $b -gt 0 ]
        then    seek="ibs=102400 obs=$b seek=1"
        else    seek='bs=10240'
        fi
        echo starting dd if=$i of=$of $seek conv=notrunc
        dd if=$i of=$of $seek conv=notrunc
done
if [ $maxe -gt 0 ]
then    printf "Creating 0-%d\n" $maxe
        mv $of 0-$maxe
        exit
fi
rm $of
printf "%s: No input files found; no output file created.\n" "$IAm" >&2
exit 1

I use the Korn shell, but this script will work with any POSIX conforming shell without changing anything other than the first line in the script to specify your shell.
This User Gave Thanks to Don Cragun For This Post:
fpmurphy
 

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LEARN ABOUT V7

dd

DD(1)							      General Commands Manual							     DD(1)

NAME

       dd - convert and copy a file

SYNOPSIS

       dd [option=value] ...

DESCRIPTION

       Dd  copies  the specified input file to the specified output with possible conversions.	The standard input and output are used by default.
       The input and output block size may be specified to take advantage of raw physical I/O.

       option	      values
       if=	      input file name; standard input is default
       of=	      output file name; standard output is default
       ibs=n	      input block size n bytes (default 512)
       obs=n	      output block size (default 512)
       bs=n	      set both input and output block size, superseding ibs and obs; also, if no conversion is specified, it is particularly effi-
		      cient since no copy need be done
       cbs=n	      conversion buffer size
       skip=n	      skip n input records before starting copy
       files=n	      copy n files from (tape) input
       seek=n	      seek n records from beginning of output file before copying
       count=n	      copy only n input records
       conv=ascii     convert EBCDIC to ASCII
	    ebcdic    convert ASCII to EBCDIC
	    ibm       slightly different map of ASCII to EBCDIC
	    lcase     map alphabetics to lower case
	    ucase     map alphabetics to upper case
	    swab      swap every pair of bytes
	    noerror   do not stop processing on an error
	    sync      pad every input record to ibs
	    ... , ... several comma-separated conversions

       Where  sizes  are  specified,  a number of bytes is expected.  A number may end with k, b or w to specify multiplication by 1024, 512, or 2
       respectively; a pair of numbers may be separated by x to indicate a product.

       Cbs is used only if ascii or ebcdic conversion is specified.  In the former case cbs characters are placed into the conversion buffer, con-
       verted to ASCII, and trailing blanks trimmed and new-line added before sending the line to the output.  In the latter case ASCII characters
       are read into the conversion buffer, converted to EBCDIC, and blanks added to make up an output record of size cbs.

       After completion, dd reports the number of whole and partial input and output blocks.

       For example, to read an EBCDIC tape blocked ten 80-byte EBCDIC card images per record into the ASCII file x:

	      dd if=/dev/rmt0 of=x ibs=800 cbs=80 conv=ascii,lcase

       Note the use of raw magtape.  Dd is especially suited to I/O on the raw physical devices because it allows reading and writing in arbitrary
       record sizes.

       To skip over a file before copying from magnetic tape do (dd of=/dev/null; dd of=x) </dev/rmt0

SEE ALSO

       cp(1), tr(1)

DIAGNOSTICS

       f+p records in(out): numbers of full and partial records read(written)

BUGS

       The  ASCII/EBCDIC  conversion  tables  are  taken  from the 256 character standard in the CACM Nov, 1968.  The `ibm' conversion, while less
       blessed as a standard, corresponds better to certain IBM print train conventions.  There is no universal solution.

       Newlines are inserted only on conversion to ASCII; padding is done only on conversion to EBCDIC.  These should be separate options.

																	     DD(1)
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