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Top Forums Shell Programming and Scripting how to get data from hex file using SED or AWK based on pattern sign Post 302564018 by alister on Wednesday 12th of October 2011 03:16:37 PM
Old 10-12-2011
Since we don't know exactly what platform you're running on, my proposal endeavours to restrict itself to ubiquitous POSIX functionality. Also, it makes the same assumptions you've made. Specifically:

Quote:
Originally Posted by sameucho
I simplified the task supposing there will not be another occurence of such combination of 'sign' bytes before the desired values which are to be collected.
I did not test the following code, but I did my best to mind the details. If it doesn't work, please post any error messages, how the behavior deviates from what's expected, and which operating system(s) this needs to run on. Also, if the following code is insufficient, it would help to have a sample of the binary data to test against (upload it somewhere and link us). I'm feeling a bit lazy today and I'm not interested in creating my own mock data Smilie (although I suppose I could reverse the hexdump with AWK if I were feeling industrious).


Code:
od -An -td1 binfile | tr -s ' \t' '\n\n' | awk '
    NR==1 && length==0   { getline }
    $0==180              { i=1; getline; getline; getline }
    i==1 && $0==128      { ++i; getline }
    i==2 && $0==1        { ++i; getline }
    i==3 && $0==12       { ++i; getline }
    i==4 && $0==175      { ++i; getline }
    i==5 && $0==131      { ++i; getline; pr_bytes(); getline }
    i==6 && $0==132      { getline; pr_bytes(); printf("%s", s) }
    i!=4 && i!=5         { i=0; s="" }

    function pr_bytes() {
        j=$0
        while (j--) {
                getline
                s=s sprintf("%.2X%s", $0, (j ? OFS : ORS))
        }
    }
'


Since AWK is not required to support hexadecimal constants or numeric strings, od dumps byte values in base 10. tr is used to replace all spaces and tabs with newlines. AWK then reads one line at a time, with each line either containing one byte value in decimal or nothing at all.

The AWK script:
* Discard a leading blank line if present (a by-product of leading whitespace in od output).
* i keeps track of which state is sought.
* pr_bytes() reads the value of the current byte and reads that many subsequent bytes. The bytes are stored in s as a space-delimited string terminated by a newline.
* If at any point a byte value does not match what's expected, the line will fallthrough to the bottom, where i and s are reset.
* The output is two lines of text per record. Line 1 corresponds to what you've referred to as X, line 2 to Y. Each line is a space-delimited sequence of hexadecimal byte values.

Regards,
Alister

Last edited by alister; 10-12-2011 at 04:45 PM.. Reason: Added missing getline and corrected conditional
 

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GETDELIM(3)						   BSD Library Functions Manual 					       GETDELIM(3)

NAME
getdelim, getline -- read a delimited record from a stream LIBRARY
Standard C Library (libc, -lc) SYNOPSIS
#include <stdio.h> ssize_t getdelim(char ** restrict lineptr, size_t * restrict n, int delimiter, FILE * restrict stream); ssize_t getline(char ** restrict lineptr, size_t * restrict n, FILE * restrict stream); DESCRIPTION
The getdelim() function reads from the stream until it encounters a character matching delimiter, storing the input in *lineptr. The buffer is NUL-terminated and includes the delimiter. The delimiter character must be representable as an unsigned char. If *n is non-zero, then *lineptr must be pre-allocated to at least *n bytes. The buffer should be allocated dynamically; it must be possible to free(3) *lineptr. getdelim() ensures that *lineptr is large enough to hold the input, updating *n to reflect the new size. The getline() function is equivalent to getdelim() with delimiter set to the newline character. RETURN VALUES
The getdelim() and getline() functions return the number of characters read, including the delimiter. If no characters were read and the stream is at end-of-file, the functions return -1. If an error occurs, the functions return -1 and the global variable errno is set to indi- cate the error. The functions do not distinguish between end-of-file and error, and callers must use feof(3) and ferror(3) to determine which occurred. EXAMPLES
The following code fragment reads lines from a file and writes them to standard output. char *line = NULL; size_t linesize = 0; ssize_t linelen; while ((linelen = getline(&line, &linesize, fp)) != -1) fwrite(line, linelen, 1, stdout); if (ferror(fp)) perror("getline"); ERRORS
[EINVAL] lineptr or n is a NULL pointer. [EOVERFLOW] More than SSIZE_MAX characters were read without encountering the delimiter. The getdelim() and getline() functions may also fail and set errno for any of the errors specified in the routines fflush(3), malloc(3), read(2), stat(2), or realloc(3). SEE ALSO
ferror(3), fgets(3), fopen(3) STANDARDS
The getdelim() and getline() functions conform to IEEE Std 1003.1-2008 (``POSIX.1''). BSD
June 30, 2010 BSD
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