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Top Forums Shell Programming and Scripting Update file record inside read loop Post 302742631 by Corona688 on Tuesday 11th of December 2012 11:03:09 AM
Old 12-11-2012
Not really, no. There is no seamless 'insert' operation for a file. To add extra data to the middle of a file, you must rewrite all the data that comes after it. That is why inserting data is so complicated, you never really do so.

The usual solutions for doing it all in one step, ed or sed -i, still use a temp file in many implementations.

So, since your records aren't fixed-width, the answer is no. If they were fixed-width, you could change any record without changing the length of the line, making it more possible, but fixed-width records are a difficult thing to handle in shell!

Last edited by Corona688; 12-11-2012 at 12:09 PM..
 

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srec_stewie(5)							File Formats Manual						    srec_stewie(5)

NAME
srec_stewie - Stewie's binary file format DESCRIPTION
If you have a URL for documentation of this format, please let me know. Any resemblance to the Motorola S-Record is superficial, and extends only to the data records. The header records and termination records are completely different. None of the other Motorola S-Records record type are available. The Records All records start with an ASCII capital S character, value 0x53, followed by a type specifier byte. All records consist of binary bytes. The Header Record Each file starts with a fixed four byte header record. +-----+------+------+------+ |0x53 | 0x30 | 0x30 | 0x33 | +-----+------+------+------+ The Data Records Each data record consists of 5 fields. These are the type field, length field, address field, data field, and the checksum. The lines always start with a capital S character. +-----+------+---------------+---------+------+----------+ |0x53 | Type | Record Length | Address | Data | Checksum | +-----+------+---------------+---------+------+----------+ Type The type field is a one byte field that specifies whether the record has a two-byte address field (0x31), a three-byte address field (0x32) or a four-byte address field (0x33). The address is big-endian. Record Length The record length field is a one byte field that specifies the number of bytes in the record following this byte. Address This is a 2-, 3- or 4-byte address that specifies where the data in the record is to be loaded into memory. Data The data field contains the executable code, memory-loadable data or descriptive information to be transferred. Checksum The checksum is a one byte field that represents the least significant byte of the one's complement of the sum of the values repre- sented by the bytes making up the record's length, address, and data fields. The Termination Record Each file ends with a fixed two byte termination record. +-----+------+ |0x53 | 0x38 | +-----+------+ Size Multiplier In general, binary data will expand in sized by approximately 1.2 times when represented with this format. EXAMPLE
Here is an hex-dump example file. It contains the data "Hello, World[rq] to be loaded at address 0. 0000: 53 30 30 33 53 31 10 00 00 48 65 6C 6C 6F 2C 20 S003S1...Hello, 0010: 57 6F 72 6C 64 0A 9D 53 38 World..S8 COPYRIGHT
srec_cat version 1.58 Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Peter Miller The srec_cat program comes with ABSOLUTELY NO WARRANTY; for details use the 'srec_cat -VERSion License' command. This is free software and you are welcome to redistribute it under certain conditions; for details use the 'srec_cat -VERSion License' command. AUTHOR
Peter Miller E-Mail: pmiller@opensource.org.au //* WWW: http://miller.emu.id.au/pmiller/ Reference Manual SRecord srec_stewie(5)
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