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Fix the First Line of a File

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Notes

I have a text file, but the first line might need modification. What to do?

Reach for perl of course!

This requires a variation of the generic patch_file process described here.

The examples.sh script demonstrates the principle. The example is actually taking a file in Intel Hex format and pre-pending an Extended Linear Address record if one is not already present.

Example

$ ./examples.sh
Installing example.hex from template..

Original example.hex (head only)..
:10000000008000208D030000CD030000CF0300001E
:1000100000000000000000000000000000000000E0
:10002000000000000000000000000000D1030000FC
:100030000000000000000000D3030000D503000012
:10004000D7030000D7030000D7030000D703000048
:10005000D703000000000000D7030000D703000012
:10006000D7030000D7030000D7030000D703000028
:10007000D7030000D7030000D7030000D703000018
:10008000D7030000D7030000D7030000D703000008
:10009000D7030000D7030000D7030000D7030000F8

Step 1: Patching the first line (with file backup)

Cummulative diffs..
1d0
< :020000040000FA

Step 2: Try patching again - should not duplicate (without backup)

Cummulative diffs..
1d0
< :020000040000FA

Resulting example.hex (head only)..
:020000040000FA
:10000000008000208D030000CD030000CF0300001E
:1000100000000000000000000000000000000000E0
:10002000000000000000000000000000D1030000FC
:100030000000000000000000D3030000D503000012
:10004000D7030000D7030000D7030000D703000048
:10005000D703000000000000D7030000D703000012
:10006000D7030000D7030000D7030000D703000028
:10007000D7030000D7030000D7030000D703000018
:10008000D7030000D7030000D7030000D703000008

Credits and References

About LCK#11 perl
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This page is a web-friendly rendering of my project notes shared in the LittleCodingKata GitHub repository.

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