11 Scripts and plain-text files

Question 1

Magic bytes for scripts intended for processing by interpreter named in rest of line

Answer 1

!/bin/bash

Question 2

Magic bytes for Executable and Linkable format

Answer 2

0x7f (backspace)

‘E’ ‘L’ ‘F’

Question 3

Writing a script

Answer 3

Start with magic bytes + name of interpreter

chmod +x file

./file

OR
bash file

Question 4

Plain text file problems

Answer 4

1. Line feeds/tabs
2. MS - two control character sequence for end of line = carriage return + line feed
3. Conversions via dos2unix/iconv
4. Flowed plain text format – do we store LF within paragraph, and line wrapping of paragraph happens only when the file is being displayed – LF used to terminate paragraphs

Question 5

Byte order mark

Answer 5

Windows notepad
BOM U+FEFF
invisible character if FEFF
invalid if FFEF
check to derive endianness of a 16 bit file
subsequently used as a marker for UTF8 formats
interferes with magic bytes for Unix shell scripts #!