How to understand pipeline built with Grep and Sed

Question

Example

I'm trying to understand below line of shell code.

   grep "^1  " file0 | grep -v MODEL | sed 's/./&E/86' | sed 's/./&  /8' | sed 's/./&  /20' > file1

Question

Could someone explain what this pipeline does?

Answer 1

# Add "E" after the 86th character
sed 's/./&E/86'

# Add "  " after the 8th character
sed 's/./&  /8'

# Add "  " after the 20th character
sed 's/./&  /20'

Answer 2

除了在sed之前使用多个grep管道之外，您还可以将它们全部组合成一个sed表达式

sed '/^1  /{/MODEL/b;s/./&E/86;s/./&  /8;s/./&  /20}' file0 > file1