Question

How can i append the next line to a previous line in a file, delimited by pipe symbol?

Expectd Input — content of input.txt

ABC    
BCD    
DEF    
EFG    
FGH    

Expectd Output — content of output.txt

|ABC|BCD|    
|BCD|DEF|    
|DEF|EFG|    
|EFG|FGH|    
|FGH||

Answer 1

paste - - < input-txt

is a good start, but it does not add your desired delimiters. For that, try:

 paste - - < input-txt | awk '{$1=$1; print OFS $0 OFS}' OFS=\|

(Or any of many other ways to insert the | symbol between the fields! This version emits |FGH| instead of |FGH|| on the final line.)

Or:

 sed 1d input-txt | paste -d \| input - | sed 's/^\|$/|/g'