Transform delimited fields to lines with name and value

File a is containing field names:

timestamp,name,ip

File b contains values:

2021-12-17 16:01:19.970,app1,10.0.0.0
2021-12-17 16:01:19.260,app1,10.0.0.1

When I use awk as follows:

awk 'BEGIN{FS=",";OFS="\n"} {if(NR%3==0){print "----"};$1=$1;print;}' b

I get:

----
2021-12-17 16:01:19.970
app1
10.0.0.0
----
2021-12-17 16:01:19.260
app1
10.0.0.1

Any way to merge key:value in each line?
The output I want is:

----
timestamp:2021-12-17 16:01:19.970
app:app1
ip:10.0.0.0
----
timestamp:2021-12-17 16:01:19.260
app:app1
ip:10.0.0.1

>Solution :

With your shown samples, please try following awk program.

awk '
BEGIN{ FS="," }
FNR==NR{
  for(i=1;i<=NF;i++){
    heading[i]=$i
  }
  next
}
{
  print "----"
  for(i=1;i<=NF;i++){
    print heading[i]":"$i
  }
}
' filea fileb

Explanation: Adding detailed explanation for above.

awk '                     ##Starting awk program from here.
BEGIN{ FS="," }           ##Stating BEGIN section of this program and set FS to , here.
FNR==NR{                  ##Checking condition which will be TRUE when filea is being read.
  for(i=1;i<=NF;i++){     ##Traversing through all fields here.
    heading[i]=$i         ##Setting heading array index as i and value as current field.
  }
  next                    ##next will skip all further statements from here.
}
{
  print "----"            ##printing ---- here.
  for(i=1;i<=NF;i++){     ##Traversing through all fields here.
    print heading[i]":"$i ##Printing heading with index i and colon and value of current field.
  }
}
' filea fileb             ##Mentioning Input_file names here.