Shell Programming and Scripting

cat file1
col1|col2|col3
a|1|A
b|2|B

cat file2
col1|col2|col3
c|3|C

cat file3
col1|col2|col3
d|4|D
e|5|E

col1|col2
a|1
3|C
D|4

awk -F"|" '{ print $1,$2 }' file1 '{print $2,$3}' file2 '{print $3,$1}' file3

awk 'pattern {action}' input-file ...

awk -F"|" '{ print $1,$2 }' file1

'{print $2,$3}' file2 '{print $3,$1}' file3

awk '
  BEGIN {
    FS=OFS="|"
    print "col1|col2"
  }

  FNR==n+1 {
    print $p1, $p2
  }
' n=1 p1=1 p2=2 file1 p1=2 p2=3 file2 p1=3 p2=2 file3

col1|col2
a|1
3|C
D|4

Code:

awk -v answer42='col1|col2' '
  BEGIN {
    FS=OFS="|"
    print answer42
  }

  FNR==universe+1 {
    print $mouse1, $mouse2
  }
' FS=\| OFS=\| universe=1 mouse1=1 mouse2=2 file1 mouse1=2 mouse2=3 file2 mouse1=3 mouse2=2 file3

col1|col2
a|1
3|C
D|4

awk -F"|" '
function print_val(var){
  num=split(var, array,",");
  for(i=1;i<=num;i++){
    printf("%s%s",$array[i],i==num?RS:"|")
}
}
BEGIN{
  print "col1|col2"
}
FNR==1{
  ++file;
  next
}
file==1{
  print_val("1,2");
  nextfile
}
file==2{
  print_val("2,3");
  nextfile
}
file==3{
  print_val("3,2");
  nextfile
}
'   Input_file1  Input_file2  Input_file3

col1|col2
a|1
3|C
D|4