UNIX for Beginners Questions & Answers

:/data/files/jlj > cat sample.dat
a~b~c~d~12~r
a~b~c~d~12~r
a~b~c~d~12~r
a~b~c~d~12~r
:/data/files/jlj > awk -F"~" 'NF < 12 { $12 = FS; print }' OFS="~" sample.dat
a~b~c~d~12~r
a~b~c~d~12~r
a~b~c~d~12~r
a~b~c~d~12~r
:/data/files/jlj > awk -F~ 'NF < 12 { $12 = FS; print }' OFS=~ sample.dat
a/b/c/d/12/r
a/b/c/d/12/r
a/b/c/d/12/r
a/b/c/d/12/r

awk -F"~" '{          ##Making field separator as ~ here for each line of Input_file.
i=NF;                 ##creating a variable named i whose value is equal to value of NF, NF is out of box variable which defines number of fields in a line of Input_file.
while(i<14){          ##Initiating while loop here which will run from i value from 0 to 13 here.
  val=val?val "~":"~";##creating a variable named val whose value will be having its value to ~ on very first occurrence and will concatenate itself each time with its previous value. Where ? means if condition is TRUE then execute statement followed by it or condition is FALSE then execute statement after :
  i++                 ##incrementing the value of variable named i here.
};
print $0 val;         ##printing current line and value of variable val.
val=""                ##nullifying value of val here.
}' Input_file         ##Mentioning Input_file here.

/data/files/jlj > uname -a
SunOS ux562z3 5.10 Generic_150400-17 sun4u sparc SUNW,SPARC-Enterprise

/data/files/jlj > nawk -F"~" 'NF < 12 { $12 = FS; print }' O
a~b~c~d~12~r~~~~~~~
a~b~c~d~12~r~~~~~~~
a~b~c~d~12~r~~~~~~~
a~b~c~d~12~r~~~~~~~