Shell Programming and Scripting

hi

i have a file like

Code:

1,"A","B"
2,"C","D"
1,"E","F"
3,"G","H"

in output i need like

Code:

3,"G","H"
1,"E","F"
2,"C","D"
1,"A","B"

that is what ever records in my file i need to reverse the order of rows as in the input. please give any pointers to this logic
regards
angel

Try:

Code:

tac infile

thanku so muchh


worked wellll

If tac is not available, one method is to keep the lines in memory in reverse order and then print them at the last line. For example:

Code:

awk '{p=$0 RS p} END{printf "%s",p}' infile

or

Code:

sed -n '1!G;h;$p' infile

tac is working fine .but i will try the above code also

Pls explain this part {p=$0 RS p} and how the lines are stored in the awk memory..

p is a variable. RS="\n". On the first line p becomes the firs line followed by a "\n". Every next line gets put at the beginning of p with a "\n" in between. At the end the variable p is printed except for the superfluous trailing "\n" that was put there on line 1.

We could also keep the newline out of the string on line 1, for example

Code:

awk '{p=$0((p)?RS p:x)} END{print p}' infile

where x has the value ""