UNIX for Dummies Questions & Answers

Thanks a lot guys

---------- Post updated at 12:44 PM ---------- Previous update was at 08:57 AM ----------

ANd one more doubt guys y is that we have 1 after every completeion awk command andf before the inputfile

That '1' at the end refers to print line.

See these examples to get a clearer picture:

Code:

$ cat input
earth
hello
world
mars
$
$ ### If line contains "hello", replace "ll" with "LL" and print all lines
$ awk '/hello/ {sub(/ll/, "LL", $0)}{print}' input
earth
heLLo
world
mars
$
$ ### Same thing with 1 at the end
$  awk '/hello/ {sub(/ll/, "LL", $0)}'1 input
earth
heLLo
world
mars
$
$ ### If line contains "hello", replace "ll" with "LL" and print only that line. (Observe where print is placed here)
$ awk '/hello/ {sub(/ll/, "LL", $0); print}' input
heLLo

With "doubt" you mean "question", right? Bala could have put the 1 inside the single quotes, which is usually done, it does not matter. Everything in awk has the form condition{action}. If the condition evaluates to 1 then the action is performed. If the condition is omitted then the action is always performed. If the action is omitted then the default action in awk is performed, which is {print $0}. In this case the condition is "1" so that evaluates to 1 and the action is omitted, therefore {print $0} is performed, which is print the entire record.

@balajesuri, #2 will print matching lines twice on the same line...

Is it this one??

Code:

awk '/hello/ {sub(/ll/, "LL", $0)}'1 input

No I mean this one:

Ah yes, you're right. Didn't notice that. Silly typo