Shell Programming and Scripting

I have a irritating problem with a "if"-statement or what you should call it, in sed. I would love some help here since I am very, very stuck.

I have this statement that I want to do:
if line contains a:
do this
if none of the lines contained a:
do this

The problem with this statement is that I cant find out if it's possible and if so, how to implement this statement. In any case I've found, both "do this" will be made and I will get two outputs.


I've tried things such as:
"/searchstring/b ifpart"
"1s/^/<!-- ELSE -->/"
"b end"
":ifpart"
"s/searchstring\1<!-- IF -->/"
":end"

The problem is that in any case, the "ELSE" comment will be printed and if the searchstring is found, the IF comment will be printed as well. I only want ONE of them simultaniously, not both. I would really love to hear if it's possible or not and if you have any clue how to do it as well

Thank you!

That's not a job for sed; use the shell:

Code:

sstr=a
found=0

while IFS= read -r line
do
   case $line in 
     *"$sstr"*) : do whatever; found=1 ;;
   esac
done < file

if [ $found -eq 0 ]
then
  : do something else
fi

I have to use sed, whether its a job for it or not.

it's an application where sed commands are the only option, which means that I just have to solve it some way:/

If sed is the only option this sounds like coursework. Why are you restricted to sed only?

Because I'm using the mod_sed's Outputsed-directive in apache.. This do mean that I only have that option, right? :P

We have a rule against homework, no rule against torturing sed into something it was not meant for.

you can if then else in sed but it is plain ugly... work thru this:

http://student.northpark.edu/pemente/sed/ifelse.txt

haha

I know that it's a bit weird to try what I do, but I just want to atleast try to see how it performs.

Thanks for that link, and I did try those if/elses, but the problem is that it works line by line (as it should, but thats the problem!) which means that it won't work for me. I want to see if a string was found in the ENTIRE document, not only if it contains on line by line basis.

(Thats an edit from the previously mentioned pseudo I had, since I didn't know I would get this problem)

If the string is found in the entire document:
do this
else
do this

I'm beginning to believe that its not possible so I guess this is my last attempt. I would love to test this solution as it will solve a big problem for me.