How to using sed in pipelines - bash

Question

I have file, and I need replace one word in it.
I can find this word with many grep's and pipelines.
cat file | <many times grep here>
for example:
>> cat test.cpp | grep -o "\-\-window [0-9]* \"" | grep -o "[0-9]*"
>> 71303214
How can i change result number in this pipeline?

Answer 1

You can use look-ahead and look-behind as follows:
grep -Po '(?<=\-\-window )\d*(?= \")' file
It looks for digits (\d*) in between a block of --window_ and _" (_ stands for space).
If you want to replace with sed, use:
sed 's/--window \([0-9]*\) \"/\1/g' file
It looks for --window_digits_* and replaces them with digits (_ stands for space).
Update
If you want to replace it with another number, do:
sed 's/--window [0-9]* \"/new_number/g' file
Or you can even use a bash variable if you use double quotes (with single, it wouldn't expand the variable).
sed "s/--window [0-9]* \"/$new_number/g" file
Test
$ cat a
hello --window 234234 " a
hello --window 234234a " a
hello this is another thing
$ grep -Po '(?<=\-\-window )\d*(?= \")' a
234234
$ sed 's/--window \([0-9]*\) \"/\1/g' a
hello 234234 a
hello --window 234234a " a
hello this is another thing
$ sed 's/--window [0-9]* \"/XXX/g' a
hello XXX a
hello --window 234234a " a
hello this is another thing
$ number=22
$ sed "s/\(--window \)[0-9]*\( \"\)/\1$number\2/g" a
hello --window 22 " a
hello --window 234234a " a
hello this is another thing

Answer 2

sed -n '/--window [0-9]* \"/ {
s/[^[:digit:]]//gp
}' file
sed with file as input (so no need of cat pipe before)
use of -n for not printing output unless specific request (P in command)
first pattern between // (regex reduced so you need to escape some meta char like \ / . *)
(here) extraction of digit by removing other char of the line and print the result if it occur
As you see, grep is better in this case (more readeable and efficient)

Answer 3

I THINK all you're asking for is:
$ cat file
#define CLICK(x,y) system("xdotool mousemove --window 71303214 " #x" "#y " click 1");
$ var="888999"; sed "s/\(.*--window \)[^ ]*/\1$var/" file
#define CLICK(x,y) system("xdotool mousemove --window 888999 " #x" "#y " click 1");
If that's not it, update your question to show some representative sample input and expected output.