PDF Text Processing – How to Get Page Numbers of a Pattern in PDF

$ sed ':again;$!N;$!b again; s/{[^}]*}//g' file
This is 
that wants
 anyway.

Explanation:

• :again;$!N;$!b again;

  This reads the whole file into the pattern space.

  :again is a label. N reads in the next line. $!b again branches back to the again label on the condition that this is not the last line.

• s/{[^}]*}//g

  This removes all expressions in braces.

On Mac OSX, try:

sed -e ':again' -e N -e '$!b again' -e 's/{[^}]*}//g' file

Nested Braces

Let's take this as a test file with lots of nested braces:

a{b{c}d}e
1{2
}3{
}
5

Here is a modification to handle nested braces:

$ sed ':again;$!N;$!b again; :b; s/{[^{}]*}//g; t b' file2
ae
13
5

Explanation:

• :again;$!N;$!b again

  This is the same as before: it reads in the whole file.

• :b

  This defines a label b.

• s/{[^{}]*}//g

  This removes text in braces as long as the text contains no inner braces.

• t b

  If the above substitute command resulted in a change, jump back to label b. In this way, the substitute command is repeated until all brace-groups are removed.

A buffer of lines needs to be used.

Give a try to this:

awk -v N=4 -v pattern="example.*pattern" '{i=(1+(i%N));if (buffer[i]&& $0 ~ pattern) print buffer[i]; buffer[i]=$0;}' file

Set N value to the Nth line before the pattern to print.

Set patternvalue to the regex to search.

buffer is an array of N elements. It is used to store the lines. Each time the pattern is found, the Nth line before the pattern is printed.