Ubuntu – How to find out how many files ending in .c or .cpp inside a directory contain the string: string

One possible way might be to replace grep by pcregrep (available from the 'universe' repository), which supports multiline matches, and then instead of searching for the literal string

Time series prediction with ensemble models

search instead for the perl compatible regular expression (PCRE)

Time\s+series\s+prediction\s+with\s+ensemble\s+models

where \s+ stands for one or more whitespace characters (including newlines). Using the bash shell's built-in string substitution capabilities to perform the latter step

pdftotext "$file" - | pcregrep -M "${string// /\\s+}"

If you can't use pcregrep then you might be able to get the output you want using plain grep with the -z switch: this tells grep to consider the input "lines" to be delimited by NUL characters rather than newlines - in this case, effectively making it treat the whole input as a single line. So for example if you only want to print the matches (without context)

pdftotext "$file" - | grep -zPo "${string// /\\s+}"

You can do it with grep only (without using find):

grep --include=\*.{xml,py} -Rl ./ -e "Jason"

And to exclude .po:

grep --exclude=*.po --include=\*.{xml,py} -Rl ./ -e "Jason"