You can pretty easily empirically test this and conclude that your impression is not true, at least for GNU grep. :-) $ time grep 'ZQZQZQZQZQ' OpenSubtitle

You can pretty easily empirically test this and conclude that your impression is not true, at least for GNU grep. :-) $ time grep 'ZQZQZQZQZQ' OpenSubtitles2018.raw.en | wc -l 0 real 1.089 user 0.230 sys 0.858 maxmem 5 MB faults 0 $ time grep -E 'ZQZQZQZQZQ' OpenSubtitles2018.raw.en | wc -l 0 real 1.094 user 0.210 sys 0.883 maxmem 5 MB faults 0 $ time grep -F 'ZQZQZQZQZQ' OpenSubtitles2018.raw.en | wc -l 0 real 1.096 user 0.223 sys 0.872 maxmem 5 MB faults 0