search for: aaaooooooooooo

...more lines of the text file. Only those lines have to be extracted if the patterns at the beginning of the line. Example with matching line 1, non matching line 2, non-matching line 3 (line three comprises aaa, but not at the beginning of the line 3): SearchPattern = "^aaa" Text file: aaaooooooooooo bbbiiiiiiiiiii aacttttttttaaa Going line by line through the file in R is too slow, and I cannot program it in C or C++. Hence I use the fgrep command. I would appreciate if anyone has a fast alternative which works with R on Linux and Windows systems.