[R] fgrep with caret (^) meta-character in system() call

[Ken]

man awk? 
I've used awk for similar tasks (if I am reading the post correctly.) Google-Fu should turn up some useful examples.
Also awk should be on your linux installation in some form or another.
Regards,
    Ken Hutchison

On Oct 4, 2554 BE, at 10:52 PM, "Tom D. Harray" <tomdharray at gmail.com> wrote:

> Hi there,
> 
> I would like to use my linux system's fgrep to search for a text pattern
> in a file. Calling system with
> 
>    system("fgrep \"SearchPattern\" /path/to/the/textFile.txt")
> 
> works in general, but I need to search for the search pattern at the
> beginning of the line.
> 
> The corresponding shell command
> 
>    fgrep "^SearchPattern" /path/to/the/textFile.txt
>               |
>               |___ here's my problem
> 
> does exactly what I want. I tried various combinations on ", \", \^, but
> failed to make system() work.
> 
> How can I call the working shell command including the caret
> meta-character with system()?
> 
> Thanks and regards,
> 
> dirk
> 
> 
> P.S.: Actually I have to search for about 5.000 patterns, stored in an R
> list, in a text file with about 30.000.000 lines. The patterns appear in
> one or 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.
> 
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