Executing Perl from R - perlQuote/shQuote? -

i'm trying run perl r using system: assigning string (provided in r) variable , echoing it. (the system call executes in /bin/sh)

echo <- function (string) {     cmd <- paste(shquote(sys.which('perl')),                  '-e',                  shquote(sprintf("$str=%s; print $str", shquote(string))))     message(cmd)     system(cmd) } # fine: # echo('hello world!') # echo("'") # echo('"') # echo('foo\nbar') 

however, if try echo backslash (or indeed string ending in backslash), error:

> echo('\\') '/usr/bin/perl' -e "\$str='\\'; print \$str" can't find string terminator "'" anywhere before eof @ -e line 1. 

(note: backslash in front of $ fine protects /bin/sh thinking $str shell variable).

the error because perl interpreting last \' embedded quote mark within $str opposed escaped backslash. in fact, perl echo backslash need do

> echo('\\\\') '/usr/bin/perl' -e "\$str='\\\\'; print \$str" \ # <-- prints 

that is, need escape backslashes perl (in addition me escaping them in r/bash).

how can ensure in echo string user enters string gets printed? i.e. level of escaping needed on r level?

i.e. there sort of perlquote function analagous shquote? should manually escape backslashes in echo function? there other characters need escape given?

don't generate code. that's hard. instead, pass argument argument:

echo <- function (string) {     cmd <- paste(shquote(sys.which('perl')),                  '-e', shquote('my ($str) = @argv; print $str;'),                  shquote(string))     message(cmd)     system(cmd) } 

(you use environment variable.)

(i've never used or seen r code before, pardon syntax errors.)