r - how to delete the end of "}" and append three rows contents -

a.txt contents:

{\aaa {\bbb\ccc} {\aaa \bbb \ccc }  } 

i can load text in r using readlines (or scan). want know how delete end of "}" , append 3 rows contents:

\ddd \eee \fff 

then save new file. thank you.

i'm assuming want add new lines main block. if that's case,

lines<-scan(what=character(), text="{\\aaa {\\bbb\\ccc} {\\aaa \\bbb \\ccc }  } ") morelines<-append(lines, c("\\ddd","\\eee","\\fff"), after=length(lines)-1) writelines(morelines, "out.txt") 

should work.