While working on a tcl implementation of a cpp (i.e. C preprocessor) I found it necessary to splice together lines with escaped new lines while preserving the line number where the splice began.
Given a file of source lines that look like the following.
line(1) line(2)\ line(3) with space after excape\ line(4)\ line(5) line(6)\ line(7) line(8)
This code ...
set fid [open [file normalize "./filename"] r]
set text [read ${fid}]
close $fid
regsub -all -- {[\\][ \t]*[\n]} ${text} "\\\n" text
while { [regsub -all -- {[\\][\n](.*?[^\\])[\n]} ${text} "\\1\n\n" text] } {}produces the following results (line number were added).
| no. | output | |
|---|---|---|
| 1 | line(1) | 2|line(2)line(3) with space after excapeline(4)line(5) |
| 3 | ||
| 4 | ||
| 5 | ||
| 6 | line(6)line(7) | |
| 7 | ||
| 8 | line(8) |
Notice that the lines have been spliced together and the spliced lines occur on the correct line in the output.