grep regex to ignore comment at end of line?

Question

I'm trying to grep through a lot of old PowerBASIC source files in search of a variable, but I'm having trouble getting `grep` to avoid matching references to the variable in the end-of-line comments. For example: ANGLE = 40 ' THIS IS A COMMENT ABOUT ANGLE'S VALUE FOO = 3/ANGLE ' ANGLE CAN APPEAR ON RIGHT SIDE AS WELL DELTA = 35 ' ANGLE AND DELTA AREN'T FRIENDS Initially I was using: # grep "\\bANGLE\\b.*'" SRC_FILE.BAS But -- besides ignoring lines with no comments -- it also prints out lines of code which don't use `ANGLE` at all (such as the `DELTA` line). This is because those lines happen to also have a *single* apostrophe (`'`) in their comments (i.e. `AREN'T`). I thought of piping the output to remove the lines I don't want with: # grep "\\bANGLE\\b" SRC_FILE.BAS | grep -v "'.*\\bANGLE\\b" But unfortunately it also removes the lines of code I do want that just happen to have "`ANGLE`" in their comments. How do I get grep to match the lines of actual code involving `ANGLE` and ignore those lines with *only* matches in the comments?

Answer 1

So here's a notional script that matches your description:

ANGLE1 = 40

ANGLE2 = 50

GO TO 100 ## ANGLE2=256

IF X = 512 ...

## end of script

Let's use ANGLE2 as my example variable we're hunting for.

So I want the 2nd line above, but not the 3rd.

Maybe I'm missing something, but doesn't this do what you're looking for?

$ grep -in -e "angle2" script | grep -vi "#.*angle2"

2:ANGLE2 = 50

It does mean using a 2nd grep process, and avoiding that would be nice if you could ...

I was wondering if egrep can be used to avoid the pipline ...

The following would grab lines that match either ANGLE1 or ANGLE2

$ egrep -ni -e "ANGLE1" -e "ANGLE2" script

1:ANGLE1 = 40

2:ANGLE2 = 50

3:GO TO 100 ## ANGLE2=256

But can we ask egrep to match pattern1, except if pattern2 is in the mix?

Is there a regular-expression that would accomplish that?

I haven't found one yet, but will follow up here if I do