Question

I’m trying to do a bit of group matching using sed.

Basically I have something like this:

func_name(4234,43543,76,1)

And I need to match the parameters of the function:

$ echo 'func_name(4234,43543,76,1)' | sed -n 's/\([0-9][0-9]*\).*/\1 /p' 
func_name(4234 

$ echo 'func_name(4234,43543,76,1)' | sed -n 's/\([[:digit:]]+\).*/\1 /p'
<empty>

$  echo 'func_name(4234,43543,76,1)'| sed -n 's/.*\([0-9][0-9]*\).*/\1 /p' 
1 

Answer 1

If you know the number of parameters and they are always ‘simple’ (no nested parentheses and hence no embedded commas either), then:

echo "func_name(4234,53543,76,1)" |
sed 's/.*(\([^,)]*\),\([^,)]*\),\([^,)]*\),\([^,)]*\))/a1 \1; a2 = \2; a3 = \3; a4 = \4/'

Note that this tolerates spaces after the commas (and before them too – but you wouldn’t leave spaces before, would you?).

Or, if the parameters are simple unsigned integers and you know the function name, maybe:

echo "func_name(4234,53543,76,1)" |
sed 's/func_name(\([0-9]*\), *\([0-9]*\), *\([0-9]*\), *\([0-9]*\))/a1 \1; a2 = \2; a3 = \3; a4 = \4/'

To get all the parameters in a single match, you have to do nested grouping:

echo "func_name(4234,53543,76,1)" |
sed 's/func_name(\(\([0-9]*\), *\([0-9]*\), *\([0-9]*\), *\([0-9]*\)\))/args = \1/'

Now \2 .. \5 still refer to the separate arguments.

echo "func_name(4234,53543,76,1)" |
sed 's/func_name(\(\([0-9]*\)\(, *\([0-9]*\)\)\{3\}\))/args = \1/'

This uses the repeat control \{3\} to find the arguments after the first.