Using sed, How to Insert a line at the beginning of a C function - closing paren, newline, opening curly brace - c

Question

I want to insert a line at the beginning of several C functions that are formatted the same. I suspect sed is the way to do this but I have limited sed knowledge. Thanks.
void func (any arbitrary list of parameters)
{
void func (any arbitrary list of parameters)
{
myNewInsertedLineHere

Answer 1

If the opening braces for functions begin on the first column and if they are the only braces that are in the first column (i.e. if you place opening braces for structs and enums at the end of a line), you can use:
sed -e 's/^{/{\n MYNEWLINE;/g' orig.c > edited.c
This seems to work in a quick test, but usual warnings and disclaimers apply.
Edit: As pointed out in the comments, not only functions have curly braces in the first column, so some context is needed. We can use another tool from the 70s, awk:
awk 'BEGIN {split("typedef union struct enum", a); \
for (i in a) skip[a[i]] = 1;}; \
{print; if (/^{/ && !(last in skip)) print " MYFIRSTLINE();"; \
if (NF > 0) last = $1; }' orig.c > edited.c
That's a one-liner in theory, but it might be better in a separate file, say first.awk:
#!/usr/bin/awk -f
BEGIN {
split("typedef union struct enum", a);
for (i in a) skip[a[i]] = 1;
};
{
print;
if (/^{/ && !(last in skip))
print " MYFIRSTLINE();";
if (NF > 0) last = $1;
}
Then you can call the script with
awk -f first.awk orig.c > edited.c
or, after chmodding executing permissions as
first.awk orig.c > edited.c
Of course, the same strategy:
print every line;
when there is a brace in the first column and the context isn't a type or variable definition, print the additional content;
save the first word to determine the context for the next line
can be implemented in any other scripting language, too.

Answer 2

A program is almost ever too complex for such simple rules. You said in title closing paren, newline, opening curly brace. What do you want to do with:
if testfunction(val)
{
It follows the criteria but is not a function definition.
That being said, the following sedscript should do the trick, it even cares for optional tabs or spaces around the {
/)[ \t\r]*$/ {
n
s/^[ \t]*}[ \t\r]*$/&/
t add
b end
:add
a\
\
end
}
In english, it reads:
look for a line ending with right paren
look at next line
try to replace a line containing only an opening curly brace (apart from white spaces) by itself
if substitution matched add an empty line