sed command line to change "aas=aas" into "aas = aas" - regex

Question

A Questions for the regular expression/ sed experts out there:
I need to beautify some c++ code.
The code is littered with various version of the assignment operator with different types of spacing.
i.e.
a=b
a =b
a= B
a = b
a= b
A = B. // the correct format needed, and so must be ignored by SED
There should only be one space around the =. If more are found, the extras must be removed.
I need to make a script that will scan through all files in folder and subfolders and search and replace as needed.
There are some variations, like the a+=b etc.
I run on OsX but have linux and windows machines available.
help much appreciated.

Answer 1

You can use this sed to insert a single space before and after all = operators:
Input file:
cat file
a ==b
a=b
a =b
a/=b
a *=b
a+= b
a-= b
a= B
a%= B
a = b
a= b
A = B
sed command:
sed -E 's~[[:blank:]]*([-+*/%=]?=)[[:blank:]]*~ \1 ~g' file
a == b
a = b
a = b
a /= b
a *= b
a += b
a -= b
a = B
a %= B
a = b
a = b
A = B
This is regex used for matching (using ~ as delimiter):
~[[:blank:]]*([-+*/%=]?=)[[:blank:]]*~ - matches 0 or more white spaces followed by an optional -+*/%= characters before a literal =. We are also capturing this operator in group #1
This is patter used in replacement:
~ \1 ~ Which means a space before and after string captured in group #1

Answer 2

It may interest you doing it with Perl
A simple file.cpp:
#include <iostream>
int main(){
int i = 3;
i += 3;
i-=3;
i * = 3; // not valid just for sure
i/=3;
int i2
=
3;
if( i
=
= i2 ){} // not valid just for sure
}
perl -lpe '$/=undef;s/\s*([=!%\*\/+-])?\s*(=)\s*/ $1$2 /g' file.cpp
the output:
#include <iostream>
int main(){
int i = 3;
i += 3;
i -= 3;
i *= 3;
i /= 3;
int i2 = 3;
if( i == i2 ){}
}