Question

I am using the preprocessor of gcc to remove the comments from a verilog (.v) file (since the comment syntax is same as C/C++). I am using perl and hence used a shell command from my perl script

gcc -E $dest > $commentsrem

where $dest is my verilog file renamed as a .c file.
Since the preprocessor outputs data onto stdout, I redirected it to a file named $commentsrem .
Now the problem I face is that I get messages on the terminal saying

try.c:577: unterminated character constant

I guess this is because although in C you need to use ‘\’ to continue a statement on a new line, verilog has no such requirement. That is what it is reporting.

Now although in spite of these, it achieves what I want, it’s making the terminal messy. Any way to keep it quiet?

Answer 1

Redirecting standard error to the null device would silence all error output from the preprocessor. Not generally recommended, as you will not see genuine errors either.

gcc -E $dest > $commentsrem 2> /dev/null

The better way would be to filter known messages from the stderr by use of grep -v, so you would still see other error messages. For this, you need to redirect stderr to stdout, because piping doesn’t work on stderr:

gcc -E $dest 2>&1 > $commentsrem | grep -v "unterminated character constant"

The order of the redirections is important here. If you wrote > $commentsrem 2>&1, the error messages would end up in $commentsrem instead.

For details on the redirecting, ref. this Q/A.