Re: [Tinycc-devel] RFC: TCC Shell Programming

[ZHAO Wei]

That is more complicated. And has no benefits than plain shell
programming.

On Fri, 2003-06-20 at 15:53, Fabrice Bellard wrote:
> You could write small library to simulate pipes inside tcc by using 
> threads or fork().
> 
> Fabrice.
> 
> ZHAO Wei wrote:
> > Hello, this is a Request For Comments about a procedure to further
> > enable TCC to do Shell Programming. I came upon this idea when preparing
> > my second article in a series for IBM developerWorks/China to introduce
> > TCC. The article is in Chinese, so I rewrite the main idea here in
> > English.
> > 
> > The key to shell programming is the pipe. Concering pipe usage, there
> > are two things. One is to let TCC the compiler itself to cooperate with
> > other tools using pipes. Two is to let programs written for TCC to
> > cooperate using pipes.
> > 
> > TCC the compiler itself can use pipes with help from /dev/stdin. Though
> > it's not perfect, but enough for us now. Thanks to previous Tinycc-devel
> > postings to let me know this. :)
> > 
> > Point two above is almost moot. Because any C program can use stdin and
> > stdout to cooperate with others utilizing pipes.
> > 
> > The disadvantage of the above method is that one has to launch a lot of
> > processes which is not cool. :) With TCC we can have another method.
> > 
> > Let's see the following example for a simple tac implementation:
> > 
> > --------8<--[tac.c]------
> > #define _GNU_SOURCE
> > #include <stdio.h>
> > #include <stdlib.h>
> > 
> > struct record {
> >         struct record *prev;
> >         char *line;
> > };
> > 
> > void tac(FILE *in, FILE *out)
> > {
> >         struct record *this;
> >         struct record *last;
> >         size_t len = 0;
> > 
> >         last = NULL;
> >         this = (struct record *) malloc(sizeof(struct record));
> >         this->line = NULL;
> >         while ((getline(&(this->line), &len, in)) != -1) {
> >                 this->prev = last;
> >                 last = this;
> >                 this = (struct record *) malloc(sizeof(struct record));
> >                 this->line = NULL;
> >         }
> >         if (this->line)
> >                 free(this->line);
> >         free(this);
> >         while (last) {
> >                 this = last;
> >                 last = this->prev;
> >                 fprintf(out, "%s", this->line);
> >                 if (this->line)
> >                         free(this->line);
> >                 free(this);
> >         }
> > }
> > 
> > #ifdef STANDALONE
> > int main(int argc, char **argv)
> > {
> > /*      FILE *pipe; */
> > 
> > /*      pipe = tmpfile(); */
> > /*      tac(stdin, pipe); */
> > /*      fseek(pipe, 0, SEEK_SET); */
> > /*      tac(pipe, stdout); */
> > /*      fclose(pipe); */
> >         tac(stdin, stdout);
> >         return 0;
> > }
> > #endif /* STANDALONE */
> > -------->8--[tac.c]------
> > 
> > We can run tcc -DSTANDALONE -run tac.c to get a a standalone version for
> > tac. And if we want to utilizing tac() in a pipe series, we can just
> > call this function like we did above in the commented code, which is a
> > tac | tac. And the pipe combo utilizes only one process.
> > 
> > Do you like the idea? If there're enough interests, I can start building
> > a set of functions in the above manner. :) I only wrote few very simple
> > ones like the above for my article.
> > 
> > Please comment. Thanks a lot!
> > 
> 
> 
> 
> 
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-- 
ZHAO Wei
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http://www.advogato.org/person/zhaoway/
Linux & Free Software Consultant, Nanjing, China