Re: [Flex-help] flex and writing to file

[Chris v. <che...@gm...>]

fopen returns null on error, it's fprintf you have to check with "< 0".
 What about something like,

void printRTfront(char * txt){
  FILE *result = fopen("result","a+");
  if (!result) { printf("EEK!\n"); return; }
  if (fprintf(result, "%s", txt) < 0) { printf("EEEK!\n"); return; }
  if (fclose(result) != 0) { printf("EEEEK!\n"); return; }
}


I'm not the biggest fan of C.  :)

-Chris


On Tue, Aug 10, 2010 at 8:37 PM, Jeffrey Geyssens <jge...@gm...>wrote:

> Well,
>
> I've checked and I am able to write to any other file but result.
> I do write the result file before I want to write using flex.
> This is most-likely the cause of the trouble. My C knowledge is
> non-existent
> (do have some C++ knowledge though).
>
> [0-9]+ { yylval = atoi(yytext); return NUMBER; }
>
> "<"[^>]*> {
>  char cwd[1024];
>       if (getcwd(cwd, sizeof(cwd)) != NULL)
>           fprintf(stdout, "Current working dir: %s\n", cwd);
>       else
>           perror("getcwd() error");
>
> FILE *r;
> //r = fopen("result","a+");
> if (fopen("result", "a+") < 0)
>     fprintf(stderr, "Error: %s.\n", strerror(errno));
> else
> printf("A OK");
> //printf("%i",errno);
> //fprintf(r,"%s\n",yytext);
> //fclose(r);
>
> printf("%s\n",yytext);
> return COMMENT;}
>
> I get A OK so no errors..
>
> The procedure which wrote result file beforehand is:
> void printRTfront(char * txt){
>
> FILE *result;
> result = fopen("result","a+");
> fprintf(result,"%s", txt);
> fclose(result);
> }
>
> Must I flush something?
>
> 2010/8/11 Jeffrey Geyssens <jge...@gm...>
>
> > Well,
> >
> > I've checked and I am able to write to any other file but result.
> > I do write the result file before I want to write using flex.
> > This is most-likely the cause of the trouble. My C knowledge is
> > non-existent (do have some C++ knowledge though).
> >
> > [0-9]+ { yylval = atoi(yytext); return NUMBER; }
> >
> > "<"[^>]*> {
> >  char cwd[1024];
> >        if (getcwd(cwd, sizeof(cwd)) != NULL)
> >            fprintf(stdout, "Current working dir: %s\n", cwd);
> >        else
> >            perror("getcwd() error");
> >
> > FILE *r;
> > //r = fopen("result","a+");
> > if (fopen("result", "a+") < 0)
> >      fprintf(stderr, "Error: %s.\n", strerror(errno));
> > else
> > printf("A OK");
> > //printf("%i",errno);
> > //fprintf(r,"%s\n",yytext);
> > //fclose(r);
> >
> > printf("%s\n",yytext);
> > return COMMENT;}
> >
> > I get A OK so no errors..
> >
> > The procedure which wrote result file beforehand is:
> > void printRTfront(char * txt){
> >
> > FILE *result;
> > result = fopen("result","a+");
> > fprintf(result,"%s", txt);
> > fclose(result);
> > }
> >
> > Must I flush something?
> >
> >
> > 2010/8/11 Chris verBurg <che...@gm...>
> >
> >
> >> Did you check the error code on fopen?  Maybe you're out of file
> handles,
> >> or the disk is full, or you don't have write permissions, or blah blah
> blah.
> >>
> >> -Chris
> >>
> >>
> >>  On Tue, Aug 10, 2010 at 7:54 PM, Jeffrey Geyssens <jge...@gm...
> >wrote:
> >>
> >>>  Hello all,
> >>>
> >>> I have a noobish flex question, which has been consuming far to much
> >>> time.
> >>> I figured time to ask the experts.
> >>>
> >>> I have a flex file which contains the following rule:
> >>>
> >>> #include "stdio.h"
> >>> #include "yygrammar.h"
> >>> #include "unistd.h"
> >>>
> >>> "<"[^>]*> {
> >>>  char cwd[1024];
> >>>       if (getcwd(cwd, sizeof(cwd)) != NULL)
> >>>           fprintf(stdout, "Current working dir: %s\n", cwd);
> >>>       else
> >>>           perror("getcwd() error");
> >>>
> >>> FILE *result;
> >>> result = fopen("result","a+");
> >>> fprintf(result,"%s\n",yytext);
> >>> fclose(result);
> >>> printf("%s\n",yytext);
> >>> return COMMENT;}
> >>>
> >>> I want to print the working directory (to see where i am) and then
> write
> >>> yytext to a file.
> >>> The working directory is correct, and I assure you that result file is
> >>> located in this directory.
> >>>
> >>> I can print yytext to the screen using printf just fine.
> >>>
> >>> But I can't manage to print the yytext to the result file. The code is
> >>> copied from another part of the program, which works fine.
> >>> I'm starting to get scared... Please help
> >>>
> >>>
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> >>
> >>
> >
> >
> > --
> > met beleefde groeten
> > Jeffrey Geyssens
> >
>
>
>
> --
> met beleefde groeten
> Jeffrey Geyssens
>
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