Question about Lex

[Ger Timmens]

gtir5 at fel.tno.nl (Ger Timmens) writes:

>This is what I do:

>1. lex lexcommands         /* ==> lex.yy.c */
>2. cc lex.yy.c             /* ==> a.out    */
>3. a.out < input > output  /* ==> output   */

>I've got the following problem:
>When I encounter a string in the file *input* I want to
>generate an error message reporting the line number and
>file.

[deleted text]

Here are the solutions:

The line number: use yylineno (a global Lex integer).

The file name:   instead of redirecting the input and output,
		 you use fixed file names. So

      3. a.out < input > output
becomes
      3. a.out input output
And you connect Lex's stdin and stdout (yyin and yyout) to these files:
So you get the following Lex file: (Thanks to you all) !!!!

-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

%{
	char	InFile[20];
	char	OutFile[20];
%}

%%
"string"	fprintf(stderr,"Found %s at line %d in file %s\n",
			yytext,yylineno,InFile);
%%


void main(int argc, char **argv)
{
	if (argc != 3)
	{
		fprintf(stderr,"Usage: %s <input-file>", argv[0]);
		fprintf(stderr," <ouput-file>\n");
		exit(1);
	}

	strcpy(InFile, argv[1]);
	strcpy(OutFile, argv[2]);
	yyin = fopen(InFile, "r");
	yyout = fopen(OutFile, "w");
	yylex();
	fclose(yyin);
	fclose(yyout);
}