I am very new to lex. I am trying to develop a parser to search a count of specific word in an given input file...
My code is
%{
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
int lnum = 1, fresult = 0, cc=0, wc=0, lc=0, bc=0, sc=0, nc=0, tc=0, result;
char temp[20], str[20], fname[20];
FILE *fp;
#undef yywrap
%}
digit[0-9]+
word [a-zA-Z]+
eol [\n]
blank [ ]
tab [\t]
result [word]
%%
{result} {
if((strstr(temp, str)) != 0)
{
printf(" A match found on line: %d\n", lnum);
fresult++;
wc++;
cc+=yyleng;
}
lnum++;
if(fresult == 0)
{
printf(" Match not found\n");
}
}
{digit} {nc++;}
{word} {wc++; cc+=yyleng;}
{tab} {tc++;}
{blank} {bc++;}
{eol} {lc++;}
. sc++;
%%
int main(int argc, char *argv[])
{
strcpy(fname,argv[1]);
strcpy(str,argv[2]);
fp=fopen(fname,"r+");
yyin=fp;
yylex();
printf(" Total count of the word is :%d\n", fresult);
printf(" Character Count = %d\n", cc);
printf(" Number Count = %d\n", nc);
printf(" Word Count = %d\n", wc);
printf(" Line Count = %d\n", lc);
printf(" Special Character Count = %d\n", sc);
printf(" Blank Count = %d\n", bc);
printf(" Tab Count = %d\n", tc);
return(0);
}
int yywrap()
{
return -1;
}
The word count and others are working perfectly.... But the word search is taking the input but not given the specific count...... How can I improve the code? Should I need to add anything?
Thanks in Advance...... :)
I have made some changes to your code to help you in the right direction. First, I created a variable to keep track of whether a match is found or not.
Secondly, I am not using strstr() anymore and instead I am using strcmp() because you want to match a word to a word not a word within a sentence and we do not need a pointer returned. strcmp() is nice because we just get an integer.
I see what you were trying to do with result [word] however, as you found out, this will not work. This section of the Flex file is known as the rules section. Here you use the regular expressions that you defined in the above section (definitions) to tell Flex what to do when a rule is matched.
As you can see, I have deleted all occurrences of result[word] - as this will not work. In the rules section, I also deleted the result definition because we no longer have a rule to match it. However, I keep the code for the result definitions and simply apply it to the word definition.
The last major change is adding the <<EOF>> rule which is a special rule that tells Flex what to do when it has encountered the end of the file. In our case, if the match variable is not 1, then we have not found a match and we would like to print this to the screen. We also need to call yyterminate() (definition at the bottom of the page) to stop the lexical analyzer.
Below is the updated code. I hope that helps!
%{
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
int lnum = 1, fresult = 0, cc=0, wc=0, lc=0, bc=0, sc=0, nc=0, tc=0, result;
char temp[20], str[20], fname[20];
FILE *fp;
int match = 0;//For keeping track of matches
#undef yywrap
%}
/*Rules*/
digit [0-9]+
word [a-zA-Z]+
eol [\n]
blank [ ]
tab [\t]
/*Definitions*/
%%
{digit} {
nc++;
}
{tab} {
tc++;
}
{blank} {
bc++;
}
{eol} {
lc++;
}
{word} {
if((strcmp(yytext, str)) == 0)//We found a match
{
printf("\n A match found on line: %d\n", lnum);
fresult++;
wc++;
cc+=yyleng;
match = 1;//We have a match
}
else //We found a word, but it was not a match
{
wc++;
}
}
. {
sc++;
}
<<EOF>> {
if(!match)
{
printf(" Match not found\n");
}
yyterminate();
}
%%
int main(int argc, char *argv[])
{
strcpy(fname,argv[1]);
strcpy(str,argv[2]);
fp = fopen(fname,"r+");
yyin = fp;
yylex();
printf("\n\n Total count of the word is :%d\n", fresult);
printf(" Character Count = %d\n", cc);
printf(" Number Count = %d\n", nc);
printf(" Word Count = %d\n", wc);
printf(" Line Count = %d\n", lc);
printf(" Special Character Count = %d\n", sc);
printf(" Blank Count = %d\n", bc);
printf(" Tab Count = %d\n", tc);
fclose(fp);
return(0);
}
int yywrap()
{
return 1;
}