I have written a simple program to count number of vowels and consonants in LEX. But the program does not terminate after I enter input and enters an infinite loop. Here's the program
%{
#include<stdio.h>
int vow_count = 0;
int const_count = 0;
%}
%%
[aeiouAEIOU] {vow_count++;}
[a-zA-Z] {const_count++;}
%%
int yywrap(){return 1;}
int main()
{
printf("Enter a string : ");
yylex();
printf("\n No. of vowels = %d", vow_count);
printf("\n No. of consonants = %d\n", const_count);
return 0;
}
Here's the output
I have tried almost everything, I have tried with "%option noyywrap", without the yywrap() function.
Also the the program works fine when I take input from a file.
Use getch(); after the last printf statement in the main function. Also, after giving your input in the command prompt, press Ctrl+Z. I'm using Windows, it worked for me.
You have to press ctrl + d to terminate.
After pressing ctrl + d you will get the below output.
Related
Whenever I try to run the following code to count my characters I constantly get zero instead of the number of characters I have inserted.
#include <stdio.h>
void main() {
int c;
int count = 0;
while ( (c = getchar() != EOF) && c == 'a' ) {
count = count +1;
}
printf("Number of chara: %d", count);
}
I have altered the code to instead only count whenever 'a' comes up, but still only get zero when I enter my characters and hit the return key.
The condition of your while loop evaluates to false when the program reads a character that isn't an 'a', which ends the while loop. Since your program reads characters in the while loop, no more characters get read.
Try checking if the character is an 'a' inside the loop body before updating the counter instead of in the loop condition.
The loop will stop because you set the c=='a'. Try to remove that in your code.
Try this one:
int c;
int count = 0;
while (c = getchar() != EOF ) {
count = count +1;
}
printf("Number of chara: %d", count);
}`
I have created a file 'meta.dat' in my current directory and want the code below to give me this output
The character B
Number of items read 1
int main() {
FILE* fp = fopen("meta.dat", "wb");
char j = 'B';
fwrite(&j, sizeof(j), 1, fp);
fclose(fp);
FILE* fp1 = fopen("meta.dat", "rb");
char i = '\0';
int n = fread(&i, sizeof(i), 1, fp1);
printf("The character %c\n", &i);
printf("Number of items read %d\n", &n);
}
However what I get is this output in my console (I use Windows):
The character &
Number of items read 6422304
What's wrong with the code? And what's happening behind the scenes, why am I seeing this strange output?
This may be a simple question, but I'm new to C, and yet couldn't find any answer. My program is simple, it takes 21 lines of string input in a for loop, and print them after that. The number could be less or greater.
int t = 21;
char *lines[t];
for (i = 0; i < t; i++) {
lines[i] = malloc(100);
scanf("%s", lines[i]);
}
for (int i = 0; i < t; i++) {
printf("%s\n", lines[i]);
free(lines[i]);
}
...
So when I copy & paste the inputs at a time, my program hangs, no error, no crash. It's fine if there's only 20 lines or below. And if I enter by hand line by line, it works normally regardless of number of inputs.
I'm using XCode 5 in Mac OS X 10.10, but I don't think this is the issue.
Update:
I tried to debug it when the program hangs, it stopped when i == 20 at the line below:
0x7fff9209430a: jae 0x7fff92094314 ; __read_nocancel + 20
The issue may be related to scanf, but it's so confused, why the number 20? May be I'm using it the wrong way, great thanks to any help.
Update:
I have tried to compile the program using the CLI gcc. It works just fine. So, it is the issue of XCode eventually. Somehow it prevents user from pasting multiple inputs.
Use fgets when you want to read a string in C , and see this documentation about that function:
[FGETS Function]
So you should use it like this :
fgets (lines[i],100,stdin);
So it'll get the string from the input of the user and you can have a look on these two posts as well about reading strings in C:
Post1
Post2
I hope that this'll help you with your problem.
Edit :
#include <stdio.h>
void main(){
int t = 21;
int i;
char *lines[t];
for (i = 0; i < t; i++) {
lines[i] = malloc(100);
fgets(lines[i],255,stdin);
}
for (i = 0; i < t; i++) {
printf("String %d : %s\n",i, lines[i]);
free(lines[i]);
}
}
This code gives :
As you can see , I got the 21 strings that I entered (From 0 to 20, that's why it stops when i==20).
I tried with your input ,here's the results :
I wrote the same code and ran. It works.
It might contain more than 99 characters (include line feed) per line...
Or it might contain spaces and tabs.
scanf(3)
When one or more whitespace characters (space, horizontal tab \t, vertical tab \v, form feed \f, carriage return \r, newline or linefeed \n) occur in the format string, input data up to the first non-whitespace character is read, or until no more data remains. If no whitespace characters are found in the input data, the scanning is complete, and the function returns.
To avoid this, try
scanf ("%[^\n]%*c", lines[i]);
The whole code is:
#include <stdio.h>
int main() {
const int T = 5;
char lines[T][100]; // length: 99 (null terminated string)
// if the length per line is fixed, you don't need to use malloc.
printf("input -------\n");
for (int i = 0; i < T; i++) {
scanf ("%[^\n]%*c", lines[i]);
}
printf("result -------\n");
for (int i = 0; i < T; i++) {
printf("%s\n", lines[i]);
}
return 0;
}
If you still continue to face the problem, show us the input data and more details. Best regards.
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;
}
{result} {
if((strstr(temp, str)) != 0)
result [word]
Result is a regex for the characters 'w', 'o', 'r', 'd', which is not what you want. You probably want to match on {word}. In addition, temp will always be null - I think you want to use yytext instead.
I have always wondered how people update a previous line in a command line. a great example of this is when using the wget command in linux. It creates an ASCII loading bar of sorts that looks like this:
[======> ] 37%
and of course the loading bar moves and the percent changes, But it doesn't make a new line. I cannot figure out how to do this. Can someone point me in the right direction?
One way to do this is to repeatedly update the line of text with the current progress. For example:
def status(percent):
sys.stdout.write("%3d%%\r" % percent)
sys.stdout.flush()
Note that I used sys.stdout.write instead of print (this is Python) because print automatically prints "\r\n" (carriage-return new-line) at the end of each line. I just want the carriage-return which returns the cursor to the start of the line. Also, the flush() is necessary because by default, sys.stdout only flushes its output after a newline (or after its buffer gets full).
There are two ways I know of to do this:
Use the backspace escape character ('\b') to erase your line
Use the curses package, if your programming language of choice has bindings for it.
And a Google revealed ANSI Escape Codes, which appear to be a good way. For reference, here is a function in C++ to do this:
void DrawProgressBar(int len, double percent) {
cout << "\x1B[2K"; // Erase the entire current line.
cout << "\x1B[0E"; // Move to the beginning of the current line.
string progress;
for (int i = 0; i < len; ++i) {
if (i < static_cast<int>(len * percent)) {
progress += "=";
} else {
progress += " ";
}
}
cout << "[" << progress << "] " << (static_cast<int>(100 * percent)) << "%";
flush(cout); // Required.
}
The secret is to print only \r instead of \n or \r\n at the and of the line.
\r is called carriage return and it moves the cursor at the start of the line
\n is called line feed and it moves the cursor on the next line
In the console. If you only use \r you overwrite the previously written line.
So first write a line like the following:
[ ]
then add a sign for each tick
\r[= ]
\r[== ]
...
\r[==========]
and so on.
You can use 10 chars, each representing a 10%.
Also, if you want to display a message when finished, don't forget to also add enough white chars so that you overwrite the previously written equal signs like so:
\r[done ]
below is my answer,use the windows APIConsoles(Windows), coding of C.
/*
* file: ProgressBarConsole.cpp
* description: a console progress bar Demo
* author: lijian <hustlijian#gmail.com>
* version: 1.0
* date: 2012-12-06
*/
#include <stdio.h>
#include <windows.h>
HANDLE hOut;
CONSOLE_SCREEN_BUFFER_INFO bInfo;
char charProgress[80] =
{"================================================================"};
char spaceProgress = ' ';
/*
* show a progress in the [row] line
* row start from 0 to the end
*/
int ProgressBar(char *task, int row, int progress)
{
char str[100];
int len, barLen,progressLen;
COORD crStart, crCurr;
GetConsoleScreenBufferInfo(hOut, &bInfo);
crCurr = bInfo.dwCursorPosition; //the old position
len = bInfo.dwMaximumWindowSize.X;
barLen = len - 17;//minus the extra char
progressLen = (int)((progress/100.0)*barLen);
crStart.X = 0;
crStart.Y = row;
sprintf(str,"%-10s[%-.*s>%*c]%3d%%", task,progressLen,charProgress, barLen-progressLen,spaceProgress,50);
#if 0 //use stdand libary
SetConsoleCursorPosition(hOut, crStart);
printf("%s\n", str);
#else
WriteConsoleOutputCharacter(hOut, str, len,crStart,NULL);
#endif
SetConsoleCursorPosition(hOut, crCurr);
return 0;
}
int main(int argc, char* argv[])
{
int i;
hOut = GetStdHandle(STD_OUTPUT_HANDLE);
GetConsoleScreenBufferInfo(hOut, &bInfo);
for (i=0;i<100;i++)
{
ProgressBar("test", 0, i);
Sleep(50);
}
return 0;
}
PowerShell has a Write-Progress cmdlet that creates an in-console progress bar that you can update and modify as your script runs.
Here is the answer for your question... (python)
def disp_status(timelapse, timeout):
if timelapse and timeout:
percent = 100 * (float(timelapse)/float(timeout))
sys.stdout.write("progress : ["+"*"*int(percent)+" "*(100-int(percent-1))+"]"+str(percent)+" %")
sys.stdout.flush()
stdout.write("\r \r")
As a follow up to Greg's answer, here is an extended version of his function that allows you to display multi-line messages; just pass in a list or tuple of the strings you want to display/refresh.
def status(msgs):
assert isinstance(msgs, (list, tuple))
sys.stdout.write(''.join(msg + '\n' for msg in msgs[:-1]) + msgs[-1] + ('\x1b[A' * (len(msgs) - 1)) + '\r')
sys.stdout.flush()
Note: I have only tested this using a linux terminal, so your mileage may vary on Windows-based systems.
If your using a scripting language you could use the "tput cup" command to get this done...
P.S. This is a Linux/Unix thing only as far as I know...