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getchar()

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Join Date: Oct 2008

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tufzz

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getchar()

Oct 18th, 2008

I've been trying to read characters from the keyboard using 'getchar()' but my code always misses one character. Can anyone tell me why this is

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
int main(int argc, char *argv[]) {
 
	char string[50];
	int i;
	printf("Enter a string: ");
 
	for (i=0; i < strlen(string); i++){
		string[i] = getchar();
	}
 
	printf("%s", string);
}
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(int argc, char *argv[]) {

	char string[50];
	int i;
	printf("Enter a string: ");

	for (i=0; i < strlen(string); i++){
		string[i] = getchar();
	}

	printf("%s", string);
}

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Join Date: Dec 2005

Posts: 5,851

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Salem

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Void main'ers are DOOMed

Re: getchar()

Oct 18th, 2008

> for (i=0; i < strlen(string); i++)
You're lucky this works at all.
string starts off uninitialised, so who knows what strlen() on it will return.

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Join Date: Sep 2008

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Reputation: devnar will become famous soon enough

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devnar

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Re: getchar()

Oct 18th, 2008

string[i]=getchar(); I don't think this will work properly. getchar() expects you to hit enter after the input of each character which means that '\n' will be left in the input buffer which will be read the next time getchar() executes. Which means that each character will alternate with a '\n'.
I might be wrong though. Feel free to correct me.

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Join Date: Aug 2008

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grumpier

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Re: getchar()

Oct 18th, 2008

•

Originally Posted by devnar

string[i]=getchar(); I might be wrong though. Feel free to correct me.

You're wrong. getchar() does not behave in quite the way you described. Consider yourself corrected.

Salem is right. Once you get past the concern he pointed out, there are also additional problems that the code has no error checking, nor does it terminate the input string with a zero byte.

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Join Date: Sep 2008

Posts: 148

Reputation: devnar will become famous soon enough

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devnar

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Re: getchar()

Oct 18th, 2008

>You're wrong. getchar() does not behave in quite the way you described.

My bad. Did some research on getchar(). Seems getchar() doesn't need enter to be pressed after the input of each character. It can only see the input buffer after hitting the enter. Gotta get my basics straightened.

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Join Date: Sep 2008

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Sci@phy

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Re: getchar()

Oct 18th, 2008

It should be like this (yeah, I like writing nonesence):

 Help with Code Tags 
 c Syntax (Toggle Plain Text) 
int i = 0;
while ((string[i++] = getchar())!='\n');
string[i]='\0';
int i = 0;
while ((string[i++] = getchar())!='\n');
string[i]='\0';

•

Join Date: Oct 2008

Posts: 60

Reputation: HiHe is an unknown quantity at this point

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HiHe

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Re: getchar()

Oct 18th, 2008

You could do it like that:

 Help with Code Tags 
 c Syntax (Toggle Plain Text) 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
#define SIZE   50
 
int main(int argc, char *argv[]) {
 
	char string[SIZE], c;
	int i;
 
        // just a test
        printf("len = %d\n", strlen(string));  // len = 0
 
	printf("Enter a string: ");
 
	for (i=0; i < SIZE; i++){
                c = getchar();
                if (c == '\n'){
                    string[i] = '\0';
                    break;
                }
	    string[i] = c;
	}
 
	printf("string entered = %s", string);
}
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define SIZE   50

int main(int argc, char *argv[]) {

	char string[SIZE], c;
	int i;

        // just a test
        printf("len = %d\n", strlen(string));  // len = 0

	printf("Enter a string: ");

	for (i=0; i < SIZE; i++){
                c = getchar();
                if (c == '\n'){
                    string[i] = '\0';
                    break;
                }
	    string[i] = c;
	}

	printf("string entered = %s", string);
}

In C you can code our own bugs, in C++ you can inherit them.

•

Join Date: Dec 2005

Posts: 5,851

Reputation: Salem has a reputation beyond repute

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Salem

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Void main'ers are DOOMed

Re: getchar()

Oct 18th, 2008

> printf("len = %d\n", strlen(string)); // len = 0
Nope, read my first post again.
string isn't initialised, so your length is junk.
If you get zero, that just makes you lucky.

The rest is getting better though.

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Join Date: Jul 2008

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ahamed101

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Re: getchar()

Oct 18th, 2008

Just modifying Sci@phy's code...

 Help with Code Tags 
 c Syntax (Toggle Plain Text) 
	while ((string[i++] = getchar())!='\n' && i < SIZE);
	string[i]='\0';
	while ((string[i++] = getchar())!='\n' && i < SIZE);
	string[i]='\0';

This will do the trick...

regards,
Ahamed.

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Join Date: Jul 2008

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ahamed101

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Re: getchar()

#10

Oct 18th, 2008

•

Originally Posted by tufzz

I've been trying to read characters from the keyboard using 'getchar()' but my code always misses one character. Can anyone tell me why this is
Help with Code Tags

C Syntax (Toggle Plain Text)
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
int main(int argc, char *argv[]) {
 
	char string[50];
	int i;
	printf("Enter a string: ");
 
	for (i=0; i < strlen(string); i++){
		string[i] = getchar();
	}
 
	printf("%s", string);
}
#include <stdio.h> #include <stdlib.h> #include <string.h> int main(int argc, char *argv[]) { char string[50]; int i; printf("Enter a string: "); for (i=0; i < strlen(string); i++){ string[i] = getchar(); } printf("%s", string); }

This aint right...

 Help with Code Tags 
 c Syntax (Toggle Plain Text) 
	for (i=0; i < strlen(string); i++){
		string[i] = getchar();
	}
	for (i=0; i < strlen(string); i++){
		string[i] = getchar();
	}

strlen(string) will have some random number... you dont want that...

•

Originally Posted by Salem

> printf("len = %d\n", strlen(string)); // len = 0
Nope, read my first post again.
string isn't initialised, so your length is junk.
If you get zero, that just makes you lucky.

The rest is getting better though.

Salem is right...
String is uninitialised... you get junk for len... for sure...

•

Originally Posted by HiHe

You could do it like that:
Help with Code Tags

c Syntax (Toggle Plain Text)
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
#define SIZE   50
 
int main(int argc, char *argv[]) {
 
	char string[SIZE], c;
	int i;
 
        // just a test
        printf("len = %d\n", strlen(string));  // len = 0
 
	printf("Enter a string: ");
 
	for (i=0; i < SIZE; i++){
                c = getchar();
                if (c == '\n'){
                    string[i] = '\0';
                    break;
                }
	    string[i] = c;
	}
 
	printf("string entered = %s", string);
}
#include <stdio.h> #include <stdlib.h> #include <string.h> #define SIZE 50 int main(int argc, char *argv[]) { char string[SIZE], c; int i; // just a test printf("len = %d\n", strlen(string)); // len = 0 printf("Enter a string: "); for (i=0; i < SIZE; i++){ c = getchar(); if (c == '\n'){ string[i] = '\0'; break; } string[i] = c; } printf("string entered = %s", string); }

This is good... but it will take one junk character... try executing this code... and its a bit lengthy code for such an read operation...

better way...

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
while ((string[i++] = getchar())!='\n' && i < SIZE);
	string[i]='\0';
while ((string[i++] = getchar())!='\n' && i < SIZE);
	string[i]='\0';