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Oct 18th, 2008

getchar()

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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

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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tufzz

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Oct 18th, 2008

Re: getchar()

> 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.

Salem

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Oct 18th, 2008

Re: getchar()

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.

devnar

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Oct 18th, 2008

Re: getchar()

Click to Expand / Collapse Quote 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.

grumpier

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Oct 18th, 2008

Re: getchar()

>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.

devnar

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Oct 18th, 2008

Re: getchar()

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

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';

Sci@phy

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Oct 18th, 2008

Re: getchar()

You could do it like that:

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);
}

HiHe

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Oct 18th, 2008

Re: getchar()

> 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

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Oct 18th, 2008

Re: getchar()

Just modifying Sci@phy's code...

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...

ahamed101

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Oct 18th, 2008

Re: getchar()

Click to Expand / Collapse Quote 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
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...

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...

Click to Expand / Collapse Quote 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...

Click to Expand / Collapse Quote originally posted by HiHe ...

You could do it like that:
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...

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';

ahamed101

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