echo charecter program...

[hdsalbki]

hi everyone,
I have below a small program to echo back what character the user
types. It's working OK but prints a extra prompt between every
character. what can I do? I'm new in C and my book is very
difficult...
thanks for any help.

#include<stdio. h>

main()
{
char a;
while(1)
{
printf("\nPleas e type a character: ");
scanf("%c",&a);
printf("\nYou typed: %c",a);
}
}

[vippstar]

On Jul 13, 1:10 pm, hdsalbki <hdsal...@gmail .comwrote:

hi everyone,
I have below a small program to echo back what character the user
types. It's working OK but prints a extra prompt between every
character. what can I do? I'm new in C and my book is very
difficult...
thanks for any help.

#include<stdio. h>

A space here would not be bad,
#include <stdio.h>
Note that both are valid, but the former is considered bad style by
some.

main()

Change that to int main(void)

{
char a;
while(1)
{
printf("\nPleas e type a character: ");

You should fflush(stdout); after that printf().

scanf("%c",&a);

You should check the return value of scanf().

printf("\nYou typed: %c",a);
}

}

Here is the fix:

#include <stdio.h>

int main(void) {

char c;

while(1) {
printf("Please type a character: ");
fflush(stdout);
if(scanf("%c%*[^\n]%*c") < 1) break;
printf("You typed: %c\n", a);
}

return 0;
}

[Joachim Schmitz]

vi******@gmail. com wrote:

On Jul 13, 1:10 pm, hdsalbki <hdsal...@gmail .comwrote:

>hi everyone,
I have below a small program to echo back what character the user
types. It's working OK but prints a extra prompt between every
character. what can I do? I'm new in C and my book is very
difficult...
thanks for any help.

#include<stdio .h>

A space here would not be bad,
#include <stdio.h>
Note that both are valid, but the former is considered bad style by
some.

>main()

Change that to int main(void)

>{
char a;
while(1)
{
printf("\nPleas e type a character: ");

You should fflush(stdout); after that printf().

> scanf("%c",&a);

You should check the return value of scanf().

> printf("\nYou typed: %c",a);
}

}

Here is the fix:

not quite

#include <stdio.h>

int main(void) {

char c;

while(1) {
printf("Please type a character: ");
fflush(stdout);
if(scanf("%c%*[^\n]%*c") < 1) break;

if(scanf("%c%*[^\n]%*c", &c) < 1) break;

printf("You typed: %c\n", a);

printf("You typed: %c\n", c);

}

return 0;
}

Bye, Jojo

[hdsalbki]

vipps...@gmail. com wrote:

On Jul 13, 1:10 pm, hdsalbki <hdsal...@gmail .comwrote:

hi everyone,
I have below a small program to echo back what character the user
types. It's working OK but prints a extra prompt between every
character. what can I do? I'm new in C and my book is very
difficult...
thanks for any help.

#include<stdio. h>

A space here would not be bad,
#include <stdio.h>
Note that both are valid, but the former is considered bad style by
some.

main()

Change that to int main(void)

{
char a;
while(1)
{
printf("\nPleas e type a character: ");

You should fflush(stdout); after that printf().

scanf("%c",&a);

You should check the return value of scanf().

printf("\nYou typed: %c",a);
}

}

Here is the fix:

#include <stdio.h>

int main(void) {

char c;

while(1) {
printf("Please type a character: ");
fflush(stdout);
if(scanf("%c%*[^\n]%*c") < 1) break;
printf("You typed: %c\n", a);
}

return 0;
}

Thank you so much vippstar! I was really scratching my head with this
problem and my book said nothing about scanf() leaving the \n in
input. I will do the fixes you suggest but I just can't understand
your scanf() call after the "%c"...what do all those characters do?
can you please explain? thanks again.

[vippstar]

On Jul 13, 2:07 pm, hdsalbki <hdsal...@gmail .comwrote:

vipps...@gmail. com wrote:

<snip>

if(scanf("%c%*[^\n]%*c") < 1) break;

<snip>

Thank you so much vippstar! I was really scratching my head with this
problem and my book said nothing about scanf() leaving the \n in
input. I will do the fixes you suggest but I just can't understand
your scanf() call after the "%c"...what do all those characters do?
can you please explain? thanks again.

See Mr Schmitz correction on my post to get the correct source code.
%* means match conversion but do not "write" to object.
So %*d would read an int but just discard it.

[^\n] means read everything until a newline or eof. push newline back.
%*c means read a byte and discard it.
%*[^\n]%*c reads and discards everything until a newline is met, which
it also discards.

[hdsalbki]

vipps...@gmail. com wrote:

On Jul 13, 2:07 pm, hdsalbki <hdsal...@gmail .comwrote:

vipps...@gmail. com wrote:

<snip>

if(scanf("%c%*[^\n]%*c") < 1) break;

<snip>

Thank you so much vippstar! I was really scratching my head with this
problem and my book said nothing about scanf() leaving the \n in
input. I will do the fixes you suggest but I just can't understand
your scanf() call after the "%c"...what do all those characters do?
can you please explain? thanks again.

See Mr Schmitz correction on my post to get the correct source code.
%* means match conversion but do not "write" to object.
So %*d would read an int but just discard it.
[^\n] means read everything until a newline or eof. push newline back.
%*c means read a byte and discard it.
%*[^\n]%*c reads and discards everything until a newline is met, which
it also discards.

Please correct me if I'm getting this wrong: in your call first
scanf() reads a character and loads it to a then it reads and throws
away everthing to the line end but leaves alone the \n and then reads
the \n and also throws it away. whew! I wish my book explained it like
this. thanks a lot! your code works perfectly. Can you also tell me
why I'm not able to read the function keys and arrow keys? Any way I
can do that?

[hdsalbki]

okay I followed everyone ideas and wrote another version of the
program. Now there is no extra prompt but the code misses every
alternate character I type. Can anyone help? Thanks a lot, never
imagined such a simple thing will be so difficult!

#include <stdio.h>

int main()
{
char a;
while(1)
{
printf("\nPleas e enter a character: ");
fflush(stdout);
if(scanf("%c%*[^\n]%*c",&a) < 1)
{
break;
}
printf("You typed: %c\n",a);
fflush(stdout);
}
return(0);
}

o/p is:

dodo@sapphire:~/src/c/ws$ ./echo_char1

Please enter a character: a
You typed: a

Please enter a character: b
You typed:
Please enter a character: c
You typed: c

Please enter a character: d
You typed:
Please enter a character:

[vippstar]

On Jul 13, 2:58 pm, hdsalbki <hdsal...@gmail .comwrote:

okay I followed everyone ideas and wrote another version of the
program. Now there is no extra prompt but the code misses every
alternate character I type. Can anyone help? Thanks a lot, never
imagined such a simple thing will be so difficult!

#include <stdio.h>

int main()

I told you int main(void), not int main().

{
char a;
while(1)
{
printf("\nPleas e enter a character: ");
fflush(stdout);
if(scanf("%c%*[^\n]%*c",&a) < 1)
{
break;
}
printf("You typed: %c\n",a);
fflush(stdout);

That fflush() is not necessary, as you write a newline to stdout. That
will flush the stream, since it's line buffered. (_IOLBF in setvbuf)

}
return(0);

return is not a function, it's a keyword. the parenthesis are not
needed, just like sizeof. (do not confuse it with sizeof (cast), it's
the cast that requires parenthesis, not sizeof)

>
}

o/p is:

dodo@sapphire:~/src/c/ws$ ./echo_char1

Please enter a character: a
You typed: a

Please enter a character: b
You typed:

Please enter a character: c
You typed: c

Please enter a character: d
You typed:

Please enter a character:

Yeah, it seems that it does not actually read the newline with %*c.
I can't tell you why this happends, perhaps someone else can explain.
Remove the %*c and add a getchar(), and it should work:

if(scanf("%c%^[\n]", &a) < 1) break;
(void)getchar() ;

Note that the cast to (void) is not necessary; I only added it to make
more clear that you don't need to check the return value of getchar.

[hdsalbki]

Thanks to everyone I was able to do this. apart from what vippstar has
sugested I also came with the below code to read the rest of line in
stdin. Is this okay or am I doing something wrong. Thanks for any
comments.

#include <stdio.h>

int main()
{
char a;
while(1)
{
printf("\nPleas e enter a character: ");
fflush(stdout);
scanf("%c",&a);
printf("You entered: %c\n",a);
fflush(stdout);
while(1)
{
scanf("%c",&a);
if(a=='\r' || a=='\n')
{
break;
}
}
}
return 0;
}

[hdsalbki]

hdsalbki wrote:

Thanks to everyone I was able to do this. apart from what vippstar has
sugested I also came with the below code to read the rest of line in
stdin. Is this okay or am I doing something wrong. Thanks for any
comments.

#include <stdio.h>

int main()
{
char a;
while(1)
{
printf("\nPleas e enter a character: ");
fflush(stdout);
scanf("%c",&a);
printf("You entered: %c\n",a);
fflush(stdout);
while(1)
{
scanf("%c",&a);
if(a=='\r' || a=='\n')
{
break;
}
}
}
return 0;
}

Sorry some errors were there. Corrected code follows:

#include <stdio.h>

int main(void)
{
char a;
while(1)
{
printf("\nPleas e enter a character: ");
fflush(stdout);
scanf("%c",&a);
printf("You entered: %c\n",a);
while(1)
{
scanf("%c",&a);
if(a=='\r' || a=='\n')
{
break;
}
}
}
return 0;
}