How this function works?
Hello guys, I wanted to understand how this function works. I have used it anyway without [roperly understanding its mechanism to remove a newline(\n) from the stream and get only one Character.
Code:char getch(void) { char ch; ch = getchar(); while(getchar()!='\n') ; return(ch); }
Please explain :
1) How this works? When is the original input taken?
2) Why is the while loop empty?
3) Do functions like scanf(),fgets() leave a trailing \n or \0?
Thank You very much.
This qualifies as a homework problem and, under this site's homework policy, you need to demonstrate some genuine effort of your own before expecting help.
How about you offer explanations for those questions. We'll then give you pointers on whether you are right or wrong.
What did you learn about getchar on your previous thread?
http://cboard.cprogramming.com/c-pro...y-sorting.html
If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
If at first you don't succeed, try writing your phone number on the exam paper.
The idea is to read a character, then read more characters and discard them until a newline is read. Then, the character that was first read is returned.Originally Posted by Sankait Laroiya
Note that getchar returns an int, and it might return EOF, so it would be better to write:
Except that you have to consider that the character read by getchar is read as an unsigned char, so if char is signed and if the value read falls outside of the range of signed char, then the result of the conversion from int to char would be implementation defined.Code:char getch(void) { int ch, discard_ch; ch = getchar(); while ((discard_ch = getchar()) != '\n' && discard_ch != EOF) ; return(ch); }
Because there is no work that needs to be done in the loop body; the work is done in the loop condition.
This depends on the function. Read the relevant documentation.
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Its not homework. I am to start my first year in ECE in January 2015. I am learning independently.
Well, that it leaves a trailing newline when we press enter to input a character and It gives a ASCII integer value for every character. Anything else you would like to add?
Suppose I enter 's' the first getchar() reads it along with the newline (\n) then what does the getchar() in while loop does. I am not able to understand it. Is it like: the first getchar()'s newline is read by getchar() in the while loop's condition? and when it encounters a newline in the buffer how does it discard that newline? and in the end function returns 'ch' but ch is still equal to charaacter read+newline, so how it is removed?
Please help me with this. I am stuck
No, the first getchar will read 's' only. A single call to getchar reads a single character, by definition.
ch is only equal to the character read. The newline is discarded in the loop.
Last edited by laserlight; 09-19-2014 at 02:34 AM.
Look up a C++ Reference and learn How To Ask Questions The Smart Way
Can I just point out how rare it is to see laserlight make ANY mistake? :P
Fact - Beethoven wrote his first symphony in C
Okay. So, getchar() reads the character entered and the newline is added to the input stream.
Alos, The while loop checks the stream with getchar() in its condition and if it encounters a newline then \n != \n becomes false so how the newline is discarded, the getchar() just eats it and doesn't care whether the condition is true or false?
Thanks for still answering my questions
Why don't you play with this code for a while
Code:int ch; while ( (ch=getchar()) != EOF ) { printf("Decimal value of char=%d, visual representation=(%c)\n", ch, ch ); }
If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
If at first you don't succeed, try writing your phone number on the exam paper.
It helped bro. Thanks.
So final question: When this becomes false while ( (ch=getchar()) != \n ) the loop breaks out and input buffer becomes completely empty? Like say we had S and \n in buffe, this while loop consumes everything in buffer?
Thanks.
Correct - assuming the '\n' that was read was the last character in the buffer.So final question: When this becomes false while ( (ch=getchar()) != \n ) the loop breaks out and input buffer becomes completely empty? Like say we had S and \n in buffe, this while loop consumes everything in buffer?
