input-buffer


How does input buffering work in C++

岁酱吖の 提交于 2019-12-25 05:30:54
问题 Here is a code snippet. I'm confused as to how the buffering internally works. while(true) { cout << "Enter a character: "; cin.ignore(3, '\n'); ch = cin.get(); // ch is char type cout << "char: ch: " << ch << endl; } Actually cin.ignore(3, '\n') ignores the first three characters and then gets the next immediate character. Till that point its fine. Since, I kept this in a while loop, I was trying to check the behavior of ignore() and get() . For instance, the output for which I checked was

Read two characters consecutively using scanf() in C

前提是你 提交于 2019-12-24 02:33:38
问题 I am trying to input two characters from the user t number of times. Here is my code : int main() { int t; scanf("%d",&t); char a,b; for(i=0; i<t; i++) { printf("enter a: "); scanf("%c",&a); printf("enter b:"); scanf("%c",&b); } return 0; } Strangely the output the very first time is: enter a: enter b: That is, the code doesn't wait for the value of a . 回答1: The problem is that scanf("%d", &t) leaves a newline in the input buffer, which is only consumed by scanf("%c", &a) (and hence a is

getchar not working in switch case (c)

非 Y 不嫁゛ 提交于 2019-12-23 02:18:09
问题 Using a very simple calculator program that prompts a user for an operation to perform, followed by a prompt for two integers on which to perform this operation. The program is supposed to loop after these operations, except in the case where the user enters the character 'q', at which point the program is supposed to quit. #include <stdio.h> int main (void) { char c; int number[2], num1, num2, result; double num1d, num2d, resultd; int done=1; while(done) { printf("\t What sort of operation

Perl IPC::Run3: How to emulate a pty for stdin to child process?

天涯浪子 提交于 2019-12-08 02:43:36
问题 This is a follow up question to IPC::Open3 and determining if child is waiting for input though they admittedly are not related. Take the following sample code: use strict; use warnings; use IPC::Run3; sub foo { my $cmd = shift; my $CH_IN = "foo\n"; run3($cmd, \$CH_IN, my $CH_OUT, my $CH_ERR); return 1; } my @LIST = ( 'command','arg1','arg2','arg3' ); foo \@LIST; For the above code command is another perl script. The child script calls who -m to find who owns stdin from the terminal, which is

getchar not working in switch case (c)

╄→尐↘猪︶ㄣ 提交于 2019-12-07 15:47:27
Using a very simple calculator program that prompts a user for an operation to perform, followed by a prompt for two integers on which to perform this operation. The program is supposed to loop after these operations, except in the case where the user enters the character 'q', at which point the program is supposed to quit. #include <stdio.h> int main (void) { char c; int number[2], num1, num2, result; double num1d, num2d, resultd; int done=1; while(done) { printf("\t What sort of operation would you like to perform? \n \t Type + - * / accordingly. \n"); c = getchar(); printf("\tplease enter a

Can fseek(stdin,1,SEEK_SET) or rewind(stdin) be used to flush the input buffer instead of non-portable fflush(stdin)?

最后都变了- 提交于 2019-12-04 03:17:48
问题 Since I discovered fflush(stdin) is not a portable way to deal with the familiar problem of "newline lurking in the input buffer" ,I have been using the following when I have to use scanf : while((c = getchar()) != '\n' && c != EOF); But today I stumbled across this line which I had noted from cplusplus.com on fflush: fflush()...in files open for update (i.e., open for both reading and writting), the stream shall be flushed after an output operation before performing an input operation. This

Why inside a loop, scanf() with %d does not wait for the user input in case it received an invalid input previously?

无人久伴 提交于 2019-12-02 03:09:51
问题 I am using what scanf() returns when it gets what is expects or when it doesn't. What happens is it gets stuck in the while()` loop. To my knowledge test = scanf("%d", &testNum); returns a 1 if it receives a number and a 0 if not. My code: #include<stdio.h> int main(void) { while (1) { int testNum = 0; int test; printf("enter input"); test = scanf("%d", &testNum); printf("%d", test); if (test == 0) { printf("please enter a number"); testNum = 0; } else { printf("%d", testNum); } } return(0);

How to read terminal's input buffer immediately after keypress

主宰稳场 提交于 2019-11-26 17:19:12
问题 I want to read arrow keypresses in my c program and replace them(immediately in the terminal itself) by some other string. I am trying to implement the bash history functionality as in unix terminals. I wrote this code. int main(int argc, char *argv[]) { char c; char str[1024]; int i = 0; while((c = fgetc(stdin)) != '\n'){ if(((int)c) == 27){ c=fgetc(stdin); c=fgetc(stdin); if (c == 'A') { printf("%c[A%c[2K",27, 27); printf("UP"); } } str[i++] = c; } printf("\n"); return 0; } But, this doesn

工具导航Map