cconsolescanfnewlineconemu

scanf() no carriage return after printf()


I have the following code that reads 4 numbers from user input:

#include <stdio.h>
#include <stdlib.h>

#define MAX_NUMS 4

int main()
{
    int nums[MAX_NUMS];

    int i;
    int num;

    for (i = 0; i < MAX_NUMS; i++)
    {
        do
        {
            printf("Enter a value between 1 and 9: ");
            scanf("%i",&num);
        }
        while(num > 9 || num < 1);

        nums[i] = num;
    }

    return 0;
}

And when I run it, I get the following output:

user@USER:/cygdrive/d
$ ./test.exe
Enter a value between 1 and 9: 1
                                Enter a value between 1 and 9: 2
                                                                Enter a value between 1 and 9: 3
                                                                                                Enter a value between 1 and 9: 4
                                                                                                                                user@USER:/cygdrive/d
$

Why there is no carriage return when I press enter after entering the numbers? Am I missing something?

I am on cygwin:

user@USER:/cygdrive/d
$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-cygwin/9.3.0/lto-wrapper.exe
Target: x86_64-pc-cygwin
Configured with: /cygdrive/i/szsz/tmpp/gcc/gcc-9.3.0-2.x86_64/src/gcc-9.3.0/configure --srcdir=/cygdrive/i/szsz/tmpp/gcc/gcc-9.3.0-2.x86_64/src/gcc-9.3.0 --prefix=/usr --exec-prefix=/usr --localstatedir=/var --sysconfdir=/etc --docdir=/usr/share/doc/gcc --htmldir=/usr/share/doc/gcc/html -C --build=x86_64-pc-cygwin --host=x86_64-pc-cygwin --target=x86_64-pc-cygwin --without-libiconv-prefix --without-libintl-prefix --libexecdir=/usr/lib --enable-shared --enable-shared-libgcc --enable-static --enable-version-specific-runtime-libs --enable-bootstrap --enable-__cxa_atexit --with-dwarf2 --with-tune=generic --enable-languages=c,c++,fortran,lto,objc,obj-c++ --enable-graphite --enable-threads=posix --enable-libatomic --enable-libgomp --enable-libquadmath --enable-libquadmath-support --disable-libssp --enable-libada --disable-symvers --with-gnu-ld --with-gnu-as --with-cloog-include=/usr/include/cloog-isl --without-libiconv-prefix --without-libintl-prefix --with-system-zlib --enable-linker-build-id --with-default-libstdcxx-abi=gcc4-compatible --enable-libstdcxx-filesystem-ts
Thread model: posix
gcc version 9.3.0 (GCC)
user@USER:/cygdrive/d
$ uname -a
CYGWIN_NT-10.0 STEPAN 3.1.5(0.340/5/3) 2020-06-01 08:59 x86_64 Cygwin
user@USER:/cygdrive/d
$ echo $TERM
xterm-256color

Solution

  • It seems that in your specific environment the Enter key you press to confirm you input is interpreted as a raw '\n'. The original meaning of this character, in fact, is line feed, that means "change line without performing a carriage return" ('\r').

    In most terminals the enter key sums the effects of \r and \n, and this doesn't happen in your case.

    To work it around try inserting manually a '\r' after the input insertion:

    do
    {
        printf("Enter a value between 1 and 9: ");
        scanf("%i",&num);
        printf("\r");
    }
    while(num > 9 || num < 1);