scanfってどうやって使うのですか？

Question

情報オリンピックの過去問の答えを見て思ったのですが、scanf関数ってどんなものですか？

Comments

[can110]

https://teratail.com/help/question-tips#questionTips3

Answer 1

scanf でぐぐればいろいろ解説が出てきます

Comments

[yumetodo]

man scanf
を見るべし

Answer 2

回答になっているかどうかはわかりませんがC++で入力ならこっちのほうがおすすめです。

#include<iostream>
#include<string>
using namespace std;

int main()
{
	string input;
	cout << "文字列を入力してください。"<<endl;
	cin >> input;
	cout << input << "と入力されました。" << endl;
		return 0;
}

ちなみにscanf関数はエラー要素が多く、とても危険な関数です。(scanf使用禁止令を出す会社があるくらい)

Answer 3

こんにちは。

直接的な回答ではないです。すいません。

scanfは大昔からあるC言語の標準ライブラリ関数です。設計が古いため、問題点も多いです。
C++でもscanfを使うことは可能ですが、scanfに比べると設計が新しいstd::istreamを使うことがお薦めです。

Answer 4

/* $Id: scanf.c,v 1.2 2002/08/09 20:56:57 pefo Exp $ */

/*
 * Copyright (c) 2000-2002 Opsycon AB  (www.opsycon.se)
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by Opsycon AB.
 * 4. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 */
#include <stdio.h>
#include <stdarg.h>
#include <string.h>
#include <ctype.h>

#include <pmon.h>

/*
 * ** fscanf --\    sscanf --\
 * **          |                  |
 * **  scanf --+-- vfscanf ----- vsscanf
 * **
 * ** This not been very well tested.. it probably has bugs
 */
static int vfscanf __P((FILE *, const char *, va_list));
static int vsscanf __P((const char *, const char *, va_list));

#define ISSPACE " \t\n\r\f\v"

/*
 *  scanf(fmt,va_alist) 
 */
int 
scanf (const char *fmt, ...)
{
    int             count;
    va_list ap;
    
    va_start (ap, fmt);
    count = vfscanf (stdin, fmt, ap);
    va_end (ap);
    return (count);
}

/*
 *  fscanf(fp,fmt,va_alist)
 */
int 
fscanf (FILE *fp, const char *fmt, ...)
{
    int             count;
    va_list ap;

    va_start (ap, fmt);
    count = vfscanf (fp, fmt, ap);
    va_end (ap);
    return (count);
}

/*
 *  sscanf(buf,fmt,va_alist)
 */
int 
sscanf (const char *buf, const char *fmt, ...)
{
    int             count;
    va_list ap;
    
    va_start (ap, fmt);
    count = vsscanf (buf, fmt, ap);
    va_end (ap);
    return (count);
}

/*
 *  vfscanf(fp,fmt,ap) 
 */
static int
vfscanf (FILE *fp, const char *fmt, va_list ap)
{
    int             count;
    char            buf[MAXLN + 1];

    if (fgets (buf, MAXLN, fp) == 0)
	return (-1);
    count = vsscanf (buf, fmt, ap);
    return (count);
}


/*
 *  vsscanf(buf,fmt,ap)
 */
static int
vsscanf (const char *buf, const char *s, va_list ap)
{
    int             count, noassign, width, base, lflag;
    const char     *tc;
    char           *t, tmp[MAXLN];

    count = noassign = width = lflag = 0;
    while (*s && *buf) {
	while (isspace (*s))
	    s++;
	if (*s == '%') {
	    s++;
	    for (; *s; s++) {
		if (strchr ("dibouxcsefg%", *s))
		    break;
		if (*s == '*')
		    noassign = 1;
		else if (*s == 'l' || *s == 'L')
		    lflag = 1;
		else if (*s >= '1' && *s <= '9') {
		    for (tc = s; isdigit (*s); s++);
		    strncpy (tmp, tc, s - tc);
		    tmp[s - tc] = '\0';
		    atob (&width, tmp, 10);
		    s--;
		}
	    }
	    if (*s == 's') {
		while (isspace (*buf))
		    buf++;
		if (!width)
		    width = strcspn (buf, ISSPACE);
		if (!noassign) {
		    strncpy (t = va_arg (ap, char *), buf, width);
		    t[width] = '\0';
		}
		buf += width;
	    } else if (*s == 'c') {
		if (!width)
		    width = 1;
		if (!noassign) {
		    strncpy (t = va_arg (ap, char *), buf, width);
		    t[width] = '\0';
		}
		buf += width;
	    } else if (strchr ("dobxu", *s)) {
		while (isspace (*buf))
		    buf++;
		if (*s == 'd' || *s == 'u')
		    base = 10;
		else if (*s == 'x')
		    base = 16;
		else if (*s == 'o')
		    base = 8;
		else if (*s == 'b')
		    base = 2;
		if (!width) {
		    if (isspace (*(s + 1)) || *(s + 1) == 0)
			width = strcspn (buf, ISSPACE);
		    else
			width = strchr (buf, *(s + 1)) - buf;
		}
		strncpy (tmp, buf, width);
		tmp[width] = '\0';
		buf += width;
		if (!noassign)
		    atob (va_arg (ap, u_int32_t *), tmp, base);
	    }
	    if (!noassign)
		count++;
	    width = noassign = lflag = 0;
	    s++;
	} else {
	    while (isspace (*buf))
		buf++;
	    if (*s != *buf)
		break;
	    else
		s++, buf++;
	}
    }
    return (count);
}

scanf.c

Answer 5

scanf関数 - 数値の入力

scanf関数