我正在編寫一次讀取輸入一個字符並確定它是十進制,八進制還是十六進制並將其轉換爲十進制輸出的程序。這部分工作,問題是我使用while((ch=getchar()) != EOF)
來通過文本,但while循環永遠不會終止。我聽說EOF等於-1,使用EOF的方法是控制+ z來結束程序,但我希望它是自動的。我一直在使用標準輸入以及爲它提供.txt文本,並且這兩種方式都不會終止程序。我想知道是否有人可以看看我的代碼,看看我哪裏出了問題。C沒有檢測到EOF
(這是很長,我很抱歉,我只是不知道如果這件事情,我的案件中完成與否)
int main (void)
{
int ch, chVal, decVal ;
ch=getchar() ;
while ((ch != EOF))
{
switch (ch)
{
case ' ' :
/* Just read until it’s not a space */
while((ch == SPACE) || (ch== EOL))
ch=getchar();
case '0' :
/* integer, octal or hex possibilities */
ch=getchar() ;
/**** HEX ****/
if ((ch=='x') || (ch=='X'))
{
/* potential hex. So far we have read in 0x. We need to see what's next. */
ch=getchar() ;
if (ch== SPACE)
{
/* all we had was 0x entered */
outputIllegalToken() ;
break ; /* we need to end every pass through the switch with a space char (space, eoln or eof) */
}
decVal=0 ;
while ((('0' <= ch) && (ch <= '9')) || (('a' <= ch) && (ch <= 'f')) || ('A' <= ch) && (ch <= 'F'))
{
chVal = DecToHex(ch) ;
decVal*=16 ;
decVal+=chVal ;
ch=getchar() ;
}
/* ch is no longer a hex val. */
if (ch == SPACE || ch == EOL || ch == EOF)
{
/* All is good. */
outputHex(decVal);
}
else
{
if (ch=='l' || ch=='L')
{
ch=getchar() ;
if ((ch== SPACE) || (ch== EOL) || (ch==EOF))
{
outputLongHex(decVal) ;
}
else
{
outputIllegalToken() ;
while (ch!= SPACE && ch!= EOL && ch!= EOF)
{
getchar();
}
}
}
else
{
outputIllegalToken() ;
ch = getchar() ;
while ((ch!= SPACE) && (ch!= EOL) && (ch!= EOF))
{
ch=getchar();
}
}
}
printf("do we come here? \n");
count++;
break;
/* end of the 0x scenario ch is a space char */
}
/****** 0 *******/
if (ch==' ')
{
/* just a 0 */
outputDecimal(0);
count++;
break ; /* end of 0 alone scenario. ch is a space */
}
/***** 0L ******/
if (ch=='l' || ch=='L') {
/* if there is space after the l, it's ok. otherwise illegal. */
ch=getchar() ;
if ((ch== SPACE) || (ch== EOL) || (ch==EOF))
{
outputLongDecimal(0);
}
else
{
outputIllegalToken() ;
/* read to the next space */
ch=getchar() ;
while ((ch!= SPACE) && (ch!= EOL) & (ch!=EOF))
{
ch=getchar();
}
}
count++;
break ; /* end of 0L scenario. ch is a space char. */
}
/**** Octal ****/
if (('0'<=ch)&&(ch<='7'))
{
/* potentially octal */
chVal=DecToHex(ch) ;
decVal=chVal ;
ch=getchar() ;
while (('0'<=ch)&&(ch<='7'))
{
decVal*=8 ;
decVal+=DecToHex(ch) ;
ch=getchar() ;
}
/* no longer octal ch */
if (ch== SPACE || ch== EOL || ch==EOF)
{
outputOctal(decVal) ;
}
else
{
if (ch=='l' || ch=='L')
{
ch=getchar() ;
if ((ch== SPACE) || (ch== EOL) || (ch==EOF))
{
outputLongOctal(decVal) ;
}
else
{
outputIllegalToken() ;
while (ch!= SPACE && ch!= EOL && ch!=EOF)
{
getchar();
}
}
}
else
{
outputIllegalToken() ;
ch = getchar() ;
while ((ch!= SPACE) && (ch!= EOL) && (ch!=EOF))
{
ch=getchar();
}
}
count++;
break;/* end octal scenario ch is a space character. */
}
count++;
break ;
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
/* potential decimal input */
chVal=DecToHex(ch) ; /* convert the character to a number */
decVal=chVal ; /* keep track of the overall number */
ch=getchar() ;
while (('0'<=ch) && (ch<='9'))
{
chVal=DecToHex(ch) ;
decVal*=10 ;
decVal+=chVal ;
ch=getchar() ;
}
/* integers have ended. spaces or l is acceptable. everything else is illegal */
if ((ch== SPACE) || (ch== EOL) || (ch==EOF))
{
outputDecimal(decVal) ;
}
else if ((ch=='l') || (ch=='L'))
{
/* next char needs to be space in order to be a valid long integer */
ch==getchar() ;
if ((ch== SPACE) || (ch== EOL) || (ch==EOF))
{
outputLongDecimal(decVal) ;
}
else
{
outputIllegalToken() ;
while ((ch!= SPACE) && (ch!= EOL) && (ch!=EOF))
{
ch=getchar();
}
}
}
count++;
break;
}
}
}
return 0;
}
我不認爲你需要三個'while'循環。只需在空間的case語句中放一個do-nothing,讓外層的'while'循環發揮它的魔力。 –
我猜你正在讀某個地方的EOF,然後是另一個'getchar()'函數,它將會吃掉EOF字符。要麼重新構造您的程序,要麼在其他'getchar'調用下添加EOF檢查。 –
羅伯特你很對。我擺脫了那個while循環。 布爾戈斯如果我使用putchar()來查看外部while循環中的字符循環是什麼,它正在給我一個換行符。我不知道這意味着什麼,但是當我試圖改變while語句以包含(ch!='\ n')時,它也沒有幫助。 – Josephine