关于 while(!EOF) 的问题
我从 stdin 读取值，我想继续读取该文件，直到我完全读取它，所以我使用
while(!EOF){ scanf(...) }
但是，代码片段似乎没有做任何事情，
while(!EOF){
scanf("%d %d %d %d", &imageWidth, &imageHeight, &safeRegionStart, &safeRegionWidth);
printf("---imageWidth=%d imageHeight=%d safeRegionStart=%d safeRegionWidth=%d---\n", imageWidth, imageHeight, safeRegionStart, safeRegionWidth);
totalP = imageWidth * imageHeight ;
totalSafeP = imageHeight * safeRegionWidth;
printf("---total # of pixels: %d Total # of safe Pixels: %d---\n\n", totalP, totalSafeP);
i=1;
while(i!=totalP)
{
i++;
scanf("%d", &pixel);
printf("\nValue of pixel %d", pixel);
}//End for scanning all pixels*/
}//while loop
编辑：我修复了它
while(scanf("%d %d %d %d", &imageWidth, &imageHeight, &safeRegionStart, &safeRegionWidth)==4&&!feof(stdin)) { }
!feof(stdin) 可能没有必要。
Im reading in values from stdin and I want to keep reading the file until I have completed reading it all the way, so I am using
while(!EOF){ scanf(...) }
However, the code fragment doesn't seem to do anything,
while(!EOF){
scanf("%d %d %d %d", &imageWidth, &imageHeight, &safeRegionStart, &safeRegionWidth);
printf("---imageWidth=%d imageHeight=%d safeRegionStart=%d safeRegionWidth=%d---\n", imageWidth, imageHeight, safeRegionStart, safeRegionWidth);
totalP = imageWidth * imageHeight ;
totalSafeP = imageHeight * safeRegionWidth;
printf("---total # of pixels: %d Total # of safe Pixels: %d---\n\n", totalP, totalSafeP);
i=1;
while(i!=totalP)
{
i++;
scanf("%d", &pixel);
printf("\nValue of pixel %d", pixel);
}//End for scanning all pixels*/
}//while loop
EDIT: I fixed it
while(scanf("%d %d %d %d", &imageWidth, &imageHeight, &safeRegionStart, &safeRegionWidth)==4&&!feof(stdin)) { }
!feof(stdin) probably isn't necessary.
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评论（4）
EOF只是一个整数常量。在大多数系统上它是-1。!-1是false并且while(false)不会做任何事情。您想要的是检查
scanf的返回值。scanf返回成功读取的项目数，并最终返回EOF。EOFis only an integer constant. On most systems it is-1.!-1isfalseandwhile(false)won't do anything.What you want is to check the return values of
scanf.scanfreturns the number of successfully read items and eventuallyEOF.嗯，这很容易回答：
EOF 是一个常量
#define，例如#define EOF -1。因此，您的
while(!EOF)条件将始终为 false，并且循环不会执行。您需要根据 EOF 检查scanf的返回值。你需要类似的东西：
Well, this is easy to answer:
EOF is a constant
#define, e.g.#define EOF -1.So your
while(!EOF)condition will always be false and the loop won't execute. You need to check the return value ofscanfagainst EOF.You need something like:
您必须使用变量来保存可能为 EOF 的 char 值。类似 ..
否则 !EOF 总是错误的。
You have to use a variable to hold a char value that can be potentially
EOF. Something like ..Otherwise !EOF is always false.
永远不会进入循环。
EOF是一个常量值，即-1（请检查stdio.h来了解此定义）。因此!EOF是0，这是 false，因此永远不会被输入。要检查文件是否已结束，可以使用：
if (feof (file_ptr)) break;The loop will never be entered.
EOFis a constant value which is-1(checkstdio.hfor this definition). So!EOFis0which is false, so it will never be entered.To check that if the file has ended or not you can use:
if (feof (file_ptr)) break;