需要在C fseek的()的 [英] need of fseek() in c
问题描述
code的第1部分: -
Part of Code 1:-
while(1)
{
ch=fgetc(pt);
if(c==EOF)
{
break;
}
if(c==' ')
{
fputc('z',pt);
}
}
code的第2部分: -
Part of Code 2:-
while(1)
{
ch=fgetc(pt);
if(c==EOF)
{
break;
}
if(c==' ')
{
fseek(pt,0,SEEK_CUR);
fputc('z',pt);
fseek(pt,0,SEEK_CUR);
}
}
我想在一个文件中的每个空格
后更换下一个字符。该文件由指针 PT
指出。
I want to replace next character after every space
in a file. That file is pointed by the pointer pt
.
无论是code没有显示出错误并运行良好,但是当我打开外部的 .TXT
文件,首先code什么也没做,而第二个$ C $℃之后空格
成功替换下一个字符。
Both the code shows no error and runs fine, but when I externally opens the .txt
file, first code did nothing whereas the second code replaces the next character after space
successfully.
显然 fseek的(PT,0,SEEK_CUR);
正在差别。
所以我无法理解它在第二code是干什么的?
So I am unable to understand that what it is doing in the second code?
推荐答案
使用的fseek的()
在这里 - 在C标准要求的读取和之间的定位操作上的更新流写操作,或写入和读出之间。这是写和读出之间的定位操作。这不是一个空操作;它流放入一个模式,它允许一个龟etc()
工作正常,可靠,跨平台,所要求的C标准。
The use of fseek()
here - The C standard requires a positioning operation between a read and a write operation on an update stream, or between a write and a read. This is a positioning operation between a write and a read. It is not a no-op; it places the stream into a mode which allows the next fgetc()
to work correctly, reliably, across platforms, as required by the C standard.
编辑:
2 fseek的()
调用必需的,因为第一次充当空操作呼叫的龟etc之间()
和随后的的fputc()
电话。在的fputc()
,第二个充当的fputc之间的不操作()
和随后龟etc()
电话。 (因为一个循环运行)
2 fseek()
calls are required because the first one acts as the "no-op" call between an fgetc()
and a subsequent fputc()
call. After the fputc()
, the second one acts as the "no-op" between the fputc()
and the subsequent fgetc()
call. (since a loop is running)
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