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在头文件<wchar.h>中定义 | ||
---|---|---|
int fwide(FILE * stream,int mode); | (自C95以来) |
如果mode > 0
,试图使stream
广泛导向。如果mode < 0
,试图使stream
字节为导向。如果mode==0
仅查询流的当前方向。
如果流的方向已经确定(通过执行输出或通过先前调用fwide),则此函数不执行任何操作。
流 | - | 指向要修改或查询的CI / O流的指针 |
---|---|---|
模式 | - | 大于零的整数值将流设置为宽度,小于零以将流设置为窄,或者仅将零设置为仅查询 |
如果流在此调用后面向全局,则为大于零的整数,如果流在此调用后面向字节,则小于零;如果流没有定向,则为零。
以下代码设置并重置流的方向。
#include <wchar.h>#include <stdio.h>#include <stdlib.h>void try_read(FILE* fp){ int c = fgetc(fp); if(c == EOF) puts("narrow character read failed"); else printf("narrow character read '%c'\n", c); wint_t wc = fgetwc(fp); if(wc == WEOF) puts("wide character read failed"); else printf("wide character read '%lc'\n", wc);}void show(int n){ if(n == 0) puts("no orientation"); else if (n < 0) puts("narrow orientation"); else puts("wide orientation");}int main(void){ FILE* fp = fopen("main.cpp","r"); if (!fp) { perror("fopen() failed"); return EXIT_FAILURE; } // A newly opened stream has no orientation. show(fwide(fp, 0)); // Establish byte orientation. show(fwide(fp, -1)); try_read(fp); // Only freopen() can reset stream orientation. if (freopen("main.cpp","r",fp) == NULL) { perror("freopen() failed"); return EXIT_FAILURE; } // A reopened stream has no orientation. show(fwide(fp, 0)); // Establish wide orientation. show(fwide(fp, 1)); try_read(fp); fclose(fp);}
可能的输出:
no orientation narrow orientation narrow character read '#'wide character read failed no orientation wide orientation narrow character read failed wide character read '#'
C11标准(ISO / IEC 9899:2011):
7.29.3.5 fwide函数(p:423)
C99标准(ISO / IEC 9899:1999):
7.24.3.5 fwide函数(p:369)