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arithmeticconjconjfconjlcopysigncopysignfcopysignlcoscosfcoshcoshfcoshlcoslcpowcpowfcpowlcprojcprojfcprojlcrealcrealfcreallcsincsinfcsinhcsinhfcsinhlcsinlcsqrtcsqrtfcsqrtlctanctanfctanhctanhfctanhlctanldivdouble_terferfcerfcferfclerfferflexpexp2exp2fexp2lexpfexplexpm1expm1fexpm1lfabsfabsffabslfdimfeclearexceptfegetenvfegetexceptflagfegetroundfeholdexceptferaiseexceptfesetenvfesetexceptflagfesetroundfetestexceptfeupdateenvFE_ALL_EXCEPTFE_DFL_ENVFE_DIVBYZEROFE_DOWNWARDFE_INEXACTFE_INVALIDFE_OVERFLOWFE_TONEARESTFE_TOWARDZEROFE_UNDERFLOWFE_UPWARDFloating-point 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stringsNull-terminated wide stringsstrcatstrcat_sstrchrstrcmpstrcollstrcpystrcpy_sstrcspnstrerrorstrerrorlen_sstrerror_sStrings librarystrlenstrncatThread supportcall_oncecnd_broadcastcnd_destroycnd_initcnd_signalcnd_timedwaitcnd_waitmtx_destroymtx_initmtx_lockmtx_plainmtx_recursivemtx_timedmtx_timedlockmtx_trylockmtx_unlockonce_flagONCE_FLAG_INITthrd_busythrd_createthrd_currentthrd_detachthrd_equalthrd_errorthrd_exitthrd_jointhrd_nomemthrd_sleepthrd_successthrd_timedoutthrd_yieldThread support librarythread_localtss_createtss_deleteTSS_DTOR_ITERATIONStss_gettss_setType supportBoolean type support libraryFixed width integer typesFLT_EVAL_METHODFLT_ROUNDSmax_align_tNULLNumeric limitsoffsetofptrdiff_tsize_tType supportVariadic functionsVariadic functionsva_argva_copyva_endva_listva_start

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在头文件<stdio.h>中定义



size_t fwrite（const void * buffer，size_t size，size_t count，FILE * stream）;


（直到C99）

size_t fwrite（const void * restrict buffer，size_t size，size_t count，FILE * restrict stream）;


（自C99以来）

count将给定数组中的对象写入buffer输出流stream。这些目的通过reinterepreting每个对象作为数组写为如果unsigned char与呼叫fputc size时间为每个对象写入那些unsigned chars转换stream，为了。流的文件位置指示符按写入的字符数进行提前。

参数

缓冲

-

指向数组中要写入的第一个对象的指针

尺寸

-

每个对象的大小

计数

-

要写入的对象的数量

流

-

指向输出流的指针

返回值

成功写入的对象数量可能少于count发生错误时的数量。

如果size或者count为零，则fwrite返回零且不执行其他操作。

例

#include <stdio.h>#include <stdlib.h>#include <assert.h>enum { SIZE = 5 };int main(void){
    double a[SIZE] = {1, 2, 3, 4, 5};
    FILE *f1 = fopen("file.bin", "wb");    assert(f1);
    int r1 = fwrite(a, sizeof a[0], SIZE, f1);    printf("wrote %d elements out of %d requested\n", r1,  SIZE);    fclose(f1);
 
    double b[SIZE];
    FILE *f2 = fopen("file.bin", "rb");
    int r2 = fread(b, sizeof b[0], SIZE, f2);    fclose(f2);    printf("read back: ");    for(int i = 0; i < r2; i++)        printf("%f ", b[i]);}

输出：

wrote 5 elements out of 5 requested
read back: 1.000000 2.000000 3.000000 4.000000 5.000000

参考

  • C11标准（ISO / IEC 9899：2011）：

    • 7.21.8.2 fwrite函数（p：335-336）

  • C99标准（ISO / IEC 9899：1999）：

    • 7.19.8.2 fwrite函数（p：301-302）

  • C89 / C90标准（ISO / IEC 9899：1990）：

    • 4.9.8.2 fwrite函数

printfprintfsprintfsnprintfprintf_sfprintf_ssprintf_ssnprintf_s（C99）（C11）（C11）（C11）（C11）

打印格式化输出到标准输出，文件流或缓冲区（功能）

的fputs

将字符串写入文件流（函数）

FREAD

从文件读取（功能）

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