C语言库函数大全及应用实例四

时间:2021-12-16 06:52:18

原文:C语言库函数大全及应用实例四

                                  C语言库函数大全及应用实例四[编程资料]C语言库函数大全及应用实例四

couble fmod (double x, double y);

返回x对y的模,即x/y的余数。

void fnmerge(char *path,const char *drive,const char *dir,const char *name,const char *ext);

由给定的盘区路径文件名扩展名等组成部分建立path。

如果drive给出X:,dir给出\DIR\SUBDIR\,name给出NAME,和.ext给出.EXT,根据给定的组成部分,可建立一个完整的盘区路径文件名path为:

X:\DIR\CUBDIR\NAME.EXT

int fnsplit(const char *path,char *drive,char *cir,char *name,char *ext);

可把由path给出的盘区路径文件名扩展名分解成为各自的组成部分.返回一整型数.

FILE*fopen (const char *filemane,const char *mode);

打开文件filemane返回相联系的流;出错返回NULL。

mode字符串的可取值有:r,打开用于读;w,打开用于写;a,打开用于在原有内容之后写;r+,打开已存在的文件用于更新(读和写);w+创建新文件用于更新;a+,打开用于在原有内容之后更新,若文件不存在就创建。

unsigned FP_OFF(void far *farptr);

返回远指针farptr的地址偏移量。

int fprintf(FILE *stream,const char *format[,argument,...]);

照原样抄写格式串format的内容到流stream中,每遇到一个%,就按规定的格式,依次输出一个表达式argument的值到流stream中,返回写的字符个数。出错时返回EOF。

FILE *stream;

void main( void )

{

long l;

float fp;

char s[81];

char c;

stream = fopen( "fscanf.txt", "w+" );

if( stream == NULL )

printf( "The file fscanf.out was not opened\n" );

else {fprintf( stream, "%s %ld %f%c", "a-string",65000, 3.14159, 'x' );

/* Set pointer to beginning of file: */

fseek( stream, 0L, SEEK_SET );

/* Read data back from file: */

fscanf( stream, "%s", s );

fscanf( stream, "%ld", &l );

fscanf( stream, "%f",

fscanf( stream, "%c", &c );/* Output data read: */

printf( "%s\n", s );

printf( "%ld\n", l );

printf( "%f\n", fp );

printf( "%c\n", c );

fclose( stream ); }

}

int fputc(int c,FILE *stream);

写一个字符到流中。

成功时返回所写的字符,失败或出错时返回EOF。

int fputchar(int c);

送一个字符到屏幕。

等价于fputc(c,stdout);成功时返回所写的字符,失败或出错时返回EOF。

int fputs(const char *s,FILE *stream);

把s所指的以空字符终结的字符串送入流中,不加换行符'\n',不拷贝串结束符'\0'。

成功时返回最后的字符,出错时返回EOF。

size_t fread(void *ptr,size_t size,size_t n,FILE *stream);

从所给的输入流stream中读取的n项数据,每一项数据长度为size字节,到由ptr所指的块中。

成功时返回所读的数据项数(不是字节数);遇到文件结束或出错时可能返回0。

void free(void *block);

释放先前分配的首地址为block的内存块。

int freemem(unsigned segx);

释放先前由allocmem分配的段地址为segx的内存块。

FILE *freopen(const char *filename,const char *mode,FILE *stream);

用filename所指定的文件代替打开的流stream所指定的文件。返回stream,出错时返回NULL。

double frexp(double x int *exponent);

将x分解成尾数合指数。

将给出的双精度数x分解成为在0.5和1之间尾数m和整形的指数n,使原来的x=m*(2的n次方),将整形指数n存入exponent所指的地址中,返回尾数m。

int fscan(FILE *stream,char *format,address,...);

fscanf扫描输入字段,从流stream读入,每读入一个字段,就依次按照由format所指的格式串中取一个从%开始的格式进行格式化之后存入对应的一个地址address中。
返回成功地扫描,转换和存贮输入字段的个数,遇文件结束返回EOF。

FILE *stream;

void main( void )

{

long l;

float fp;

char s[81];

char c;

stream = fopen( "fscanf.txt", "w+" );

if( stream == NULL )

printf( "The file fscanf.out was not opened\n" );

else {fprintf( stream, "%s %ld %f%c", "a-string",65000, 3.14159, 'x' );

/* Set pointer to beginning of file: */

fseek( stream, 0L, SEEK_SET );

/* Read data back from file: */

fscanf( stream, "%s", s );

fscanf( stream, "%ld", &l );

fscanf( stream, "%f",

fscanf( stream, "%c", &c );/* Output data read: */

printf( "%s\n", s );

printf( "%ld\n", l );

printf( "%f\n", fp );

printf( "%c\n", c );

fclose( stream ); }

}

int fseek(FILE *stream,long offset,int whence);

在流上重新定位文件结构的位置。fseek设置与流stream相联系的文件指针到新的位置,新位置与whence给定的文件位置的距离为offset字节。
whence的取值必须是0,1或2中的一个,分别代表在stdio.h中定义的三个符号常量:

0是SEEK_SET,是文件开始位置;

1是SEEK_CUR,是当前的指针位置;

2时SEEK_END,是文件末尾。

调用了fseek之后,在更新的文件位置上,下一个操作可以是输入;也可以是输出。成功地移动了指针时,fseek返回0;出错或失败时返回非0值。

例:

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FILE *stream;

void main( void )

{

long l;

float fp;

char s[81];

char c;

stream = fopen( "fscanf.txt", "w+" );

if( stream == NULL )

printf( "The file fscanf.out was not opened\n" );

else {fprintf( stream, "%s %ld %f%c", "a-string",65000, 3.14159, 'x' );

/* Set pointer to beginning of file: */

fseek( stream, 0L, SEEK_SET );

/* Read data back from file: */

fscanf( stream, "%s", s );

fscanf( stream, "%ld", &l );

fscanf( stream, "%f",

fscanf( stream, "%c", &c );/* Output data read: */

printf( "%s\n", s );

printf( "%ld\n", l );

printf( "%f\n", fp );

printf( "%c\n", c );

fclose( stream ); }

}

int fsetpos(FILE *stream,const fpos_t *pos);

fsetpos把与stream相联系的文件指针置于新的位置。这个新的位置是先前对此流调用fgetpos所得的值。
fsetpos清除stream所指文件的文件结束标志,并消除对该文件的所有ungetc操作。在调用fsetpos之后,文件的下一操作可以是输入或输出。

调用fsetpos成功时返回0;若失败,返回非0值。

int fstat(int handle,struct stat *statbuf);

把与handle相联系的打开文件或目录的信息存入到statbuf所指的定义在sys\stat.h中的stat结构中。成功时返回0;出错时返回-1。

long int ftell(FILE *stream);

返回流stream中当前文件指针位置。偏移量是文件开始算起的字节数。出错时返回-1L,是长整数的-1值。

void ftime(struct timeb *buf);

把当前时间存入到在sys\timeb.h中定义的timeb结构中。

size_t fwrite(const void *ptr,size_t size,size_t n,FILE *stream);

fwrite从指针ptr开始把n个数据项添加到给定输出流stream,每个数据项的长度为size个字节。

成功是返回确切的数据项数(不是字节数);出错时返回短(short)计数值。可能是0。

函数名: gcvt
功 能: 把浮点数转换成字符串
用 法: char *gcvt(double value, int ndigit, char *buf);
程序例:

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int main(void)
{
char str[25];
double num;
int sig = 5; /* significant digits */

/* a regular number */
num = 9.876;
gcvt(num, sig, str);
printf("string = %s\n", str);

/* a negative number */
num = -123.4567;
gcvt(num, sig, str);
printf("string = %s\n", str);

/* scientific notation */
num = 0.678e5;
gcvt(num, sig, str);
printf("string = %s\n", str);

return(0);
}

函数名: geninterrupt
功 能: 产生一个软中断
用 法: void geninterrupt(int intr_num);
程序例:

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/* function prototype */
void writechar(char ch);

int main(void)
{
clrscr();
gotoxy(80,25);
writechar('*');
getch();
return 0;
}

/*
outputs a character at the current cursor
position using the video BIOS to avoid the
scrolling of the screen when writing to
location (80,25).
*/

void writechar(char ch)
{
struct text_info ti;
/* grab current text settings */
gettextinfo(&ti);
/* interrupt 0x10 sub-function 9 */
_AH = 9;
/* character to be output */
_AL = ch;
_BH = 0; /* video page */
_BL = ti.attribute; /* video attribute */
_CX = 1; /* repetition factor */
geninterrupt(0x10); /* output the char */
}

函数名: getarccoords
功 能: 取得最后一次调用arc的坐标
用 法: void far getarccoords(struct arccoordstype far *arccoords);
程序例:

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int main(void)
{
/* request auto detection */
int gdriver = DETECT, gmode, errorcode;
struct arccoordstype arcinfo;
int midx, midy;
int stangle = 45, endangle = 270;
char sstr[80], estr[80];

/* initialize graphics and local variables */
initgraph(&gdriver, &gmode, "");

/* read result of initialization */
errorcode = graphresult();
/* an error occurred */
if (errorcode != grOk)
{
printf("Graphics error: %s\n",
grapherrormsg(errorcode));
printf("Press any key to halt:");
getch();
/* terminate with an error code */
exit(1);
}

midx = getmaxx() / 2;
midy = getmaxy() / 2;

/* draw arc and get coordinates */
setcolor(getmaxcolor());
arc(midx, midy, stangle, endangle, 100);
getarccoords(&arcinfo);

/* convert arc information into strings */
sprintf(sstr, "*- (%d, %d)",
arcinfo.xstart, arcinfo.ystart);
sprintf(estr, "*- (%d, %d)",
arcinfo.xend, arcinfo.yend);

/* output the arc information */
outtextxy(arcinfo.xstart,
arcinfo.ystart, sstr);
outtextxy(arcinfo.xend,
arcinfo.yend, estr);

/* clean up */
getch();
closegraph();
return 0;
}

函数名: getaspectratio
功 能: 返回当前图形模式的纵横比
用 法: void far getaspectratio(int far *xasp, int far *yasp);
程序例:

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int main(void)
{
/* request auto detection */
int gdriver = DETECT, gmode, errorcode;
int xasp, yasp, midx, midy;

/* initialize graphics and local variables */
initgraph(&gdriver, &gmode, "");

/* read result of initialization */
errorcode = graphresult();
/* an error occurred */
if (errorcode != grOk)
{
printf("Graphics error: %s\n",
grapherrormsg(errorcode));
printf("Press any key to halt:");
getch();
/* terminate with an error code */
exit(1);
}

midx = getmaxx() / 2;
midy = getmaxy() / 2;
setcolor(getmaxcolor());

/* get current aspect ratio settings */
getaspectratio(&xasp, &yasp);

/* draw normal circle */
circle(midx, midy, 100);
getch();

/* draw wide circle */
cleardevice();
setaspectratio(xasp/2, yasp);
circle(midx, midy, 100);
getch();

/* draw narrow circle */
cleardevice();
setaspectratio(xasp, yasp/2);
circle(midx, midy, 100);

/* clean up */
getch();
closegraph();
return 0;
}

函数名: getbkcolor
功 能: 返回当前背景颜色
用 法: int far getbkcolor(void);
程序例:

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int main(void)
{
/* request auto detection */
int gdriver = DETECT, gmode, errorcode;
int bkcolor, midx, midy;
char bkname[35];

/* initialize graphics and local variables */
initgraph(&gdriver, &gmode, "");

/* read result of initialization */
errorcode = graphresult();
/* an error occurred */
if (errorcode != grOk)
{
printf("Graphics error: %s\n",
grapherrormsg(errorcode));
printf("Press any key to halt:");
getch();
/* terminate with an error code */
exit(1);
}

midx = getmaxx() / 2;
midy = getmaxy() / 2;
setcolor(getmaxcolor());

/* for centering text on the display */
settextjustify(CENTER_TEXT, CENTER_TEXT);

/* get the current background color */
bkcolor = getbkcolor();

/* convert color value into a string */
itoa(bkcolor, bkname, 10);
strcat(bkname,
" is the current background color.");

/* display a message */
outtextxy(midx, midy, bkname);

/* clean up */
getch();
closegraph();
return 0;
}

函数名: getc
功 能: 从流中取字符
用 法: int getc(FILE *stream);
程序例:

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int main(void)
{
char ch;

printf("Input a character:");
/* read a character from the
standard input stream */
ch = getc(stdin);
printf("The character input was: '%c'\n",
ch);
return 0;
}

函数名: getcbrk
功 能: 获取Control_break设置
用 法: int getcbrk(void);
程序例:

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int main(void)
{
if (getcbrk())
printf("Cntrl-brk flag is on\n");
else
printf("Cntrl-brk flag is off\n");

return 0;
}

函数名: getch
功 能: 从控制台无回显地取一个字符
用 法: int getch(void);
程序例:

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int main(void)
{
char ch;

printf("Input a character:");
ch = getche();
printf("\nYou input a '%c'\n", ch);
return 0;
}

函数名: getchar
功 能: 从stdin流中读字符
用 法: int getchar(void);
程序例:

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int main(void)
{
int c;

/* Note that getchar reads from stdin and
is line buffered; this means it will
not return until you press ENTER. */

while ((c = getchar()) != '\n')
printf("%c", c);

return 0;
}

函数名: getche
功 能: 从控制台取字符(带回显)
用 法: int getche(void);
程序例:

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int main(void)
{
char ch;

printf("Input a character:");
ch = getche();
printf("\nYou input a '%c'\n", ch);
return 0;
}

函数名: getcolor
功 能: 返回当前画线颜色
用 法: int far getcolor(void);
程序例:

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int main(void)
{
/* request auto detection */
int gdriver = DETECT, gmode, errorcode;
int color, midx, midy;
char colname[35];

/* initialize graphics and local variables */
initgraph(&gdriver, &gmode, "");

/* read result of initialization */
errorcode = graphresult();
/* an error occurred */
if (errorcode != grOk)
{
printf("Graphics error: %s\n",
grapherrormsg(errorcode));
printf("Press any key to halt:");
getch();
/* terminate with an error code */
exit(1);
}

midx = getmaxx() / 2;
midy = getmaxy() / 2;
setcolor(getmaxcolor());

/* for centering text on the display */
settextjustify(CENTER_TEXT, CENTER_TEXT);

/* get the current drawing color */
color = getcolor();

/* convert color value into a string */
itoa(color, colname, 10);
strcat(colname,
" is the current drawing color.");

/* display a message */
outtextxy(midx, midy, colname);

/* clean up */
getch();
closegraph();
return 0;
}