Linux C语言常用函数 05

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C和C++面试笔试题

函数名: poke

功能: 存值到一个给定存储单元

用法: void poke(int segment, int offset, int value);

程序例:

#include ;

int main(void)

{

clrscr();

cprintf("Make sure the scroll lock key is off and press any key\r\n");

getch();

poke(0x0000,0x0417,16);

cprintf("The scroll lock is now on\r\n");

return 0;

}

函数名: pokeb

功能: 存值到一个给定存储单元

用法: void pokeb(int segment, int offset, char value);

程序例:

#include ;

int main(void)

{

clrscr();

cprintf("Make sure the scroll lock key is off and press any key\r\n");

getch();

pokeb(0x0000,0x0417,16);

cprintf("The scroll lock is now on\r\n");

return 0;

}

函数名: poly

功能: 根据参数产生一个多项式

用法: double poly(double x, int n, double c[]);

程序例:

#include ;

/* polynomial: x**3 - 2x**2 + 5x - 1 */

int main(void)

{

double array[] = { -1.0, 5.0, -2.0, 1.0 };

double result;

result = poly(2.0, 3, array);

printf("The polynomial: x**3 - 2.0x**2 + 5x - 1 at 2.0 is %lf\n",

result);

return 0;

}

函数名: pow

功能: 指数函数(x的y次方)

用法: double pow(double x, double y);

程序例:

#include ;

int main(void)

{

double x = 2.0, y = 3.0;

printf("%lf raised to %lf is %lf\n", x, y, pow(x, y));

return 0;

}

函数名: pow10

功能: 指数函数(10的p次方)

用法: double pow10(int p);

程序例:

#include ;

int main(void)

{

double p = 3.0;

printf("Ten raised to %lf is %lf\n", p, pow10(p));

return 0;

}

函数名: printf

功能: 产生格式化输出的函数

用法: int printf(char *format...);

程序例:

#include ;

#define I 555

#define R 5.5

int main(void)

{

int i,j,k,l;

char buf[7];

char *prefix = buf;

char tp[20];

printf("prefix 6d 6o 8x 10.2e "

"10.2f\n");

strcpy(prefix,"%");

for (i = 0; i 函数名: putc

功能: 输出一字符到指定流中

用法: int putc(int ch, FILE *stream);

程序例:

#include ;

int main(void)

{

char msg[] = "Hello world\n";

int i = 0;

while (msg)

putc(msg[i++], stdout);

return 0;

}

函数名: putch

功能: 输出字符到控制台

用法: int putch(int ch);

程序例:

#include ;

int main(void)

{

char ch = 0;

printf("Input a string:");

while ((ch != '\r'))

{

ch = getch();

putch(ch);

}

return 0;

}

函数名: putchar

功能: 在stdout上输出字符

用法: int putchar(int ch);

程序例:

#include ;

/* define some box-drawing characters */

#define LEFT_TOP 0xDA

#define RIGHT_TOP 0xBF

#define HORIZ 0xC4

#define VERT 0xB3

#define LEFT_BOT 0xC0

#define RIGHT_BOT 0xD9

int main(void)

{

char i, j;

/* draw the top of the box */

putchar(LEFT_TOP);

for (i=0; i函数名: putenv

功能: 把字符串加到当前环境中

用法: int putenv(char *envvar);

程序例:

#include ;

int main(void)

{

char *path, *ptr;

int i = 0;

/* get the current path environment */

ptr = getenv("PATH");

/* set up new path */

path = malloc(strlen(ptr)+15);

strcpy(path,"PATH=");

strcat(path,ptr);

strcat(path,";c:\\temp");

/* replace the current path and display current environment */

putenv(path);

while (environ)

printf("%s\n",environ[i++]);

return 0;

}

函数名: putimage

功能: 在屏幕上输出一个位图

用法: void far putimage(int x, int y, void far *bitmap, int op);

程序例:

#include ;

#define ARROW_SIZE 10

void draw_arrow(int x, int y);

int main(void)

{

/* request autodetection */

int gdriver = DETECT, gmode, errorcode;

void *arrow;

int x, y, maxx;

unsigned int size;

/* initialize graphics and local variables */

initgraph(&gdriver, &gmode, "");

/* read result of initialization */

errorcode = graphresult();

if (errorcode != grOk) /* an error occurred */

{

printf("Graphics error: %s\n", grapherrormsg(errorcode));

printf("Press any key to halt:");

getch();

exit(1); /* terminate with an error code */

}

maxx = getmaxx();

x = 0;

y = getmaxy() / 2;

/* draw the image to be grabbed */

draw_arrow(x, y);

/* calculate the size of the image */

size = imagesize(x, y-ARROW_SIZE, x+(4*ARROW_SIZE), y+ARROW_SIZE);

/* allocate memory to hold the image */

arrow = malloc(size);

/* grab the image */

getimage(x, y-ARROW_SIZE, x+(4*ARROW_SIZE), y+ARROW_SIZE, arrow);

/* repeat until a key is pressed */

while (!kbhit())

{

/* erase old image */

putimage(x, y-ARROW_SIZE, arrow, XOR_PUT);

x += ARROW_SIZE;

if (x >;= maxx)

x = 0;

/* plot new image */

putimage(x, y-ARROW_SIZE, arrow, XOR_PUT);

}

/* clean up */

free(arrow);

closegraph();

return 0;

}

void draw_arrow(int x, int y)

{

/* draw an arrow on the screen */

moveto(x, y);

linerel(4*ARROW_SIZE, 0);

linerel(-2*ARROW_SIZE, -1*ARROW_SIZE);

linerel(0, 2*ARROW_SIZE);

linerel(2*ARROW_SIZE, -1*ARROW_SIZE);

}

函数名: putpixel

功能: 在指定位置画一像素

用法: void far putpixel (int x, int y, int pixelcolor);

程序例:

#include ;

#define PIXEL_COUNT 1000

#define DELAY_TIME 100 /* in milliseconds */

int main(void)

{

/* request autodetection */

int gdriver = DETECT, gmode, errorcode;

int i, x, y, color, maxx, maxy, maxcolor, seed;

/* initialize graphics and local variables */

initgraph(&gdriver, &gmode, "");

/* read result of initialization */

errorcode = graphresult();

if (errorcode != grOk) /* an error occurred */

{

printf("Graphics error: %s\n", grapherrormsg(errorcode));

printf("Press any key to halt:");

getch();

exit(1); /* terminate with an error code */

}

maxx = getmaxx() + 1;

maxy = getmaxy() + 1;

maxcolor = getmaxcolor() + 1;

while (!kbhit())

{

/* seed the random number generator */

seed = random(32767);

srand(seed);

for (i=0; i函数名: puts

功能: 送一字符串到流中

用法: int puts(char *string);

程序例:

#include ;

int main(void)

{

char string[] = "This is an example output string\n";

puts(string);

return 0;

}

函数名: puttext

功能: 将文本从存储区拷贝到屏幕

用法: int puttext(int left, int top, int right, int bottom, void *source);

程序例:

#include ;

int main(void)

{

char buffer[512];

/* put some text to the console */

clrscr();

gotoxy(20, 12);

cprintf("This is a test. Press any key to continue ...");

getch();

/* grab screen contents */

gettext(20, 12, 36, 21,buffer);

clrscr();

/* put selected characters back to the screen */

gotoxy(20, 12);

puttext(20, 12, 36, 21, buffer);

getch();

return 0;

}

函数名: putw

功能: 把一字符或字送到流中

用法: int putw(int w, FILE *stream);

程序例:

#include ;

#define FNAME "test.$$$"

int main(void)

{

FILE *fp;

int word;

/* place the word in a file */

fp = fopen(FNAME, "wb");

if (fp == NULL)

{

printf("Error opening file %s\n", FNAME);

exit(1);

}

word = 94;

putw(word,fp);

if (ferror(fp))

printf("Error writing to file\n");

else

printf("Successful write\n");

fclose(fp);

/* reopen the file */

fp = fopen(FNAME, "rb");

if (fp == NULL)

{

printf("Error opening file %s\n", FNAME);

exit(1);

}

/* extract the word */

word = getw(fp);

if (ferror(fp))

printf("Error reading file\n");

else

printf("Successful read: word = %d\n", word);

/* clean up */

fclose(fp);

unlink(FNAME);

return 0;

}

CODE:

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函数名: qsort

功能: 使用快速排序例程进行排序

用法: void qsort(void *base, int nelem, int width, int (*fcmp)());

程序例:

#include ;

int sort_function( const void *a, const void *b);

char list[5][4] = { "cat", "car", "cab", "cap", "can" };

int main(void)

{

int x;

qsort((void *)list, 5, sizeof(list[0]), sort_function);

for (x = 0; x 函数名: raise

功能: 向正在执行的程序发送一个信号

用法: int raise(int sig);

程序例:

#include ;

int main(void)

{

int a, b;

a = 10;

b = 0;

if (b == 0)

/* preempt divide by zero error */

raise(SIGFPE);

a = a / b;

return 0;

}

函数名: rand

功能: 随机数发生器

用法: void rand(void);

程序例:

#include ;

int main(void)

{

int i;

printf("Ten random numbers from 0 to 99\n\n");

for(i=0; i函数名: randbrd

功能: 随机块读

用法: int randbrd(struct fcb *fcbptr, int reccnt);

程序例:

#include ;

int main(void)

{

char far *save_dta;

char line[80], buffer[256];

struct fcb blk;

int i, result;

/* get user input file name for dta */

printf("Enter drive and file name (no path - i.e. a:file.dat)\n");

gets(line);

/* put file name in fcb */

if (!parsfnm(line, &blk, 1))

{

printf("Error in call to parsfnm\n");

exit(1);

}

printf("Drive #%d File: %s\n\n", blk.fcb_drive, blk.fcb_name);

/* open file with DOS FCB open file */

bdosptr(0x0F, &blk, 0);

/* save old dta, and set new one */

save_dta = getdta();

setdta(buffer);

/* set up info for the new dta */

blk.fcb_recsize = 128;

blk.fcb_random = 0L;

result = randbrd(&blk, 1);

/* check results from randbrd */

if (!result)

printf("Read OK\n\n");

else

{

perror("Error during read");

exit(1);

}

/* read in data from the new dta */

printf("The first 128 characters are:\n");

for (i=0; i函数名: randbwr

功能: 随机块写

用法: int randbwr(struct fcp *fcbptr, int reccnt);

程序例:

#include ;

int main(void)

{

char far *save_dta;

char line[80];

char buffer[256] = "RANDBWR test!";

struct fcb blk;

int result;

/* get new file name from user */

printf("Enter a file name to create (no path - ie. a:file.dat\n");

gets(line);

/* parse the new file name to the dta */

parsfnm(line,&blk,1);

printf("Drive #%d File: %s\n", blk.fcb_drive, blk.fcb_name);

/* request DOS services to create file */

if (bdosptr(0x16, &blk, 0) == -1)

{

perror("Error creating file");

exit(1);

}

/* save old dta and set new dta */

save_dta = getdta();

setdta(buffer);

/* write new records */

blk.fcb_recsize = 256;

blk.fcb_random = 0L;

result = randbwr(&blk, 1);

if (!result)

printf("Write OK\n");

else

{

perror("Disk error");

exit(1);

}

/* request DOS services to close the file */

if (bdosptr(0x10, &blk, 0) == -1)

{

perror("Error closing file");

exit(1);

}

/* reset the old dta */

setdta(save_dta);

return 0;

}

函数名: random

功能: 随机数发生器

用法: int random(int num);

程序例:

#include ;

/* prints a random number in the range 0 to 99 */

int main(void)

{

randomize();

printf("Random number in the 0-99 range: %d\n", random (100));

return 0;

}

函数名: randomize

功能: 初始化随机数发生器

用法: void randomize(void);

程序例:

#include ;

int main(void)

{

int i;

randomize();

printf("Ten random numbers from 0 to 99\n\n");

for(i=0; i函数名: read

功能: 从文件中读

用法: int read(int handle, void *buf, int nbyte);

程序例:

#include ;

int main(void)

{

void *buf;

int handle, bytes;

buf = malloc(10);

Looks for a file in the current directory named TEST.$$$ and attempts

to read 10 bytes from it. To use this example you should create the

file TEST.$$$

if ((handle =

open("TEST.$$$", O_RDONLY | O_BINARY, S_IWRITE | S_IREAD)) == -1)

{

printf("Error Opening File\n");

exit(1);

}

if ((bytes = read(handle, buf, 10)) == -1) {

printf("Read Failed.\n");

exit(1);

}

else {

printf("Read: %d bytes read.\n", bytes);

}

return 0;

}

函数名: realloc

功能: 重新分配主存

用法: void *realloc(void *ptr, unsigned newsize);

程序例:

#include ;

int main(void)

{

char *str;

/* allocate memory for string */

str = malloc(10);

/* copy "Hello" into string */

strcpy(str, "Hello");

printf("String is %s\n Address is %p\n", str, str);

str = realloc(str, 20);

printf("String is %s\n New address is %p\n", str, str);

/* free memory */

free(str);

return 0;

}

函数名: rectangle

功能: 画一个矩形

用法: void far rectangle(int left, int top, int right, int bottom);

程序例:

#include ;

int main(void)

{

/* request auto detection */

int gdriver = DETECT, gmode, errorcode;

int left, top, right, bottom;

/* initialize graphics and local variables */

initgraph(&gdriver, &gmode, "");

/* read result of initialization */

errorcode = graphresult();

if (errorcode != grOk) /* an error occurred */

{

printf("Graphics error: %s\n", grapherrormsg(errorcode));

printf("Press any key to halt:");

getch();

exit(1); /* terminate with an error code */

}

left = getmaxx() / 2 - 50;

top = getmaxy() / 2 - 50;

right = getmaxx() / 2 + 50;

bottom = getmaxy() / 2 + 50;

/* draw a rectangle */

rectangle(left,top,right,bottom);

/* clean up */

getch();

closegraph();

return 0;

}

函数名: registerbgidriver

功能: 登录已连接进来的图形驱动程序代码

用法: int registerbgidriver(void(*driver)(void));

程序例:

#include ;

int main(void)

{

/* request auto detection */

int gdriver = DETECT, gmode, errorcode;

/* register a driver that was added into graphics.lib */

errorcode = registerbgidriver(EGAVGA_driver);

/* report any registration errors */

if (errorcode 函数名: remove

功能: 删除一个文件

用法: int remove(char *filename);

程序例:

#include ;

int main(void)

{

char file[80];

/* prompt for file name to delete */

printf("File to delete: ");

gets(file);

/* delete the file */

if (remove(file) == 0)

printf("Removed %s.\n",file);

else

perror("remove");

return 0;

}

函数名: rename

功能: 重命名文件

用法: int rename(char *oldname, char *newname);

程序例:

#include ;

int main(void)

{

char oldname[80], newname[80];

/* prompt for file to rename and new name */

printf("File to rename: ");

gets(oldname);

printf("New name: ");

gets(newname);

/* Rename the file */

if (rename(oldname, newname) == 0)

printf("Renamed %s to %s.\n", oldname, newname);

else

perror("rename");

return 0;

}

函数名: restorecrtmode

功能: 将屏幕模式恢复为先前的imitgraph设置

用法: void far restorecrtmode(void);

程序例:

#include ;

int main(void)

{

/* request auto detection */

int gdriver = DETECT, gmode, errorcode;

int x, y;

/* initialize graphics and local variables */

initgraph(&gdriver, &gmode, "");

/* read result of initialization */

errorcode = graphresult();

if (errorcode != grOk) /* an error occurred */

{

printf("Graphics error: %s\n", grapherrormsg(errorcode));

printf("Press any key to halt:");

getch();

exit(1); /* terminate with an error code */

}

x = getmaxx() / 2;

y = getmaxy() / 2;

/* output a message */

settextjustify(CENTER_TEXT, CENTER_TEXT);

outtextxy(x, y, "Press any key to exit graphics:");

getch();

/* restore system to text mode */

restorecrtmode();

printf("We're now in text mode.\n");

printf("Press any key to return to graphics mode:");

getch();

/* return to graphics mode */

setgraphmode(getgraphmode());

/* output a message */

settextjustify(CENTER_TEXT, CENTER_TEXT);

outtextxy(x, y, "We're back in graphics mode.");

outtextxy(x, y+textheight("W"), "Press any key to halt:");

/* clean up */

getch();

closegraph();

return 0;

}

函数名: rewind

功能: 将文件指针重新指向一个流的开头

用法: int rewind(FILE *stream);

程序例:

#include ;

int main(void)

{

FILE *fp;

char *fname = "TXXXXXX", *newname, first;

newname = mktemp(fname);

fp = fopen(newname,"w+");

fprintf(fp,"abcdefghijklmnopqrstuvwxyz");

rewind(fp);

fscanf(fp,"%c",&first);

printf("The first character is: %c\n",first);

fclose(fp);

remove(newname);

return 0;

}

函数名: rmdir

功能: 删除DOS文件目录

用法: int rmdir(char *stream);

程序例:

#include ;

#define DIRNAME "testdir.$$$"

int main(void)

{

int stat;

stat = mkdir(DIRNAME);

if (!stat)

printf("Directory created\n");

else

{

printf("Unable to create directory\n");

exit(1);

}

getch();

system("dir/p");

getch();

stat = rmdir(DIRNAME);

if (!stat)

printf("\nDirectory deleted\n");

else

{

perror("\nUnable to delete directory\n");

exit(1);

}

return 0;

}

CODE:

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函数名: sbrk

功能: 改变数据段空间位置

用法: char *sbrk(int incr);

程序例:

#include ;

int main(void)

{

printf("Changing allocation with sbrk()\n");

printf("Before sbrk() call: %lu bytes free\n",

(unsigned long) coreleft());

sbrk(1000);

printf(" After sbrk() call: %lu bytes free\n",

(unsigned long) coreleft());

return 0;

}

函数名: scanf

功能: 执行格式化输入

用法: int scanf(char *format[,argument,...]);

程序例:

#include ;

int main(void)

{

char label[20];

char name[20];

int entries = 0;

int loop, age;

double salary;

struct Entry_struct

{

char name[20];

int age;

float salary;

} entry[20];

/* Input a label as a string of characters restricting to 20 characters */

printf("\n\nPlease enter a label for the chart: ");

scanf("%20s", label);

fflush(stdin); /* flush the input stream in case of bad input */

/* Input number of entries as an integer */

printf("How many entries will there be? (less than 20) ");

scanf("%d", &entries);

fflush(stdin); /* flush the input stream in case of bad input */

/* input a name restricting input to only letters upper or lower case */

for (loop=0;loop函数名: searchpath

功能: 搜索DOS路径

用法: char *searchpath(char *filename);

程序例:

#include ;

int main(void)

{

char *p;

/* Looks for TLINK and returns a pointer

to the path */

p = searchpath("TLINK.EXE");

printf("Search for TLINK.EXE : %s\n", p);

/* Looks for non-existent file */

p = searchpath("NOTEXIST.FIL");

printf("Search for NOTEXIST.FIL : %s\n", p);

return 0;

}

函数名: sector

功能: 画并填充椭圆扇区

用法: void far sector(int x, int y, int stangle, int endangle);

程序例:

#include ;

int main(void)

{

/* request auto detection */

int gdriver = DETECT, gmode, errorcode;

int midx, midy, i;

int stangle = 45, endangle = 135;

int xrad = 100, yrad = 50;

/* initialize graphics and local variables */

initgraph(&gdriver, &gmode, "");

/* read result of initialization */

errorcode = graphresult();

if (errorcode != grOk) /* an error occurred */

{

printf("Graphics error: %s\n", grapherrormsg(errorcode));

printf("Press any key to halt:");

getch();

exit(1); /* terminate with an error code */

}

midx = getmaxx() / 2;

midy = getmaxy() / 2;

/* loop through the fill patterns */

for (i=EMPTY_FILL; i函数名: segread

功能: 读段寄存器值

用法: void segread(struct SREGS *segtbl);

程序例:

#include ;

int main(void)

{

struct SREGS segs;

segread(&segs);

printf("Current segment register settings\n\n");

printf("CS: %X DS: %X\n", segs.cs, segs.ds);

printf("ES: %X SS: %X\n", segs.es, segs.ss);

return 0;

}

函数名: setactivepage

功能: 设置图形输出活动页

用法: void far setactivepage(int pagenum);

程序例:

#include ;

int main(void)

{

/* select a driver and mode that supports */

/* multiple pages. */

int gdriver = EGA, gmode = EGAHI, errorcode;

int x, y, ht;

/* initialize graphics and local variables */

initgraph(&gdriver, &gmode, "");

/* read result of initialization */

errorcode = graphresult();

if (errorcode != grOk) /* an error occurred */

{

printf("Graphics error: %s\n", grapherrormsg(errorcode));

printf("Press any key to halt:");

getch();

exit(1); /* terminate with an error code */

}

x = getmaxx() / 2;

y = getmaxy() / 2;

ht = textheight("W");

/* select the off screen page for drawing */

setactivepage(1);

/* draw a line on page #1 */

line(0, 0, getmaxx(), getmaxy());

/* output a message on page #1 */

settextjustify(CENTER_TEXT, CENTER_TEXT);

outtextxy(x, y, "This is page #1:");

outtextxy(x, y+ht, "Press any key to halt:");

/* select drawing to page #0 */

setactivepage(0);

/* output a message on page #0 */

outtextxy(x, y, "This is page #0.");

outtextxy(x, y+ht, "Press any key to view page #1:");

getch();

/* select page #1 as the visible page */

setvisualpage(1);

/* clean up */

getch();

closegraph();

return 0;

}

函数名: setallpallette

功能: 按指定方式改变所有的调色板颜色

用法: void far setallpallette(struct palette, far *pallette);

程序例:

#include ;

int main(void)

{

/* request auto detection */

int gdriver = DETECT, gmode, errorcode;

struct palettetype pal;

int color, maxcolor, ht;

int y = 10;

char msg[80];

/* initialize graphics and local variables */

initgraph(&gdriver, &gmode, "");

/* read result of initialization */

errorcode = graphresult();

if (errorcode != grOk) /* an error occurred */

{

printf("Graphics error: %s\n", grapherrormsg(errorcode));

printf("Press any key to halt:");

getch();

exit(1); /* terminate with an error code */

}

maxcolor = getmaxcolor();

ht = 2 * textheight("W");

/* grab a copy of the palette */

getpalette(&pal);

/* display the default palette colors */

for (color=1; color函数名: setaspectratio

功能: 设置图形纵横比

用法: void far setaspectratio(int xasp, int yasp);

程序例:

#include ;

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();

if (errorcode != grOk) /* an error occurred */

{

printf("Graphics error: %s\n", grapherrormsg(errorcode));

printf("Press any key to halt:");

getch();

exit(1); /* terminate with an error code */

}

midx = getmaxx() / 2;

midy = getmaxy() / 2;

setcolor(getmaxcolor());

/* get current aspect ratio settings */

getaspectratio(&xasp, &yasp);

/* draw normal circle */

circle(midx, midy, 100);

getch();

/* claer the screen */

cleardevice();

/* adjust the aspect for a wide circle */

setaspectratio(xasp/2, yasp);

circle(midx, midy, 100);

getch();

/* adjust the aspect for a narrow circle */

cleardevice();

setaspectratio(xasp, yasp/2);

circle(midx, midy, 100);

/* clean up */

getch();

closegraph();

return 0;

}

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Linux C语言常用函数 04 | Linux C语言常用函数 06

2012-08-31 12:17
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