Linux C语言常用函数 04

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C和C++面试笔试题

函数名: hypot

功能: 计算直角三角形的斜边长

用法: double hypot(double x, double y);

程序例:

#include ;

int main(void)

{

double result;

double x = 3.0;

double y = 4.0;

result = hypot(x, y);

printf("The hypotenuse is: %lf\n", result);

return 0;

}

CODE:

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函数名: imagesize

功能: 返回保存位图像所需的字节数

用法: unsigned far imagesize(int left, int top, int right, int bottom);

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: initgraph

功能: 初始化图形系统

用法: void far initgraph(int far *graphdriver, int far *graphmode,

char far *pathtodriver);

程序例:

#include ;

int main(void)

{

/* request auto detection */

int gdriver = DETECT, gmode, errorcode;

/* initialize graphics mode */

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); /* return with error code */

}

/* draw a line */

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

/* clean up */

getch();

closegraph();

return 0;

}

函数名: inport

功能: 从硬件端口中输入

用法: int inp(int protid);

程序例:

#include ;

int main(void)

{

int result;

int port = 0; /* serial port 0 */

result = inport(port);

printf("Word read from port %d = 0x%X\n", port, result);

return 0;

}

函数名: insline

功能: 在文本窗口中插入一个空行

用法: void insline(void);

程序例:

#include ;

int main(void)

{

clrscr();

cprintf("INSLINE inserts an empty line in the text window\r\n");

cprintf("at the cursor position using the current text\r\n");

cprintf("background color. All lines below the empty one\r\n");

cprintf("move down one line and the bottom line scrolls\r\n");

cprintf("off the bottom of the window.\r\n");

cprintf("\r\nPress any key to continue:");

gotoxy(1, 3);

getch();

insline();

getch();

return 0;

}

函数名: installuserdriver

功能: 安装设备驱动程序到BGI设备驱动程序表中

用法: int far installuserdriver(char far *name, int (*detect)(void));

程序例:

#include ;

/* function prototypes */

int huge detectEGA(void);

void checkerrors(void);

int main(void)

{

int gdriver, gmode;

/* install a user written device driver */

gdriver = installuserdriver("EGA", detectEGA);

/* must force use of detection routine */

gdriver = DETECT;

/* check for any installation errors */

checkerrors();

/* initialize graphics and local variables */

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

/* check for any initialization errors */

checkerrors();

/* draw a line */

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

/* clean up */

getch();

closegraph();

return 0;

}

/* detects EGA or VGA cards */

int huge detectEGA(void)

{

int driver, mode, sugmode = 0;

detectgraph(&driver, &mode);

if ((driver == EGA) || (driver == VGA))

/* return suggested video mode number */

return sugmode;

else

/* return an error code */

return grError;

}

/* check for and report any graphics errors */

void checkerrors(void)

{

int errorcode;

/* read result of last graphics operation */

errorcode = graphresult();

if (errorcode != grOk)

{

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

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

getch();

exit(1);

}

函数名: installuserfont

功能: 安装未嵌入BGI系统的字体文件(CHR)

用法: int far installuserfont(char far *name);

程序例:

#include ;

/* function prototype */

void checkerrors(void);

int main(void)

{

/* request auto detection */

int gdriver = DETECT, gmode;

int userfont;

int midx, midy;

/* initialize graphics and local variables */

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

midx = getmaxx() / 2;

midy = getmaxy() / 2;

/* check for any initialization errors */

checkerrors();

/* install a user defined font file */

userfont = installuserfont("USER.CHR");

/* check for any installation errors */

checkerrors();

/* select the user font */

settextstyle(userfont, HORIZ_DIR, 4);

/* output some text */

outtextxy(midx, midy, "Testing!");

/* clean up */

getch();

closegraph();

return 0;

}

/* check for and report any graphics errors */

void checkerrors(void)

{

int errorcode;

/* read result of last graphics operation */

errorcode = graphresult();

if (errorcode != grOk)

{

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

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

getch();

exit(1);

}

函数名: int86

功能: 通用8086软中断接口

用法: int int86(int intr_num, union REGS *inregs, union REGS *outregs);

程序例:

#include ;

#define VIDEO 0x10

void movetoxy(int x, int y)

{

union REGS regs;

regs.h.ah = 2; /* set cursor postion */

regs.h.dh = y;

regs.h.dl = x;

regs.h.bh = 0; /* video page 0 */

int86(VIDEO, &s, &s);

}

int main(void)

{

clrscr();

movetoxy(35, 10);

printf("Hello\n");

return 0;

}

函数名: int86x

功能: 通用8086软中断接口

用法: int int86x(int intr_num, union REGS *insegs, union REGS *outregs,

struct SREGS *segregs);

程序例:

#include ;

int main(void)

{

char filename[80];

union REGS inregs, outregs;

struct SREGS segregs;

printf("Enter filename: ");

gets(filename);

inregs.h.ah = 0x43;

inregs.h.al = 0x21;

inregs.x.dx = FP_OFF(filename);

segregs.ds = FP_SEG(filename);

int86x(0x21, &inregs, &outregs, &segregs);

printf("File attribute: %X\n", outregs.x.cx);

return 0;

}

函数名: intdos

功能: 通用DOS接口

用法: int intdos(union REGS *inregs, union REGS *outregs);

程序例:

#include ;

/* deletes file name; returns 0 on success, nonzero on failure */

int delete_file(char near *filename)

{

union REGS regs;

int ret;

regs.h.ah = 0x41; /* delete file */

regs.x.dx = (unsigned) filename;

ret = intdos(&s, &s);

/* if carry flag is set, there was an error */

return(regs.x.cflag ? ret : 0);

}

int main(void)

{

int err;

err = delete_file("NOTEXIST.$$$");

if (!err)

printf("Able to delete NOTEXIST.$$$\n");

else

printf("Not Able to delete NOTEXIST.$$$\n");

return 0;

}

函数名: intdosx

功能: 通用DOS中断接口

用法: int intdosx(union REGS *inregs, union REGS *outregs,

struct SREGS *segregs);

程序例:

#include ;

/* deletes file name; returns 0 on success, nonzero on failure */

int delete_file(char far *filename)

{

union REGS regs; struct SREGS sregs;

int ret;

regs.h.ah = 0x41; /* delete file */

regs.x.dx = FP_OFF(filename);

sregs.ds = FP_SEG(filename);

ret = intdosx(&s, &s, &sregs);

/* if carry flag is set, there was an error */

return(regs.x.cflag ? ret : 0);

}

int main(void)

{

int err;

err = delete_file("NOTEXIST.$$$");

if (!err)

printf("Able to delete NOTEXIST.$$$\n");

else

printf("Not Able to delete NOTEXIST.$$$\n");

return 0;

}

函数名: intr

功能: 改变软中断接口

用法: void intr(int intr_num, struct REGPACK *preg);

程序例:

#include ;

#define CF 1 /* Carry flag */

int main(void)

{

char directory[80];

struct REGPACK reg;

printf("Enter directory to change to: ");

gets(directory);

reg.r_ax = 0x3B 函数名: ioctl

功能: 控制I/O设备

用法: int ioctl(int handle, int cmd[,int *argdx, int argcx]);

程序例:

#include ;

int main(void)

{

int stat;

/* use func 8 to determine if the default drive is removable */

stat = ioctl(0, 8, 0, 0);

if (!stat)

printf("Drive %c is removable.\n", getdisk() + 'A');

else

printf("Drive %c is not removable.\n", getdisk() + 'A');

return 0;

}

函数名: isatty

功能: 检查设备类型

用法: int isatty(int handle);

程序例:

#include ;

int main(void)

{

int handle;

handle = fileno(stdprn);

if (isatty(handle))

printf("Handle %d is a device type\n", handle);

else

printf("Handle %d isn't a device type\n", handle);

return 0;

}

函数名: itoa

功能: 把一整数转换为字符串

用法: char *itoa(int value, char *string, int radix);

程序例:

#include ;

int main(void)

{

int number = 12345;

char string[25];

itoa(number, string, 10);

printf("integer = %d string = %s\n", number, string);

return 0;

}

CODE:

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函数名: kbhit

功能: 检查当前按下的键

用法: int kbhit(void);

程序例:

#include ;

int main(void)

{

cprintf("Press any key to continue:");

while (!kbhit()) /* do nothing */ ;

cprintf("\r\nA key was pressed...\r\n");

return 0;

}

函数名: keep

功能: 退出并继续驻留

用法: void keep(int status, int size);

程序例:

/***NOTE:

This is an interrupt service routine. You

can NOT compile this program with Test

Stack Overflow turned on and get an

executable file which will operate

correctly. Due to the nature of this

function the formula used to compute

the number of paragraphs may not

necessarily work in all cases. Use with

care! Terminate Stay Resident (TSR)

programs are complex and no other support

for them is provided. Refer to the

MS-DOS technical documentation

for more information. */

#include ;

/* The clock tick interrupt */

#define INTR 0x1C

/* Screen attribute (blue on grey) */

#define ATTR 0x7900

/* reduce heaplength and stacklength

to make a smaller program in memory */

extern unsigned _heaplen = 1024;

extern unsigned _stklen = 512;

void interrupt ( *oldhandler)(void);

void interrupt handler(void)

{

unsigned int (far *screen)[80];

static int count;

/* For a color screen the video memory

is at B800:0000. For a monochrome

system use B000:000 */

screen = MK_FP(0xB800,0);

/* increase the counter and keep it

within 0 to 9 */

count++;

count %= 10;

/* put the number on the screen */

screen[0][79] = count + '0' + ATTR;

/* call the old interrupt handler */

oldhandler();

}

int main(void)

{

/* get the address of the current clock

tick interrupt */

oldhandler = getvect(INTR);

/* install the new interrupt handler */

setvect(INTR, handler);

/* _psp is the starting address of the

program in memory. The top of the stack

is the end of the program. Using _SS and

_SP together we can get the end of the

stack. You may want to allow a bit of

saftey space to insure that enough room

is being allocated ie:

(_SS + ((_SP + safety space)/16) - _psp)

keep(0, (_SS + (_SP/16) - _psp));

return 0;

}

main()主函数

每一C 程序都必须有一main()函数, 可以根据自己的爱好把它放在程序的某

个地方。有些程序员把它放在最前面, 而另一些程序员把它放在最后面, 无论放

在哪个地方, 以下几点说明都是适合的。

1. main() 参数

在Turbo C2.0启动过程中, 传递main()函数三个参数: argc, argv和env。

* argc: 整数, 为传给main()的命令行参数个数。

* argv: 字符串数组。

在DOS 3.X 版本中, argv[0] 为程序运行的全路径名; 对DOS 3.0

以下的版本, argv[0]为空串("") 。

argv[1] 为在DOS命令行中执行程序名后的第一个字符串;

argv[2] 为执行程序名后的第二个字符串;

...

argv[argc]为NULL。

*env: 安符串数组。env[] 的每一个元素都包含ENVVAR=value形式的字符

串。其中ENVVAR为环境变量如PATH或87。value 为ENVVAR的对应值如C:\DOS, C:

\TURBOC(对于PATH) 或YES(对于87)。

Turbo C2.0启动时总是把这三个参数传递给main()函数, 可以在用户程序中

说明(或不说明)它们, 如果说明了部分(或全部)参数, 它们就成为main()子程序

的局部变量。

请注意: 一旦想说明这些参数, 则必须按argc, argv, env 的顺序, 如以下

的例子:

main()

main(int argc)

main(int argc, char *argv[])

main(int argc, char *argv[], char *env[])

其中第二种情况是合法的, 但不常见, 因为在程序中很少有只用argc, 而不

用argv[]的情况。

以下提供一样例程序EXAMPLE.EXE, 演示如何在main()函数中使用三个参数:

/*program name EXAMPLE.EXE*/

#include ;

main(int argc, char *argv[], char *env[])

{

int i;

printf("These are the %d command- line arguments passed to

main:\n\n", argc);

for(i=0; i如果在DOS 提示符下, 按以下方式运行EXAMPLE.EXE:

C:\example first_argument "argument with blanks" 3 4 "last but

one" stop!

注意: 可以用双引号括起内含空格的参数, 如本例中的: " argument

with blanks"和"Last but one")。

结果是这样的:

The value of argc is 7

These are the 7 command-linearguments passed to main:

argv[0]:C:\TURBO\EXAMPLE.EXE

argv[1]:first_argument

argv[2]:argument with blanks

argv[3]:3

argv[4]:4

argv[5]:last but one

argv[6]:stop!

argv[7]NULL)

The environment string(s) on this system are:

env[0]: COMSPEC=C:\COMMAND.COM

env[1]: PROMPT=$P$G /*视具体设置而定*/

env[2]: PATH=C:\DOS;C:\TC /*视具体设置而定*/

应该提醒的是: 传送main() 函数的命令行参数的最大长度为128 个字符 (包

括参数间的空格), 这是由DOS 限制的。

函数名: matherr

功能: 用户可修改的数学错误处理程序

用法: int matherr(struct exception *e);

程序例:

/* This is a user-defined matherr function that prevents

any error messages from being printed. */

#include;

int matherr(struct exception *a)

{

return 1;

}

函数名: memccpy

功能: 从源source中拷贝n个字节到目标destin中

用法: void *memccpy(void *destin, void *source, unsigned char ch,

unsigned n);

程序例:

#include ;

int main(void)

{

char *src = "http://linux.chinaunix.net/techdoc/develop/2006/07/30/This is the source string";

char dest[50];

char *ptr;

ptr = memccpy(dest, src, 'c', strlen(src));

if (ptr)

{

*ptr = '\0';

printf("The character was found: %s\n", dest);

}

else

printf("The character wasn't found\n");

return 0;

}

函数名: malloc

功能: 内存分配函数

用法: void *malloc(unsigned size);

程序例:

#include ;

int main(void)

{

char *str;

/* allocate memory for string */

/* This will generate an error when compiling */

/* with C++, use the new operator instead. */

if ((str = malloc(10)) == NULL)

{

printf("Not enough memory to allocate buffer\n");

exit(1); /* terminate program if out of memory */

}

/* copy "Hello" into string */

strcpy(str, "Hello");

/* display string */

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

/* free memory */

free(str);

return 0;

}

函数名: memchr

功能: 在数组的前n个字节中搜索字符

用法: void *memchr(void *s, char ch, unsigned n);

程序例:

#include ;

int main(void)

{

char str[17];

char *ptr;

strcpy(str, "This is a string");

ptr = memchr(str, 'r', strlen(str));

if (ptr)

printf("The character 'r' is at position: %d\n", ptr - str);

else

printf("The character was not found\n");

return 0;

}

函数名: memcpy

功能: 从源source中拷贝n个字节到目标destin中

用法: void *memcpy(void *destin, void *source, unsigned n);

程序例:

#include ;

int main(void)

{

char src[] = "******************************";

char dest[] = "abcdefghijlkmnopqrstuvwxyz0123456709";

char *ptr;

printf("destination before memcpy: %s\n", dest);

ptr = memcpy(dest, src, strlen(src));

if (ptr)

printf("destination after memcpy: %s\n", dest);

else

printf("memcpy failed\n");

return 0;

}

函数名: memicmp

功能: 比较两个串s1和s2的前n个字节, 忽略大小写

用法: int memicmp(void *s1, void *s2, unsigned n);

程序例:

#include ;

int main(void)

{

char *buf1 = "ABCDE123";

char *buf2 = "abcde456";

int stat;

stat = memicmp(buf1, buf2, 5);

printf("The strings to position 5 are ");

if (stat)

printf("not ");

printf("the same\n");

return 0;

}

函数名: memmove

功能: 移动一块字节

用法: void *memmove(void *destin, void *source, unsigned n);

程序例:

#include ;

int main(void)

{

char *dest = "abcdefghijklmnopqrstuvwxyz0123456789";

char *src = "http://linux.chinaunix.net/techdoc/develop/2006/07/30/******************************";

printf("destination prior to memmove: %s\n", dest);

memmove(dest, src, 26);

printf("destination after memmove: %s\n", dest);

return 0;

}

函数名: memset

功能: 设置s中的所有字节为ch, s数组的大小由n给定

用法: void *memset(void *s, char ch, unsigned n);

程序例:

#include ;

int main(void)

{

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

printf("Buffer before memset: %s\n", buffer);

memset(buffer, '*', strlen(buffer) - 1);

printf("Buffer after memset: %s\n", buffer);

return 0;

}

函数名: mkdir

功能: 建立一个目录

用法: int mkdir(char *pathname);

程序例:

#include ;

int main(void)

{

int status;

clrscr();

status = mkdir("asdfjklm");

(!status) ? (printf("Directory created\n")) :

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

getch();

system("dir");

getch();

status = rmdir("asdfjklm");

(!status) ? (printf("Directory deleted\n")) :

(perror("Unable to delete directory"));

return 0;

}

函数名: mktemp

功能: 建立唯一的文件名

用法: char *mktemp(char *template);

程序例:

#include ;

int main(void)

{

/* fname defines the template for the

temporary file. */

char *fname = "TXXXXXX", *ptr;

ptr = mktemp(fname);

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

return 0;

}

函数名: MK_FP

功能: 设置一个远指针

用法: void far *MK_FP(unsigned seg, unsigned off);

程序例:

#include ;

int main(void)

{

int gd, gm, i;

unsigned int far *screen;

detectgraph(&gd, &gm);

if (gd == HERCMONO)

screen = MK_FP(0xB000, 0);

else

screen = MK_FP(0xB800, 0);

for (i=0; i函数名: modf

功能: 把数分为指数和尾数

用法: double modf(double value, double *iptr);

程序例:

#include ;

int main(void)

{

double fraction, integer;

double number = 100000.567;

fraction = modf(number, &integer);

printf("The whole and fractional parts of %lf are %lf and %lf\n",

number, integer, fraction);

return 0;

}

函数名: movedata

功能: 拷贝字节

用法: void movedata(int segsrc, int offsrc, int segdest,

int offdest, unsigned numbytes);

程序例:

#include ;

#define MONO_BASE 0xB000

/* saves the contents of the monochrome screen in buffer */

void save_mono_screen(char near *buffer)

{

movedata(MONO_BASE, 0, _DS, (unsigned)buffer, 80*25*2);

}

int main(void)

{

char buf[80*25*2];

save_mono_screen(buf);

}

函数名: moverel

功能: 将当前位置(CP)移动一相对距离

用法: void far moverel(int dx, int dy);

程序例:

#include ;

int main(void)

{

/* request auto detection */

int gdriver = DETECT, gmode, errorcode;

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 */

}

/* move the C.P. to location (20, 30) */

moveto(20, 30);

/* plot a pixel at the C.P. */

putpixel(getx(), gety(), getmaxcolor());

/* create and output a message at (20, 30) */

sprintf(msg, " (%d, %d)", getx(), gety());

outtextxy(20, 30, msg);

/* move to a point a relative distance */

/* away from the current value of C.P. */

moverel(100, 100);

/* plot a pixel at the C.P. */

putpixel(getx(), gety(), getmaxcolor());

/* create and output a message at C.P. */

sprintf(msg, " (%d, %d)", getx(), gety());

outtext(msg);

/* clean up */

getch();

closegraph();

return 0;

}

函数名: movetext

功能: 将屏幕文本从一个矩形区域拷贝到另一个矩形区域

用法: int movetext(int left, int top, int right, int bottom,

int newleft, int newtop);

程序例:

#include ;

int main(void)

{

char *str = "This is a test string";

clrscr();

cputs(str);

getch();

movetext(1, 1, strlen(str), 2, 10, 10);

getch();

return 0;

}

函数名: moveto

功能: 将CP移到(x, y)

用法: void far moveto(int x, int y);

程序例:

#include ;

int main(void)

{

/* request auto detection */

int gdriver = DETECT, gmode, errorcode;

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 */

}

/* move the C.P. to location (20, 30) */

moveto(20, 30);

/* plot a pixel at the C.P. */

putpixel(getx(), gety(), getmaxcolor());

/* create and output a message at (20, 30) */

sprintf(msg, " (%d, %d)", getx(), gety());

outtextxy(20, 30, msg);

/* move to (100, 100) */

moveto(100, 100);

/* plot a pixel at the C.P. */

putpixel(getx(), gety(), getmaxcolor());

/* create and output a message at C.P. */

sprintf(msg, " (%d, %d)", getx(), gety());

outtext(msg);

/* clean up */

getch();

closegraph();

return 0;

}

函数名: movemem

功能: 移动一块字节

用法: void movemem(void *source, void *destin, unsigned len);

程序例:

#include ;

int main(void)

{

char *source = "Borland International";

char *destination;

int length;

length = strlen(source);

destination = malloc(length + 1);

movmem(source,destination,length);

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

return 0;

}

函数名: normvideo

功能: 选择正常亮度字符

用法: void normvideo(void);

程序例:

#include ;

int main(void)

{

normvideo();

cprintf("NORMAL Intensity Text\r\n");

return 0;

}

函数名: nosound

功能: 关闭PC扬声器

用法: void nosound(void);

程序例:

/* Emits a 7-Hz tone for 10 seconds.

True story: 7 Hz is the resonant frequency of a chicken's skull cavity.

This was determined empirically in Australia, where a new factory

generating 7-Hz tones was located too close to a chicken ranch:

When the factory started up, all the chickens died.

Your PC may not be able to emit a 7-Hz tone.

int main(void)

{

sound(7);

delay(10000);

nosound();

}

CODE:

[Copy to clipboard]

函数名: open

功能: 打开一个文件用于读或写

用法: int open(char *pathname, int access[, int permiss]);

程序例:

#include ;

int main(void)

{

int handle;

char msg[] = "Hello world";

if ((handle = open("TEST.$$$", O_CREAT | O_TEXT)) == -1)

{

perror("Error:");

return 1;

}

write(handle, msg, strlen(msg));

close(handle);

return 0;

}

函数名: outport

功能: 输出整数到硬件端口中

用法: void outport(int port, int value);

程序例:

#include ;

int main(void)

{

int value = http://linux.chinaunix.net/techdoc/develop/2006/07/30/64;

int port = 0;

outportb(port, value);

printf("Value %d sent to port number %d\n", value, port);

return 0;

}

函数名: outportb

功能: 输出字节到硬件端口中

用法: void outportb(int port, char byte);

程序例:

#include ;

int main(void)

{

int value = http://linux.chinaunix.net/techdoc/develop/2006/07/30/64;

int port = 0;

outportb(port, value);

printf("Value %d sent to port number %d\n", value, port);

return 0;

}

函数名: outtext

功能: 在视区显示一个字符串

用法: void far outtext(char far *textstring);

程序例:

#include ;

int main(void)

{

/* request auto detection */

int gdriver = DETECT, gmode, errorcode;

int 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;

/* move the C.P. to the center of the screen */

moveto(midx, midy);

/* output text starting at the C.P. */

outtext("This ");

outtext("is ");

outtext("a ");

outtext("test.");

/* clean up */

getch();

closegraph();

return 0;

}

函数名: outtextxy

功能: 在指定位置显示一字符串

用法: void far outtextxy(int x, int y, char *textstring);

程序例:

#include ;

int main(void)

{

/* request auto detection */

int gdriver = DETECT, gmode, errorcode;

int 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;

/* output text at the center of the screen*/

/* Note: the C.P. doesn't get changed.*/

outtextxy(midx, midy, "This is a test.");

/* clean up */

getch();

closegraph();

return 0;

}

函数名: parsfnm

功能: 分析文件名

用法: char *parsfnm (char *cmdline, struct fcb *fcbptr, int option);

程序例:

#include ;

int main(void)

{

char line[80];

struct fcb blk;

/* get file name */

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

gets(line);

/* put file name in fcb */

if (parsfnm(line, &blk, 1) == NULL)

printf("Error in parsfm call\n");

else

printf("Drive #%d Name: %11s\n", blk.fcb_drive, blk.fcb_name);

return 0;

}

函数名: peek

功能: 检查存储单元

用法: int peek(int segment, unsigned offset);

程序例:

#include ;

int main(void)

{

int value = http://linux.chinaunix.net/techdoc/develop/2006/07/30/0;

printf("The current status of your keyboard is:\n");

value = http://linux.chinaunix.net/techdoc/develop/2006/07/30/peek(0x0040, 0x0017);

if (value & 1)

printf("Right shift on\n");

else

printf("Right shift off\n");

if (value & 2)

printf("Left shift on\n");

else

printf("Left shift off\n");

if (value & 4)

printf("Control key on\n");

else

printf("Control key off\n");

if (value & 8)

printf("Alt key on\n");

else

printf("Alt key off\n");

if (value & 16)

printf("Scroll lock on\n");

else

printf("Scroll lock off\n");

if (value & 32)

printf("Num lock on\n");

else

printf("Num lock off\n");

if (value & 64)

printf("Caps lock on\n");

else

printf("Caps lock off\n");

return 0;

}

函数名: peekb

功能: 检查存储单元

用法: char peekb (int segment, unsigned offset);

程序例:

#include ;

int main(void)

{

int value = http://linux.chinaunix.net/techdoc/develop/2006/07/30/0;

printf("The current status of your keyboard is:\n");

value = http://linux.chinaunix.net/techdoc/develop/2006/07/30/peekb(0x0040, 0x0017);

if (value & 1)

printf("Right shift on\n");

else

printf("Right shift off\n");

if (value & 2)

printf("Left shift on\n");

else

printf("Left shift off\n");

if (value & 4)

printf("Control key on\n");

else

printf("Control key off\n");

if (value & 8)

printf("Alt key on\n");

else

printf("Alt key off\n");

if (value & 16)

printf("Scroll lock on\n");

else

printf("Scroll lock off\n");

if (value & 32)

printf("Num lock on\n");

else

printf("Num lock off\n");

if (value & 64)

printf("Caps lock on\n");

else

printf("Caps lock off\n");

return 0;

}

函数名: perror

功能: 系统错误信息

用法: void perror(char *string);

程序例:

#include ;

int main(void)

{

FILE *fp;

fp = fopen("perror.dat", "r");

if (!fp)

perror("Unable to open file for reading");

return 0;

}

函数名: pieslice

功能: 绘制并填充一个扇形

用法: void far pieslice(int x, int stanle, int endangle, int radius);

程序例:

#include ;

int main(void)

{

/* request auto detection */

int gdriver = DETECT, gmode, errorcode;

int midx, midy;

int stangle = 45, endangle = 135, radius = 100;

/* 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;

/* set fill style and draw a pie slice */

setfillstyle(EMPTY_FILL, getmaxcolor());

pieslice(midx, midy, stangle, endangle, radius);

/* clean up */

getch();

closegraph();

return 0;

}

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Linux C语言常用函数 03 | Linux C语言常用函数 05

2012-08-31 12:17
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