Linux C语言常用函数 01

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C和C++面试笔试题

函数名: abort

功能: 异常终止一个进程

用法: void abort(void);

程序例:

#include ;

int main(void)

{

printf("Calling abort()\n");

abort();

return 0; /* This is never reached */

}

函数名: abs

功能: 求整数的绝对值

用法: int abs(int i);

程序例:

#include ;

int main(void)

{

int number = -1234;

printf("number: %d absolute value: %d\n", number, abs(number));

return 0;

}

函数名: absread, abswirte

功能: 绝对磁盘扇区读、写数据

用法: int absread(int drive, int nsects, int sectno, void *buffer);

int abswrite(int drive, int nsects, in tsectno, void *buffer);

程序例:

/* absread example */

#include ;

int main(void)

{

int i, strt, ch_out, sector;

char buf[512];

printf("Insert a diskette into drive A and press any key\n");

getch();

sector = 0;

if (absread(0, 1, sector, &buf) != 0)

{

perror("Disk problem");

exit(1);

}

printf("Read OK\n");

strt = 3;

for (i=0; i

函数名: access

功能: 确定文件的访问权限

用法: int access(const char *filename, int amode);

程序例:

#include ;

int file_exists(char *filename);

int main(void)

{

printf("Does NOTEXIST.FIL exist: %s\n",

file_exists("NOTEXISTS.FIL") ? "YES" : "NO");

return 0;

}

int file_exists(char *filename)

{

return (access(filename, 0) == 0);

}

函数名: acos

功能: 反余弦函数

用法: double acos(double x);

程序例:

#include ;

int main(void)

{

double result;

double x = 0.5;

result = acos(x);

printf("The arc cosine of %lf is %lf\n", x, result);

return 0;

}

函数名: allocmem

功能: 分配DOS存储段

用法: int allocmem(unsigned size, unsigned *seg);

程序例:

#include ;

int main(void)

{

unsigned int size, segp;

int stat;

size = 64; /* (64 x 16) = 1024 bytes */

stat = allocmem(size, &segp);

if (stat == -1)

printf("Allocated memory at segment: %x\n", segp);

else

printf("Failed: maximum number of paragraphs available is %u\n",

stat);

return 0;

}

函数名: arc

功能: 画一弧线

用法: void far arc(int x, int y, int stangle, 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;

int radius = 100;

/* 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("ress any key to halt:");

getch();

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

}

midx = getmaxx() / 2;

midy = getmaxy() / 2;

setcolor(getmaxcolor());

/* draw arc */

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

/* clean up */

getch();

closegraph();

return 0;

}

函数名: asctime

功能: 转换日期和时间为ASCII码

用法: char *asctime(const struct tm *tblock);

程序例:

#include ;

int main(void)

{

struct tm t;

char str[80];

/* sample loading of tm structure */

t.tm_sec = 1; /* Seconds */

t.tm_min = 30; /* Minutes */

t.tm_hour = 9; /* Hour */

t.tm_mday = 22; /* Day of the Month */

t.tm_mon = 11; /* Month */

t.tm_year = 56; /* Year - does not include century */

t.tm_wday = 4; /* Day of the week */

t.tm_yday = 0; /* Does not show in asctime */

t.tm_isdst = 0; /* Is Daylight SavTime; does not show in asctime */

/* converts structure to null terminated

string */

strcpy(str, asctime(&t));

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

return 0;

}

函数名: asin

功能: 反正弦函数

用法: double asin(double x);

程序例:

#include ;

int main(void)

{

double result;

double x = 0.5;

result = asin(x);

printf("The arc sin of %lf is %lf\n", x, result);

return(0);

}

函数名: assert

功能: 测试一个条件并可能使程序终止

用法: void assert(int test);

程序例:

#include ;

struct ITEM {

int key;

int value;

};

/* add item to list, make sure list is not null */

void additem(struct ITEM *itemptr) {

assert(itemptr != NULL);

/* add item to list */

}

int main(void)

{

additem(NULL);

return 0;

}

函数名: atan

功能: 反正切函数

用法: double atan(double x);

程序例:

#include ;

int main(void)

{

double result;

double x = 0.5;

result = atan(x);

printf("The arc tangent of %lf is %lf\n", x, result);

return(0);

}

函数名: atan2

功能: 计算Y/X的反正切值

用法: double atan2(double y, double x);

程序例:

#include ;

int main(void)

{

double result;

double x = 90.0, y = 45.0;

result = atan2(y, x);

printf("The arc tangent ratio of %lf is %lf\n", (y / x), result);

return 0;

}

函数名: atexit

功能: 注册终止函数

用法: int atexit(atexit_t func);

程序例:

#include ;

void exit_fn1(void)

{

printf("Exit function #1 called\n");

}

void exit_fn2(void)

{

printf("Exit function #2 called\n");

}

int main(void)

{

/* post exit function #1 */

atexit(exit_fn1);

/* post exit function #2 */

atexit(exit_fn2);

return 0;

}

函数名: atof

功能: 把字符串转换成浮点数

用法: double atof(const char *nptr);

程序例:

#include ;

int main(void)

{

float f;

char *str = "12345.67";

f = atof(str);

printf("string = %s float = %f\n", str, f);

return 0;

}

函数名: atoi

功能: 把字符串转换成int数

用法: int atoi(const char *nptr);

程序例:

#include ;

int main(void)

{

int n;

char *str = "12345.67";

n = atoi(str);

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

return 0;

}

函数名: atol

功能: 把字符串转换成长整型数

用法: long atol(const char *nptr);

程序例:

#include ;

int main(void)

{

long l;

char *str = "98765432";

l = atol(lstr);

printf("string = %s integer = %ld\n", str, l);

return(0);

}

函数名: bar

功能: 画一个二维条形图

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

程序例:

#include ;

int main(void)

{

/* request auto detection */

int gdriver = DETECT, gmode, errorcode;

int midx, midy, i;

/* 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("ress 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=SOLID_FILL; i函数名: bar3d

功能: 画一个三维条形图

用法: void far bar3d(int left, int top, int right, int bottom,

int depth, int topflag);

程序例:

#include ;

int main(void)

{

/* request auto detection */

int gdriver = DETECT, gmode, errorcode;

int midx, midy, i;

/* initialize graphics, 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("ress any key to halt:");

getch();

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

}

midx = getmaxx() / 2;

midy = getmaxy() / 2;

/* loop through the fill patterns */

for (i=EMPTY_FILL; i函数名: bdos

功能: DOS系统调用

用法: int bdos(int dosfun, unsigned dosdx, unsigned dosal);

程序例:

#include ;

/* Get current drive as 'A', 'B', ... */

char current_drive(void)

{

char curdrive;

/* Get current disk as 0, 1, ... */

curdrive = bdos(0x19, 0, 0);

return('A' + curdrive);

}

int main(void)

{

printf("The current drive is %c:\n", current_drive());

return 0;

}

函数名: bdosptr

功能: DOS系统调用

用法: int bdosptr(int dosfun, void *argument, unsigned dosal);

程序例:

#include ;

#define BUFLEN 80

int main(void)

{

char buffer[BUFLEN];

int test;

printf("Enter full pathname of a directory\n");

gets(buffer);

test = bdosptr(0x3B,buffer,0);

if(test)

{

printf("DOS error message: %d\n", errno);

/* See errno.h for error listings */

exit (1);

}

getcwd(buffer, BUFLEN);

printf("The current directory is: %s\n", buffer);

return 0;

}

函数名: bioscom

功能: 串行I/O通信

用法: int bioscom(int cmd, char abyte, int port);

程序例:

#include ;

#define COM1 0

#define DATA_READY 0x100

#define TRUE 1

#define FALSE 0

#define SETTINGS ( 0x80 | 0x02 | 0x00 | 0x00)

int main(void)

{

int in, out, status, DONE = FALSE;

bioscom(0, SETTINGS, COM1);

cprintf("... BIOSCOM [ESC] to exit ...\n");

while (!DONE)

{

status = bioscom(3, 0, COM1);

if (status & DATA_READY)

if ((out = bioscom(2, 0, COM1) & 0x7F) != 0)

putch(out);

if (kbhit())

{

if ((in = getch()) == '\x1B')

DONE = TRUE;

bioscom(1, in, COM1);

}

return 0;

}

函数名: biosdisk

功能: 软硬盘I/O

用法: int biosdisk(int cmd, int drive, int head, int track, int sector

int nsects, void *buffer);

程序例:

#include ;

int main(void)

{

int result;

char buffer[512];

printf("Testing to see if drive a: is ready\n");

result = biosdisk(4,0,0,0,0,1,buffer);

result &= 0x02;

(result) ? (printf("Drive A: Ready\n")) :

(printf("Drive A: Not Ready\n"));

return 0;

}

函数名: biosequip

功能: 检查设备

用法: int biosequip(void);

程序例:

#include ;

int main(void)

{

int result;

char buffer[512];

printf("Testing to see if drive a: is ready\n");

result = biosdisk(4,0,0,0,0,1,buffer);

result &= 0x02;

(result) ? (printf("Drive A: Ready\n")) :

(printf("Drive A: Not Ready\n"));

return 0;

}

函数名: bioskey

功能: 直接使用BIOS服务的键盘接口

用法: int bioskey(int cmd);

程序例:

#include ;

#define RIGHT 0x01

#define LEFT 0x02

#define CTRL 0x04

#define ALT 0x08

int main(void)

{

int key, modifiers;

/* function 1 returns 0 until a key is pressed */

while (bioskey(1) == 0);

/* function 0 returns the key that is waiting */

key = bioskey(0);

/* use function 2 to determine if shift keys were used */

modifiers = bioskey(2);

if (modifiers)

{

printf("[");

if (modifiers & RIGHT) printf("RIGHT");

if (modifiers & LEFT) printf("LEFT");

if (modifiers & CTRL) printf("CTRL");

if (modifiers & ALT) printf("ALT");

printf("]");

}

/* print out the character read */

if (isalnum(key & 0xFF))

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

else

printf("%#02x\n", key);

return 0;

}

函数名: biosmemory

功能: 返回存储块大小

用法:int biosmemory(void);

程序例:

#include ;

int main(void)

{

int memory_size;

memory_size = biosmemory(); /* returns value up to 640K */

printf("RAM size = %dK\n",memory_size);

return 0;

}

函数名: biosprint

功能: 直接使用BIOS服务的打印机I/O

用法: int biosprint(int cmd, int byte, int port);

程序例:

#include ;

int main(void)

{

#define STATUS 2 /* printer status command */

#define PORTNUM 0 /* port number for LPT1 */

int status, abyte=0;

printf("lease turn off your printer. Press any key to continue\n");

getch();

status = biosprint(STATUS, abyte, PORTNUM);

if (status & 0x01)

printf("Device time out.\n");

if (status & 0x08)

printf("I/O error.\n");

if (status & 0x10)

printf("Selected.\n");

if (status & 0x20)

printf("Out of paper.\n");

if (status & 0x40)

printf("Acknowledge.\n");

if (status & 0x80)

printf("Not busy.\n");

return 0;

}

函数名: biostime

功能: 读取或设置BIOS时间

用法: long biostime(int cmd, long newtime);

程序例:

#include ;

int main(void)

{

long bios_time;

clrscr();

cprintf("The number of clock ticks since midnight is:\r\n");

cprintf("The number of seconds since midnight is:\r\n");

cprintf("The number of minutes since midnight is:\r\n");

cprintf("The number of hours since midnight is:\r\n");

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

while(!kbhit())

{

bios_time = biostime(0, 0L);

gotoxy(50, 1);

cprintf("%lu", bios_time);

gotoxy(50, 2);

cprintf("%.4f", bios_time / CLK_TCK);

gotoxy(50, 3);

cprintf("%.4f", bios_time / CLK_TCK / 60);

gotoxy(50, 4);

cprintf("%.4f", bios_time / CLK_TCK / 3600);

}

return 0;

}

函数名: brk

功能: 改变数据段空间分配

用法: int brk(void *endds);

程序例:

#include ;

int main(void)

{

char *ptr;

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

ptr = malloc(1);

printf("Before brk() call: %lu bytes free\n", coreleft());

brk(ptr+1000);

printf(" After brk() call: %lu bytes free\n", coreleft());

return 0;

}

函数名: bsearch

功能: 二分法搜索

用法: void *bsearch(const void *key, const void *base, size_t *nelem,

size_t width, int(*fcmp)(const void *, const *));

程序例:

#include ;

#define NELEMS(arr) (sizeof(arr) / sizeof(arr[0]))

int numarray[] = {123, 145, 512, 627, 800, 933};

int numeric (const int *p1, const int *p2)

{

return(*p1 - *p2);

}

int lookup(int key)

{

int *itemptr;

/* The cast of (int(*)(const void *,const void*))

is needed to avoid a type mismatch error at

compile time */

itemptr = bsearch (&key, numarray, NELEMS(numarray),

sizeof(int), (int(*)(const void *,const void *))numeric);

return (itemptr != NULL);

}

int main(void)

{

if (lookup(512))

printf("512 is in the table.\n");

else

printf("512 isn't in the table.\n");

return 0;

}

函数名: cabs

功能: 计算复数的绝对值

用法: double cabs(struct complex z);

程序例:

#include ;

int main(void)

{

struct complex z;

double val;

z.x = 2.0;

z.y = 1.0;

val = cabs(z);

printf("The absolute value of %.2lfi %.2lfj is %.2lf", z.x, z.y, val);

return 0;

}

函数名: calloc

功能: 分配主存储器

用法: void *calloc(size_t nelem, size_t elsize);

程序例:

#include ;

int main(void)

{

char *str = NULL;

/* allocate memory for string */

str = calloc(10, sizeof(char));

/* copy "Hello" into string */

strcpy(str, "Hello");

/* display string */

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

/* free memory */

free(str);

return 0;

}

函数名: ceil

功能: 向上舍入

用法: double ceil(double x);

程序例:

#include ;

int main(void)

{

double number = 123.54;

double down, up;

down = floor(number);

up = ceil(number);

printf("original number %5.2lf\n", number);

printf("number rounded down %5.2lf\n", down);

printf("number rounded up %5.2lf\n", up);

return 0;

}

函数名: cgets

功能: 从控制台读字符串

用法: char *cgets(char *str);

程序例:

#include ;

int main(void)

{

char buffer[83];

char *p;

/* There's space for 80 characters plus the NULL terminator */

buffer[0] = 81;

printf("Input some chars:");

p = cgets(buffer);

printf("\ncgets read %d characters: \"%s\"\n", buffer[1], p);

printf("The returned pointer is %p, buffer[0] is at %p\n", p, &buffer);

/* Leave room for 5 characters plus the NULL terminator */

buffer[0] = 6;

printf("Input some chars:");

p = cgets(buffer);

printf("\ncgets read %d characters: \"%s\"\n", buffer[1], p);

printf("The returned pointer is %p, buffer[0] is at %p\n", p, &buffer);

return 0;

}

函数名: chdir

功能: 改变工作目录

用法: int chdir(const char *path);

程序例:

#include ;

char old_dir[MAXDIR];

char new_dir[MAXDIR];

int main(void)

{

if (getcurdir(0, old_dir))

{

perror("getcurdir()");

exit(1);

}

printf("Current directory is: \\%s\n", old_dir);

if (chdir("\\"))

{

perror("chdir()");

exit(1);

}

if (getcurdir(0, new_dir))

{

perror("getcurdir()");

exit(1);

}

printf("Current directory is now: \\%s\n", new_dir);

printf("\nChanging back to orignal directory: \\%s\n", old_dir);

if (chdir(old_dir))

{

perror("chdir()");

exit(1);

}

return 0;

}

函数名: _chmod, chmod

功能: 改变文件的访问方式

用法: int chmod(const char *filename, int permiss);

程序例:

#include ;

void make_read_only(char *filename);

int main(void)

{

make_read_only("NOTEXIST.FIL");

make_read_only("MYFILE.FIL");

return 0;

}

void make_read_only(char *filename)

{

int stat;

stat = chmod(filename, S_IREAD);

if (stat)

printf("Couldn't make %s read-only\n", filename);

else

printf("Made %s read-only\n", filename);

}

函数名: chsize

功能: 改变文件大小

用法: int chsize(int handle, long size);

程序例:

#include ;

int main(void)

{

int handle;

char buf[11] = "0123456789";

/* create text file containing 10 bytes */

handle = open("DUMMY.FIL", O_CREAT);

write(handle, buf, strlen(buf));

/* truncate the file to 5 bytes in size */

chsize(handle, 5);

/* close the file */

close(handle);

return 0;

}

函数名: circle

功能: 在给定半径以(x, y)为圆心画圆

用法: void far circle(int x, int y, int radius);

程序例:

#include ;

int main(void)

{

/* request auto detection */

int gdriver = DETECT, gmode, errorcode;

int midx, midy;

int 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("ress any key to halt:");

getch();

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

}

midx = getmaxx() / 2;

midy = getmaxy() / 2;

setcolor(getmaxcolor());

/* draw the circle */

circle(midx, midy, radius);

/* clean up */

getch();

closegraph();

return 0;

}

函数名: cleardevice

功能: 清除图形屏幕

用法: void far cleardevice(void);

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("ress any key to halt:");

getch();

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

}

midx = getmaxx() / 2;

midy = getmaxy() / 2;

setcolor(getmaxcolor());

/* for centering screen messages */

settextjustify(CENTER_TEXT, CENTER_TEXT);

/* output a message to the screen */

outtextxy(midx, midy, "press any key to clear the screen:");

/* wait for a key */

getch();

/* clear the screen */

cleardevice();

/* output another message */

outtextxy(midx, midy, "press any key to quit:");

/* clean up */

getch();

closegraph();

return 0;

}

函数名: clearerr

功能: 复位错误标志

用法:void clearerr(FILE *stream);

程序例:

#include ;

int main(void)

{

FILE *fp;

char ch;

/* open a file for writing */

fp = fopen("DUMMY.FIL", "w");

/* force an error condition by attempting to read */

ch = fgetc(fp);

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

if (ferror(fp))

{

/* display an error message */

printf("Error reading from DUMMY.FIL\n");

/* reset the error and EOF indicators */

clearerr(fp);

}

fclose(fp);

return 0;

}

函数名: clearviewport

功能: 清除图形视区

用法: void far clearviewport(void);

程序例:

#include ;

#define CLIP_ON 1 /* activates clipping in viewport */

int main(void)

{

/* request auto detection */

int gdriver = DETECT, gmode, errorcode;

int 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("ress any key to halt:");

getch();

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

}

setcolor(getmaxcolor());

ht = textheight("W");

/* message in default full-screen viewport */

outtextxy(0, 0, "* 函数名: _close, close

功能: 关闭文件句柄

用法: int close(int handle);

程序例:

#include ;

main()

{

int handle;

char buf[11] = "0123456789";

/* create a file containing 10 bytes */

handle = open("NEW.FIL", O_CREAT);

if (handle >; -1)

{

write(handle, buf, strlen(buf));

/* close the file */

close(handle);

}

else

{

printf("Error opening file\n");

}

return 0;

}

函数名: clock

功能: 确定处理器时间

用法: clock_t clock(void);

程序例:

#include ;

int main(void)

{

clock_t start, end;

start = clock();

delay(2000);

end = clock();

printf("The time was: %f\n", (end - start) / CLK_TCK);

return 0;

}

函数名: closegraph

功能: 关闭图形系统

用法: void far closegraph(void);

程序例:

#include ;

int main(void)

{

/* request auto detection */

int gdriver = DETECT, gmode, errorcode;

int x, y;

/* 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("ress 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, "ress a key to close the graphics system:");

/* wait for a key */

getch();

/* closes down the graphics system */

closegraph();

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

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

getch();

return 0;

}

函数名: clreol

功能: 在文本窗口中清除字符到行末

用法: void clreol(void);

程序例:

#include ;

int main(void)

{

clrscr();

cprintf("The function CLREOL clears all characters from the\r\n");

cprintf("cursor position to the end of the line within the\r\n");

cprintf("current text window, without moving the cursor.\r\n");

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

gotoxy(14, 4);

getch();

clreol();

getch();

return 0;

}

函数名: clrscr

功能: 清除文本模式窗口

用法: void clrscr(void);

程序例:

#include ;

int main(void)

{

int i;

clrscr();

for (i = 0; i 函数名: coreleft

功能: 返回未使用内存的大小

用法: unsigned coreleft(void);

程序例:

#include ;

int main(void)

{

printf("The difference between the highest allocated block and\n");

printf("the top of the heap is: %lu bytes\n", (unsigned long) coreleft());

return 0;

}

函数名: cos

功能: 余弦函数

用法: double cos(double x);

程序例:

#include ;

int main(void)

{

double result;

double x = 0.5;

result = cos(x);

printf("The cosine of %lf is %lf\n", x, result);

return 0;

}

函数名: cosh

功能: 双曲余弦函数

用法: dluble cosh(double x);

程序例:

#include ;

int main(void)

{

double result;

double x = 0.5;

result = cosh(x);

printf("The hyperboic cosine of %lf is %lf\n", x, result);

return 0;

}

函数名: country

功能: 返回与国家有关的信息

用法: struct COUNTRY *country(int countrycode, struct country *country);

程序例:

#include ;

#define USA 0

int main(void)

{

struct COUNTRY country_info;

country(USA, &country_info);

printf("The currency symbol for the USA is: %s\n",

country_info.co_curr);

return 0;

}

函数名: cprintf

功能: 送格式化输出至屏幕

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

程序例:

#include ;

int main(void)

{

/* clear the screen */

clrscr();

/* create a text window */

window(10, 10, 80, 25);

/* output some text in the window */

cprintf("Hello world\r\n");

/* wait for a key */

getch();

return 0;

}

函数名: cputs

功能: 写字符到屏幕

用法: void cputs(const char *string);

程序例:

#include ;

int main(void)

{

/* clear the screen */

clrscr();

/* create a text window */

window(10, 10, 80, 25);

/* output some text in the window */

cputs("This is within the window\r\n");

/* wait for a key */

getch();

return 0;

}

函数名: _creat creat

功能: 创建一个新文件或重写一个已存在的文件

用法: int creat (const char *filename, int permiss);

程序例:

#include ;

int main(void)

{

int handle;

char buf[11] = "0123456789";

/* change the default file mode from text to binary */

_fmode = O_BINARY;

/* create a binary file for reading and writing */

handle = creat("DUMMY.FIL", S_IREAD | S_IWRITE);

/* write 10 bytes to the file */

write(handle, buf, strlen(buf));

/* close the file */

close(handle);

return 0;

}

函数名: creatnew

功能: 创建一个新文件

用法: int creatnew(const char *filename, int attrib);

程序例:

#include ;

int main(void)

{

int handle;

char buf[11] = "0123456789";

/* attempt to create a file that doesn't already exist */

handle = creatnew("DUMMY.FIL", 0);

if (handle == -1)

printf("DUMMY.FIL already exists.\n");

else

{

printf("DUMMY.FIL successfully created.\n");

write(handle, buf, strlen(buf));

close(handle);

}

return 0;

}

函数名: creattemp

功能: 创建一个新文件或重写一个已存在的文件

用法: int creattemp(const char *filename, int attrib);

程序例:

#include ;

int main(void)

{

int handle;

char pathname[128];

strcpy(pathname, "\\");

/* create a unique file in the root directory */

handle = creattemp(pathname, 0);

printf("%s was the unique file created.\n", pathname);

close(handle);

return 0;

}

函数名: cscanf

功能: 从控制台执行格式化输入

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

程序例:

#include ;

int main(void)

{

char string[80];

/* clear the screen */

clrscr();

/* Prompt the user for input */

cprintf("Enter a string with no spaces:");

/* read the input */

cscanf("%s", string);

/* display what was read */

cprintf("\r\nThe string entered is: %s", string);

return 0;

}

函数名: ctime

功能: 把日期和时间转换为字符串

用法: char *ctime(const time_t *time);

程序例:

#include ;

int main(void)

{

time_t t;

time(&t);

printf("Today's date and time: %s\n", ctime(&t));

return 0;

}

函数名: ctrlbrk

功能: 设置Ctrl-Break处理程序

用法: void ctrlbrk(*fptr)(void);

程序例:

#include ;

#define ABORT 0

int c_break(void)

{

printf("Control-Break pressed. Program aborting ...\n");

return (ABORT);

}

int main(void)

{

ctrlbrk(c_break);

for(;;)

{

printf("Looping... Press ; to quit:\n");

}

return 0;

}

函数名: delay

功能: 将程序的执行暂停一段时间(毫秒)

用法: void delay(unsigned milliseconds);

程序例:

/* Emits a 440-Hz tone for 500 milliseconds */

#include ;

int main(void)

{

sound(440);

delay(500);

nosound();

return 0;

}

函数名: delline

功能: 在文本窗口中删去一行

用法: void delline(void);

程序例:

#include ;

int main(void)

{

clrscr();

cprintf("The function DELLINE deletes \

the line containing the\r\n");

cprintf("cursor and moves all lines \

below it one line up.\r\n");

cprintf("DELLINE operates within the \

currently active text\r\n");

cprintf("window. Press any key to \

continue . . .");

gotoxy(1,2); /* Move the cursor to the

second line and first column */

getch();

delline();

getch();

return 0;

}

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Linux C语言常用函数 02 | C#面试题

2012-08-29 09:53
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