C语言库函数---unix常用系统调用---使用说明(zt)

kj501

[php]
函数名: tan
功  能: 正切函数
用  法: double tan(double x);
程序例:

#include <stdio.h>
#include <math.h>

int main(void)
{
   double result, x;

   x = 0.5;
   result = tan(x);
   printf("The tan of %lf is %lf\n", x, result);
   return 0;
}
   
   
   

函数名: tanh
功  能: 双曲正切函数
用  法: double tanh(double x);
程序例:

#include <stdio.h>
#include <math.h>

int main(void)
{
   double result, x;

   x = 0.5;
   result = tanh(x);
   printf("The hyperbolic tangent of %lf is %lf\n", x, result);
   return 0;
}
   
   
   
   

函数名: tell
功  能: 取文件指针的当前位置
用  法: long tell(int handle);
程序例:

#include <string.h>
#include <stdio.h>
#include <fcntl.h>
#include <io.h>

int main(void)
{
   int handle;
   char msg[] = "Hello world";

   if ((handle = open("TEST.$$$", O_CREAT | O_TEXT | O_APPEND)) == -1)
   {
      perror("Error:");
      return 1;
   }
   write(handle, msg, strlen(msg));
   printf("The file pointer is at byte %ld\n", tell(handle));
   close(handle);
   return 0;
}
   
   
   
   

函数名: textattr
功  能: 设置文本属性
用  法: void textattr(int attribute);
程序例:

#include <conio.h>

int main(void)
{
   int i;

   clrscr();
   for (i=0; i<9; i++)
   {
       textattr(i + ((i+1) << 4));
       cprintf("This is a test\r\n");
   }

   return 0;
}
   
   
   

函数名: textbackground
功  能: 选择新的文本背景颜色
用  法: void textbackground(int color);
程序例:

#include <conio.h>

int main(void)
{
   int i, j;

   clrscr();
   for (i=0; i<9; i++)
   {
       for (j=0; j<80; j++)
         cprintf("C");
       cprintf("\r\n");
       textcolor(i+1);
       textbackground(i);
   }

   return 0;
}
   
   
   

函数名: textcolor
功  能: 在文本模式中选择新的字符颜色
用  法: void textcolor(int color);
程序例:
#include <conio.h>

int main(void)
{
   int i;

   for (i=0; i<15; i++)
   {
       textcolor(i);
       cprintf("Foreground Color\r\n");
   }

   return 0;
}
   
   
   

函数名: textheight
功  能: 返回以像素为单位的字符串高度
用  法: int far textheight(char far *textstring);
程序例:

#include <graphics.h>
#include <stdlib.h>
#include <stdio.h>
#include <conio.h>

int main(void)
{
   /* request auto detection */
   int gdriver = DETECT, gmode, errorcode;
   int y = 0;
   int i;
   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("ress any key to halt:");
      getch();
      exit(1); /* terminate with an error code */
   }

   /* draw some text on the screen */
   for (i=1; i<11; i++)
   {
      /* select the text style, direction, and size */
      settextstyle(TRIPLEX_FONT, HORIZ_DIR, i);

      /* create a message string */
      sprintf(msg, "Size: %d", i);

      /* output the message */
      outtextxy(1, y, msg);

      /* advance to the next text line */
      y += textheight(msg);
   }

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

函数名: textmode
功  能: 将屏幕设置成文本模式
用  法: void textmode(int mode);
程序例:

#include <conio.h>

int main(void)
{
   textmode(BW40);
   cprintf("ABC");
   getch();

   textmode(C40);
   cprintf("ABC");
   getch();

   textmode(BW80);
   cprintf("ABC");
   getch();

   textmode(C80);
   cprintf("ABC");
   getch();

   textmode(MONO);
   cprintf("ABC");
   getch();

   return 0;
}
   
   

函数名: textwidth
功  能: 返回以像素为单位的字符串宽度
用  法: int far textwidth(char far *textstring);
程序例:

#include <graphics.h>
#include <stdlib.h>
#include <stdio.h>
#include <conio.h>

int main(void)
{
   /* request auto detection */
   int gdriver = DETECT, gmode, errorcode;
   int x = 0, y = 0;
   int i;
   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("ress any key to halt:");
      getch();
      exit(1); /* terminate with an error code */
   }

   y = getmaxy() / 2;

   settextjustify(LEFT_TEXT, CENTER_TEXT);
   for (i=1; i<11; i++)
   {
      /* select the text style, direction, and size */
      settextstyle(TRIPLEX_FONT, HORIZ_DIR, i);

      /* create a message string */
      sprintf(msg, "Size: %d", i);

      /* output the message */
      outtextxy(x, y, msg);

      /* advance to the end of the text */
      x += textwidth(msg);
   }

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

函数名: time
功  能: 取一天的时间
用  法: logn time(long *tloc);
程序例:

#include <time.h>
#include <stdio.h>
#include <dos.h>

int main(void)
{
   time_t t;

   t = time(NULL);
   printf("The number of seconds since January 1, 1970 is %ld",t);
   return 0;
}
   
   
   

函数名: tmpfile
功  能: 以二进制方式打开暂存文件
用  法: FILE *tmpfile(void);
程序例:

#include <stdio.h>
#include <process.h>

int main(void)
{
   FILE *tempfp;

   tempfp = tmpfile();
   if (tempfp)
      printf("Temporary file created\n");
   else
   {
      printf("Unable to create temporary file\n");
      exit(1);
   }

   return 0;
}
   
   
   

函数名: tmpnam
功  能: 创建一个唯一的文件名
用  法: char *tmpnam(char *sptr);
程序例:

#include <stdio.h>

int main(void)
{
   char name[13];

   tmpnam(name);
   printf("Temporary name: %s\n", name);
   return 0;
}
   
   
   

函数名: tolower
功  能: 把字符转换成小写字母
用  法: int tolower(int c);
程序例:

#include <string.h>
#include <stdio.h>
#include <ctype.h>

int main(void)
{
   int length, i;
   char *string = "THIS IS A STRING";

   length = strlen(string);
   for (i=0; i<length; i++)
   {
       string = tolower(string);
   }
   printf("%s\n",string);

   return 0;
}
   
   

函数名: toupper
功  能: 把字符转换成大写字母
用  法: int toupper(int c);
程序例:

#include <string.h>
#include <stdio.h>
#include <ctype.h>

int main(void)
{
   int length, i;
   char *string = "this is a string";

   length = strlen(string);
   for (i=0; i<length; i++)
   {
      string = toupper(string);
   }

   printf("%s\n",string);

   return 0;
}
   
   

函数名: tzset
功  能: UNIX时间兼容函数
用  法: void tzset(void);
程序例:

#include <time.h>
#include <stdlib.h>
#include <stdio.h>

int main(void)
{
   time_t td;

   putenv("TZ=PST8PDT");
   tzset();
   time(&td);
   printf("Current time = %s\n", asctime(localtime(&td)));
   return 0;
}  
[/php]

kj501

[php]
函数名: ultoa
功  能: 转换一个无符号长整型数为字符串
用  法: char *ultoa(unsigned long value, char *string, int radix);
程序例:

#include <stdlib.h>
#include <stdio.h>

int main( void )
{
   unsigned long lnumber = 3123456789L;
   char string[25];

   ultoa(lnumber,string,10);
   printf("string = %s  unsigned long = %lu\n",string,lnumber);

   return 0;
}
   
   
   

函数名: ungetc
功  能: 把一个字符退回到输入流中
用  法: int ungetc(char c, FILE *stream);
程序例:

#include <stdio.h>
#include <ctype.h>

int main( void )
{
   int i=0;
   char ch;

   puts("Input an integer followed by a char:");

   /* read chars until non digit or EOF */
   while((ch = getchar()) != EOF && isdigit(ch))
      i = 10 * i + ch - 48; /* convert ASCII into int value */

   /* if non digit char was read, push it back into input buffer */
   if (ch != EOF)
      ungetc(ch, stdin);

   printf("i = %d, next char in buffer = %c\n", i, getchar());
   return 0;
}
   
   
   

函数名: ungetch
功  能: 把一个字符退回到键盘缓冲区中
用  法: int ungetch(int c);
程序例:

#include <stdio.h>
#include <ctype.h>
#include <conio.h>

int main( void )
{
   int i=0;
   char ch;

   puts("Input an integer followed by a char:");

   /* read chars until non digit or EOF */
   while((ch = getche()) != EOF && isdigit(ch))
      i = 10 * i + ch - 48; /* convert ASCII into int value */

   /* if non digit char was read, push it back into input buffer */
   if (ch != EOF)
      ungetch(ch);

   printf("\n\ni = %d, next char in buffer = %c\n", i, getch());
   return 0;
}
   
   
   

函数名: unixtodos
功  能: 把日期和时间转换成DOS格式
用  法: void unixtodos(long utime, struct date *dateptr,
   struct time *timeptr);
程序例:

#include <stdio.h>
#include <dos.h>

char *month[] = {"---", "Jan", "Feb", "Mar", "Apr", "May", "Jun",
                 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};

#define SECONDS_PER_DAY 86400L  /* the number of seconds in one day */

struct date dt;
struct time tm;

int main(void)
{
   unsigned long val;

/* get today's date and time */
   getdate(&dt);
   gettime(&tm);
   printf("today is %d %s %d\n", dt.da_day, month[dt.da_mon], dt.da_year);

/* convert date and time to unix format (number of seconds since Jan 1, 1970 */
   val = dostounix(&dt, &tm);
/* subtract 42 days worth of seconds */
   val -= (SECONDS_PER_DAY * 42);

/* convert back to dos time and date */
   unixtodos(val, &dt, &tm);
   printf("42 days ago it was %d %s %d\n",
        dt.da_day, month[dt.da_mon], dt.da_year);
   return 0;
}
   
   
   

函数名: unlink
功  能: 删掉一个文件
用  法: int unlink(char *filename);
程序例:

#include <stdio.h>
#include <io.h>

int main(void)
{
   FILE *fp = fopen("junk.jnk","w");
   int status;

   fprintf(fp,"junk");

   status = access("junk.jnk",0);
   if (status == 0)
      printf("File exists\n");
   else
      printf("File doesn't exist\n");

   fclose(fp);
   unlink("junk.jnk");
   status = access("junk.jnk",0);
   if (status == 0)
      printf("File exists\n");
   else
      printf("File doesn't exist\n");
   

   return 0;
}
   
   
   

函数名: unlock
功  能: 解除文件共享锁
用  法: int unlock(int handle, long offset, long length);
程序例:

#include <io.h>
#include <fcntl.h>
#include <sys\stat.h>
#include <process.h>
#include <share.h>
#include <stdio.h>

int main(void)
{
   int handle, status;
   long length;

   handle = sopen("c:\\autoexec.bat",O_RDONLY,SH_DENYNO,S_IREAD);

   if (handle < 0)
   {
       printf("sopen failed\n");
       exit(1);
   }

   length = filelength(handle);
   status = lock(handle,0L,length/2);

   if (status == 0)
      printf("lock succeeded\n");
   else
      printf("lock failed\n");

   status = unlock(handle,0L,length/2);

   if (status == 0)
      printf("unlock succeeded\n");
   else
      printf("unlock failed\n");

   close(handle);
   return 0;
}
[/php]

kj501

[php]
函数名: vfprintf
功  能: 送格式化输出到一流中
用  法: int vfprintf(FILE *stream, char *format, va_list param);
程序例:

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>

FILE *fp;

int vfpf(char *fmt, ...)
{
   va_list argptr;
   int cnt;

   va_start(argptr, fmt);
   cnt = vfprintf(fp, fmt, argptr);
   va_end(argptr);

   return(cnt);
}

int main(void)
{
   int inumber = 30;
   float fnumber = 90.0;
   char string[4] = "abc";

   fp = tmpfile();
   if (fp == NULL)
   {
      perror("tmpfile() call");
      exit(1);
   }

   vfpf("%d %f %s", inumber, fnumber, string);
   rewind(fp);
   fscanf(fp,"%d %f %s", &inumber, &fnumber, string);
   printf("%d %f %s\n", inumber, fnumber, string);
   fclose(fp);

   return 0;
}
   
   
   

函数名: vfscanf
功  能: 从流中执行格式化输入
用  法: int vfscanf(FILE *stream, char *format, va_list param);
程序例:

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>

FILE *fp;

int vfsf(char *fmt, ...)
{
   va_list  argptr;
   int cnt;

   va_start(argptr, fmt);
   cnt = vfscanf(fp, fmt, argptr);
   va_end(argptr);

   return(cnt);
}

int main(void)
{
   int inumber = 30;
   float fnumber = 90.0;
         char string[4] = "abc";

   fp = tmpfile();
   if (fp == NULL)
   {
      perror("tmpfile() call");
      exit(1);
   }
   fprintf(fp,"%d %f %s\n",inumber,fnumber,string);
   rewind(fp);

   vfsf("%d %f %s",&inumber,&fnumber,string);
   printf("%d %f %s\n",inumber,fnumber,string);
   fclose(fp);

   return 0;
}
   
   

函数名: vprintf
功  能: 送格式化输出到stdout中
用  法: int vprintf(char *format, va_list param);
程序例:

#include <stdio.h>
#include <stdarg.h>

int vpf(char *fmt, ...)
{
   va_list argptr;
   int cnt;

   va_start(argptr, format);
   cnt = vprintf(fmt, argptr);
   va_end(argptr);

   return(cnt);
}

int main(void)
{
   int inumber = 30;
   float fnumber = 90.0;
   char *string = "abc";

   vpf("%d %f %s\n",inumber,fnumber,string);

   return 0;
}
   
   

函数名: vscanf
功  能: 从stdin中执行格式化输入
用  法: int vscanf(char *format, va_list param);
程序例:

#include <stdio.h>
#include <conio.h>
#include <stdarg.h>

int vscnf(char *fmt, ...)
{
   va_list argptr;
   int cnt;

   printf("Enter an integer, a float,  and a string (e.g. i,f,s,)\n");
   va_start(argptr, fmt);
   cnt = vscanf(fmt, argptr);
   va_end(argptr);

   return(cnt);
}

int main(void)
{
   int inumber;
   float fnumber;
   char string[80];

   vscnf("%d, %f, %s", &inumber, &fnumber, string);
   printf("%d %f %s\n", inumber, fnumber, string);

   return 0;
}
   
   
   

函数名: vsprintf
功  能: 送格式化输出到串中
用  法: int vsprintf(char *string, char *format, va_list param);
程序例:

#include <stdio.h>
#include <conio.h>
#include <stdarg.h>

char buffer[80];

int vspf(char *fmt, ...)
{
   va_list argptr;
   int cnt;

   va_start(argptr, fmt);
   cnt = vsprintf(buffer, fmt, argptr);
   va_end(argptr);

   return(cnt);
}

int main(void)
{
   int inumber = 30;
   float fnumber = 90.0;
   char string[4] = "abc";

   vspf("%d %f %s", inumber, fnumber, string);
   printf("%s\n", buffer);
   return 0;
}
   
   
   

函数名: vsscanf
功  能: 从流中执行格式化输入
用  法: int vsscanf(char *s, char *format, va_list param);
程序例:

#include <stdio.h>
#include <conio.h>
#include <stdarg.h>

char buffer[80] = "30 90.0 abc";

int vssf(char *fmt, ...)
{
   va_list  argptr;
   int cnt;

   fflush(stdin);

   va_start(argptr, fmt);
   cnt = vsscanf(buffer, fmt, argptr);
   va_end(argptr);

   return(cnt);
}

int main(void)
{
   int inumber;
   float fnumber;
   char string[80];

   vssf("%d %f %s", &inumber, &fnumber, string);
   printf("%d %f %s\n", inumber, fnumber, string);
   return 0;
}  
[/php]

kj501

[php]
函数名: wherex
功  能: 返回窗口内水平光标位置
用  法: int wherex(void);
程序例:

#include <conio.h>

int main(void)
{
   clrscr();
   gotoxy(10,10);
   cprintf("Current location is X: %d  Y: %d\r\n", wherex(), wherey());
   getch();

   return 0;
}


   

函数名: wherey
功  能: 返回窗口内垂直光标位置
用  法: int wherey(void);
程序例:

#include <conio.h>

int main(void)
{
   clrscr();
   gotoxy(10,10);
   cprintf("Current location is X: %d  Y: %d\r\n", wherex(), wherey());
   getch();

   return 0;
}


   

函数名: window
功  能: 定义活动文本模式窗口
用  法: void window(int left, int top, int right, int bottom);
程序例:

#include <conio.h>

int main(void)
{

   window(10,10,40,11);
   textcolor(BLACK);
   textbackground(WHITE);
   cprintf("This is a test\r\n");

   return 0;
}


   

函数名: write
功  能: 写到一文件中
用  法: int write(int handel, void *buf, int nbyte);
程序例:

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys\stat.h>
#include <io.h>
#include <string.h>

int main(void)
{
   int handle;
   char string[40];
   int length, res;

   /*
    Create a file named "TEST.$$$" in the current directory and write
    a string to it.  If "TEST.$$$" already exists, it will be overwritten.
   */

   if ((handle = open("TEST.$$$", O_WRONLY | O_CREAT | O_TRUNC,
                         S_IREAD | S_IWRITE)) == -1)
   {
      printf("Error opening file.\n");
      exit(1);
   }

   strcpy(string, "Hello, world!\n");
   length = strlen(string);

   if ((res = write(handle, string, length)) != length)
   {
      printf("Error writing to the file.\n");
      exit(1);
   }
   printf("Wrote %d bytes to the file.\n", res);

   close(handle);
   return 0;
}
[/php]