C语言函数大全（5）

U：

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;
}

V：

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;
}

W：

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;
}