数学建模社区-数学中国

标题: 函数大全(u开头) [打印本页]

作者: 韩冰 时间: 2004-10-4 02:54
标题: 函数大全(u开头)
<

>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;
}

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