C语言函数大全(u开头)

文章作者 100test 发表时间 2007:03:10 17:25:26
来源 100Test.Com百考试题网

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
#include
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
#include
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
#include
#include
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
#include
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",