语言库函数类字母覆盖

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 = L;

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\", _day, month[_mon], _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\",

_day, month[_mon], _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(\"k\",\"w\");

int status;

fprintf(fp,\"junk\");

status = access(\"k\",0);

if (status == 0)

printf(\"File exists\\n\");

else

printf(\"File doesn\'\'t exist\\n\");

fclose(fp);

unlink(\"k\");

status = access(\"k\",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:\\\\t\",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

但消息曝出半个月后 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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