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;?
}?
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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;?
}?
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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;?
}?
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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;?
}?
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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;?
}?
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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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