📄 王大刚--c语言编程宝典--u.htm
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<P>函数名: ultoa <BR>功 能: 转换一个无符号长整型数为字符串 <BR>用 法: char
*ultoa(unsigned long value, char *string, int radix); <BR>程序例: <BR>
<P>#include <stdlib.h> <BR>#include <stdio.h> <BR>
<P>int main( void ) <BR>{ <BR> unsigned long lnumber =
3123456789L; <BR> char string[25]; <BR>
<P> ultoa(lnumber,string,10); <BR> printf("string
= %s unsigned long = %lu\n",string,lnumber); <BR>
<P> return 0; <BR>} <BR> <BR> <BR> <BR>
<P>函数名: ungetc <BR>功 能: 把一个字符退回到输入流中 <BR>用 法: int ungetc(char
c, FILE *stream); <BR>程序例: <BR>
<P>#include <stdio.h> <BR>#include <ctype.h> <BR>
<P>int main( void ) <BR>{ <BR> int i=0; <BR> char
ch; <BR>
<P> puts("Input an integer followed by a char:"); <BR>
<P> /* read chars until non digit or EOF */ <BR>
while((ch = getchar()) != EOF && isdigit(ch))
<BR> i = 10 * i + ch - 48; /* convert ASCII
into int value */ <BR>
<P> /* if non digit char was read, push it back into input
buffer */ <BR> if (ch != EOF)
<BR> ungetc(ch, stdin); <BR>
<P> printf("i = %d, next char in buffer = %c\n", i,
getchar()); <BR> return 0; <BR>} <BR> <BR>
<BR> <BR>
<P>函数名: ungetch <BR>功 能: 把一个字符退回到键盘缓冲区中 <BR>用 法: int
ungetch(int c); <BR>程序例: <BR>
<P>#include <stdio.h> <BR>#include <ctype.h> <BR>#include
<conio.h> <BR>
<P>int main( void ) <BR>{ <BR> int i=0; <BR> char
ch; <BR>
<P> puts("Input an integer followed by a char:"); <BR>
<P> /* read chars until non digit or EOF */ <BR>
while((ch = getche()) != EOF && isdigit(ch))
<BR> i = 10 * i + ch - 48; /* convert ASCII
into int value */ <BR>
<P> /* if non digit char was read, push it back into input
buffer */ <BR> if (ch != EOF)
<BR> ungetch(ch); <BR>
<P> printf("\n\ni = %d, next char in buffer = %c\n", i,
getch()); <BR> return 0; <BR>} <BR> <BR>
<BR> <BR>
<P>函数名: unixtodos <BR>功 能: 把日期和时间转换成DOS格式 <BR>用 法: void
unixtodos(long utime, struct date *dateptr, <BR> struct time
*timeptr); <BR>程序例: <BR>
<P>#include <stdio.h> <BR>#include <dos.h> <BR>
<P>char *month[] = {"---", "Jan", "Feb", "Mar", "Apr", "May", "Jun",
<BR>
"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"}; <BR>
<P>#define SECONDS_PER_DAY 86400L /* the number of seconds in one
day */ <BR>
<P>struct date dt; <BR>struct time tm; <BR>
<P>int main(void) <BR>{ <BR> unsigned long val; <BR>
<P>/* get today's date and time */ <BR> getdate(&dt);
<BR> gettime(&tm); <BR> printf("today is %d %s
%d\n", dt.da_day, month[dt.da_mon], dt.da_year); <BR>
<P>/* convert date and time to unix format (number of seconds since Jan 1,
1970 */ <BR> val = dostounix(&dt, &tm); <BR>/*
subtract 42 days worth of seconds */ <BR> val -=
(SECONDS_PER_DAY * 42); <BR>
<P>/* convert back to dos time and date */ <BR> unixtodos(val,
&dt, &tm); <BR> printf("42 days ago it was %d %s
%d\n", <BR> dt.da_day,
month[dt.da_mon], dt.da_year); <BR> return 0; <BR>} <BR>
<BR> <BR> <BR>
<P>函数名: unlink <BR>功 能: 删掉一个文件 <BR>用 法: int unlink(char
*filename); <BR>程序例: <BR>
<P>#include <stdio.h> <BR>#include <io.h> <BR>
<P>int main(void) <BR>{ <BR> FILE *fp = fopen("junk.jnk","w");
<BR> int status; <BR>
<P> fprintf(fp,"junk"); <BR>
<P> status = access("junk.jnk",0); <BR> if (status
== 0) <BR> printf("File exists\n");
<BR> else <BR> printf("File
doesn't exist\n"); <BR>
<P> fclose(fp); <BR> unlink("junk.jnk");
<BR> status = access("junk.jnk",0); <BR> if
(status == 0) <BR> printf("File exists\n");
<BR> else <BR> printf("File
doesn't exist\n"); <BR> <BR>
<P> return 0; <BR>} <BR> <BR> <BR> <BR>
<P>函数名: unlock <BR>功 能: 解除文件共享锁 <BR>用 法: int unlock(int
handle, long offset, long length); <BR>程序例: <BR>
<P>#include <io.h> <BR>#include <fcntl.h> <BR>#include
<sys\stat.h> <BR>#include <process.h> <BR>#include
<share.h> <BR>#include <stdio.h> <BR>
<P>int main(void) <BR>{ <BR> int handle, status;
<BR> long length; <BR>
<P> handle =
sopen("c:\\autoexec.bat",O_RDONLY,SH_DENYNO,S_IREAD); <BR>
<P> if (handle < 0) <BR> {
<BR> printf("sopen failed\n");
<BR> exit(1); <BR> } <BR>
<P> length = filelength(handle); <BR> status =
lock(handle,0L,length/2); <BR>
<P> if (status == 0) <BR>
printf("lock succeeded\n"); <BR> else
<BR> printf("lock failed\n"); <BR>
<P> status = unlock(handle,0L,length/2); <BR>
<P> if (status == 0) <BR>
printf("unlock succeeded\n"); <BR> else
<BR> printf("unlock failed\n"); <BR>
<P> close(handle); <BR> return 0; <BR>} <BR>
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