c语言函数大全

墙角野猫

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
", i, getchar());
return 0;
}

墙角野猫

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("
i = %d, next char in buffer = %c
", i, getch());
return 0;
}

墙角野猫

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
", 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
",
dt.da_day, month[dt.da_mon], dt.da_year);
return 0;
}

墙角野猫

函数名: unlink
功 能: 删掉一个文件
用 法: int unlink(char *filename);
程序例:
#include
#include
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
");
else
printf("File doesn't exist
");
fclose(fp);
unlink("junk.jnk");
status = access("junk.jnk",0);
if (status == 0)
printf("File exists
");
else
printf("File doesn't exist
");

return 0;
}

墙角野猫

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
#include
#include
#include
#include
#include
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
");
exit(1);
}
length = filelength(handle);
status = lock(handle,0L,length/2);
if (status == 0)
printf("lock succeeded
");
else
printf("lock failed
");
status = unlock(handle,0L,length/2);
if (status == 0)
printf("unlock succeeded
");
else
printf("unlock failed
");
close(handle);
return 0;
}

墙角野猫

函数名: vfprintf
功 能: 送格式化输出到一流中
用 法: int vfprintf(FILE *stream, char *format, va_list param);
程序例:
#include
#include
#include
FILE *fp;
int vfpf(char *fmt, ...)
{
va_list argptr;
int cnt;
va_start(argptr, fmt);
cnt = vfprintf(fp, fmt, argptr);
va_end(argptr);
return(cnt);
}
int main(void)
{
int inumber = 30;
float fnumber = 90.0;
char string[4] = "abc";
fp = tmpfile();
if (fp == NULL)
{
perror("tmpfile() call");
exit(1);
}
vfpf("%d %f %s", inumber, fnumber, string);
rewind(fp);
fscanf(fp,"%d %f %s", &inumber, &fnumber, string);
printf("%d %f %s
", inumber, fnumber, string);
fclose(fp);
return 0;
}

墙角野猫

函数名: vfscanf
功 能: 从流中执行格式化输入
用 法: int vfscanf(FILE *stream, char *format, va_list param);
程序例:
#include
#include
#include
FILE *fp;
int vfsf(char *fmt, ...)
{
va_list argptr;
int cnt;
va_start(argptr, fmt);
cnt = vfscanf(fp, fmt, argptr);
va_end(argptr);
return(cnt);
}
int main(void)
{
int inumber = 30;
float fnumber = 90.0;
char string[4] = "abc";
fp = tmpfile();
if (fp == NULL)
{
perror("tmpfile() call");
exit(1);
}
fprintf(fp,"%d %f %s
",inumber,fnumber,string);
rewind(fp);
vfsf("%d %f %s",&inumber,&fnumber,string);
printf("%d %f %s
",inumber,fnumber,string);
fclose(fp);
return 0;
}

墙角野猫

函数名: vprintf
功 能: 送格式化输出到stdout中
用 法: int vprintf(char *format, va_list param);
程序例:
#include
#include
int vpf(char *fmt, ...)
{
va_list argptr;
int cnt;
va_start(argptr, format);
cnt = vprintf(fmt, argptr);
va_end(argptr);
return(cnt);
}
int main(void)
{
int inumber = 30;
float fnumber = 90.0;
char *string = "abc";
vpf("%d %f %s
",inumber,fnumber,string);
return 0;
}

墙角野猫

函数名: vscanf
功 能: 从stdin中执行格式化输入
用 法: int vscanf(char *format, va_list param);
程序例:
#include
#include
#include
int vscnf(char *fmt, ...)
{
va_list argptr;
int cnt;
printf("Enter an integer, a float, and a string (e.g. i,f,s,)
");
va_start(argptr, fmt);
cnt = vscanf(fmt, argptr);
va_end(argptr);
return(cnt);
}
int main(void)
{
int inumber;
float fnumber;
char string[80];
vscnf("%d, %f, %s", &inumber, &fnumber, string);
printf("%d %f %s
", inumber, fnumber, string);
return 0;
}

墙角野猫

函数名: vsprintf
功 能: 送格式化输出到串中
用 法: int vsprintf(char *string, char *format, va_list param);
程序例:
#include
#include
#include
char buffer[80];
int vspf(char *fmt, ...)
{
va_list argptr;
int cnt;
va_start(argptr, fmt);
cnt = vsprintf(buffer, fmt, argptr);
va_end(argptr);
return(cnt);
}
int main(void)
{
int inumber = 30;
float fnumber = 90.0;
char string[4] = "abc";
vspf("%d %f %s", inumber, fnumber, string);
printf("%s
", buffer);
return 0;
}