可爱的消防图片:memcmp.memset.sprintf 的用法 和 意思
memcmp
Compare characters in two buffers.
比较两块内存中的字符
memset
Sets buffers to a specified character
将内存块设置为指定的字符
sprintf
Write formatted data to a string
将格式化的数据写到字符串
memcmp
Compare characters in two buffers.
int memcmp( const void *buf1, const void *buf2, size_t count );
Routine Required Header Compatibility
memcmp <memory.h> or <string.h> ANSI, Win 95, Win NT
For additional compatibility information, see Compatibility in the Introduction.
Libraries
LIBC.LIB Single thread static library, retail version
LIBCMT.LIB Multithread static library, retail version
MSVCRT.LIB Import library for MSVCRT.DLL, retail version
Return Value
The return value indicates the relationship between the buffers.
Return Value Relationship of First count Bytes of buf1 and buf2
< 0 buf1 less than buf2
0 buf1 identical to buf2
> 0 buf1 greater than buf2
Parameters
buf1
First buffer
buf2
Second buffer
count
Number of characters
Remarks
The memcmp function compares the first count bytes of buf1 and buf2 and returns a value indicating their relationship.
Example
/* MEMCMP.C: This program uses memcmp to compare
* the strings named first and second. If the first
* 19 bytes of the strings are equal, the program
* considers the strings to be equal.
*/
#include <string.h>
#include <stdio.h>
void main( void )
{
char first[] = "12345678901234567890";
char second[] = "12345678901234567891";
int result;
printf( "Compare '%.19s' to '%.19s':\n", first, second );
result = memcmp( first, second, 19 );
if( result < 0 )
printf( "First is less than second.\n" );
else if( result == 0 )
printf( "First is equal to second.\n" );
else if( result > 0 )
printf( "First is greater than second.\n" );
printf( "Compare '%.20s' to '%.20s':\n", first, second );
result = memcmp( first, second, 20 );
if( result < 0 )
printf( "First is less than second.\n" );
else if( result == 0 )
printf( "First is equal to second.\n" );
else if( result > 0 )
printf( "First is greater than second.\n" );
}
Output
Compare '1234567890123456789' to '1234567890123456789':
First is equal to second.
Compare '12345678901234567890' to '12345678901234567891':
First is less than second.
Buffer Manipulation Routines
See Also _memccpy, memchr, memcpy, memset, strcmp, strncmp
memset
Sets buffers to a specified character.
void *memset( void *dest, int c, size_t count );
Routine Required Header Compatibility
memset <memory.h> or <string.h> ANSI, Win 95, Win NT
For additional compatibility information, see Compatibility in the Introduction.
Libraries
LIBC.LIB Single thread static library, retail version
LIBCMT.LIB Multithread static library, retail version
MSVCRT.LIB Import library for MSVCRT.DLL, retail version
Return Value
memset returns the value of dest.
Parameters
dest
Pointer to destination
c
Character to set
count
Number of characters
Remarks
The memset function sets the first count bytes of dest to the character c.
Example
/* MEMSET.C: This program uses memset to
* set the first four bytes of buffer to "*".
*/
#include <memory.h>
#include <stdio.h>
void main( void )
{
char buffer[] = "This is a test of the memset function";
printf( "Before: %s\n", buffer );
memset( buffer, '*', 4 );
printf( "After: %s\n", buffer );
}
Output
Before: This is a test of the memset function
After: **** is a test of the memset function
Buffer Manipulation Routines
See Also _memccpy, memchr, memcmp, memcpy, _strnset
sprintf, swprintf
Write formatted data to a string.
int sprintf( char *buffer, const char *format [, argument] ... );
int swprintf( wchar_t *buffer, const wchar_t *format [, argument] ... );
Routine Required Header Compatibility
sprintf <stdio.h> ANSI, Win 95, Win NT
swprintf <stdio.h> or <wchar.h> ANSI, Win 95, Win NT
For additional compatibility information, see Compatibility in the Introduction.
Libraries
LIBC.LIB Single thread static library, retail version
LIBCMT.LIB Multithread static library, retail version
MSVCRT.LIB Import library for MSVCRT.DLL, retail version
Return Value
sprintf returns the number of bytes stored in buffer, not counting the terminating null character. swprintf returns the number of wide characters stored in buffer, not counting the terminating null wide character.
Parameters
buffer
Storage location for output
format
Format-control string
argument
Optional arguments
For more information, see Format Specifications.
Remarks
The sprintf function formats and stores a series of characters and values in buffer. Each argument (if any) is converted and output according to the corresponding format specification in format. The format consists of ordinary characters and has the same form and function as the format argument for printf. A null character is appended after the last character written. If copying occurs between strings that overlap, the behavior is undefined.
swprintf is a wide-character version of sprintf; the pointer arguments to swprintf are wide-character strings. Detection of encoding errors in swprintf may differ from that in sprintf. swprintf and fwprintf behave identically except that swprintf writes output to a string rather than to a destination of type FILE.
Generic-Text Routine Mappings
TCHAR.H Routine _UNICODE & _MBCS Not Defined _MBCS Defined _UNICODE Defined
_stprintf sprintf sprintf swprintf
Example
/* SPRINTF.C: This program uses sprintf to format various
* data and place them in the string named buffer.
*/
#include <stdio.h>
void main( void )
{
char buffer[200], s[] = "computer", c = 'l';
int i = 35, j;
float fp = 1.7320534f;
/* Format and print various data: */
j = sprintf( buffer, "\tString: %s\n", s );
j += sprintf( buffer + j, "\tCharacter: %c\n", c );
j += sprintf( buffer + j, "\tInteger: %d\n", i );
j += sprintf( buffer + j, "\tReal: %f\n", fp );
printf( "Output:\n%s\ncharacter count = %d\n", buffer, j );
}
Output
Output:
String: computer
Character: l
Integer: 35
Real: 1.732053
character count = 71
Stream I/O Routines
See Also _snprintf, fprintf, printf, scanf, sscanf, vprintf Functions