memcmp
From cppreference.com
Defined in header <string.h>
|
||
int memcmp(
const
void
* lhs, const
void
* rhs, size_t count )
;
|
||
Compares the first count bytes of the objects pointed to by lhs and rhs
The sign of the result is the sign of the difference between the values of the first pair of bytes (both interpreted as unsigned char
The behavior is undefined if access occurs beyond the end of either object pointed to by lhs and rhs. The behavior is undefined if either lhs or rhs
Parameters
lhs, rhs | - | pointers to the objects to compare |
count | - | number of bytes to examine |
Return value
Negative value if lhs appears before rhs in lexicographical order.
Zero if lhs and rhs compare equal, or if count is zero.
Positive value if lhs appears after rhs in lexicographical order.
Notes
This function reads object representations +0 and -0 or for +0.0 and –0.0
Example
Run this code
#include <stdio.h> #include <string.h> void demo(const char* lhs, const char* rhs, size_t sz) { for(size_t n = 0; n < sz; ++n) putchar(lhs[n]); int rc = memcmp(lhs, rhs, sz); const char *rel = rc < 0 ? " precedes " : rc > 0 ? " follows " : " compares equal "; fputs(rel, stdout); for(size_t n = 0; n < sz; ++n) putchar(rhs[n]); puts(" in lexicographical order"); } int main(void) { char a1[] = {'a','b','c'}; char a2[sizeof a1] = {'a','b','d'}; demo(a1, a2, sizeof a1); demo(a2, a1, sizeof a1); demo(a1, a1, sizeof a1); }
Output:
abc precedes abd in lexicographical order abd follows abc in lexicographical order abc compares equal to abc in lexicographical order
References
- C23 standard (ISO/IEC 9899:2024):
- 7.24.4.1 The memcmp function (p: TBD)
- C17 standard (ISO/IEC 9899:2018):
- 7.24.4.1 The memcmp function (p: 266)
- C11 standard (ISO/IEC 9899:2011):
- 7.24.4.1 The memcmp function (p: 365)
- C99 standard (ISO/IEC 9899:1999):
- 7.21.4.1 The memcmp function (p: 328)
- C89/C90 standard (ISO/IEC 9899:1990):
- 4.11.4.1 The memcmp function
See also
compares two strings (function) |
|
compares a certain amount of characters of two strings (function) |
|
C++ documentation for memcmp
|