abs, labs, llabs, imaxabs

Defined in header `<stdlib.h>`
int abs( int n );
long labs( long n );
long long llabs( long long n );		(since C99)
Defined in header `<inttypes.h>`
intmax_t imaxabs( intmax_t n );		(since C99)

Computes the absolute value of an integer number. The behavior is undefined if the result cannot be represented by the return type.

Parameters

integer value

Return value

The absolute value of n (i.e. |n|), if it is representable.

Notes

In 2's complement systems, the absolute value of the most-negative value is out of range, e.g. for 32-bit 2's complement type int, INT_MIN is -2147483648, but the would-be result 2147483648 is greater than INT_MAX, which is 2147483647.

Example

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
 
int main(void)
{
    printf("abs(+3) = %d\n", abs(+3));
    printf("abs(-3) = %d\n", abs(-3));
 
//  printf("%+d\n", abs(INT_MIN)); // undefined behavior on 2's complement systems
}

Output:

abs(+3) = 3
abs(-3) = 3

References

C17 standard (ISO/IEC 9899:2018):

7.8.2.1 The imaxabs function (p: 159)
7.22.6.1 The abs, labs and llabs functions (p: 259)

C11 standard (ISO/IEC 9899:2011):

7.8.2.1 The imaxabs function (p: 218)
7.22.6.1 The abs, labs and llabs functions (p: 356)

C99 standard (ISO/IEC 9899:1999):

7.8.2.1 The imaxabs function (p: 199-200)
7.20.6.1 The abs, labs and llabs functions (p: 320)

C89/C90 standard (ISO/IEC 9899:1990):

4.10.6.1 The abs function
4.10.6.3 The labs function