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'\" t
.\" Copyright, the authors of the Linux man-pages project
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH fabs 3 2025-05-17 "Linux man-pages (unreleased)"
.SH NAME
fabs, fabsf, fabsl \- absolute value of floating-point number
.SH LIBRARY
Math library
.RI ( libm ,\~ \-lm )
.SH SYNOPSIS
.nf
.B #include <math.h>
.P
.BI "double fabs(double " x );
.BI "float fabsf(float " x );
.BI "long double fabsl(long double " x );
.fi
.P
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.P
.BR fabsf (),
.BR fabsl ():
.nf
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
.fi
.SH DESCRIPTION
These functions return the absolute value of the floating-point
number
.IR x .
.SH RETURN VALUE
These functions return the absolute value of
.IR x .
.P
If
.I x
is a NaN, a NaN is returned.
.P
If
.I x
is \-0, +0 is returned.
.P
If
.I x
is negative infinity or positive infinity, positive infinity is returned.
.SH ERRORS
No errors occur.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lbx lb lb
l l l.
Interface Attribute Value
T{
.na
.nh
.BR fabs (),
.BR fabsf (),
.BR fabsl ()
T} Thread safety MT-Safe
.TE
.SH STANDARDS
C11, POSIX.1-2008.
.SH HISTORY
C99, POSIX.1-2001.
.P
The variant returning
.I double
also conforms to
SVr4, 4.3BSD, C89.
.SH SEE ALSO
.BR abs (3),
.BR cabs (3),
.BR ceil (3),
.BR floor (3),
.BR labs (3),
.BR rint (3)
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