---
name: "ecvt"
section: "3"
platform: "macos"
package: "Libc"
version: "1752.120.2"
release: "macOS 26.5"
platforms: ["linux", "macos"]
url: "https://new.carta.tech/ecvt"
---

# ecvt(3)

convert double to ASCII string

## NAME

**ecvt**, **fcvt**, **gcvt** – convert double to ASCII string

## SYNOPSIS

**#include \<stdlib.h\>**

*char* *\**\

**ecvt**(*double value*, *int ndigit*, *int \* restrict decpt*, *int \* restrict sign*);

*char* *\**\

**fcvt**(*double value*, *int ndigit*, *int \* restrict decpt*, *int \* restrict sign*);

*char* *\**\

**gcvt**(*double value*, *int ndigit*, *char \*buf*);

## DESCRIPTION

These functions are provided for compatibility with legacy code. New code should use the [snprintf(3)](/snprintf/3.md) function for improved safety and portability.

The **ecvt**(), **fcvt**() and **gcvt**() functions convert the double precision floating-point number *value* to a NUL-terminated ASCII string.

The **ecvt**() function converts *value* to a NUL-terminated string of exactly *ndigit* digits and returns a pointer to that string. The result is padded with zeroes from left to right as needed. There are no leading zeroes unless *value* itself is 0. The least significant digit is rounded in an implementation-dependent manner. The position of the decimal point relative to the beginning of the string is stored in *decpt*. A negative value indicates that the decimal point is located to the left of the returned digits (this occurs when there is no whole number component to *value*). If *value* is zero, it is unspecified whether the integer pointed to by *decpt* will be 0 or 1. The decimal point itself is not included in the returned string. If the sign of the result is negative, the integer pointed to by *sign* is non-zero; otherwise, it is 0.

If the converted value is out of range or is not representable, the contents of the returned string are unspecified.

The **fcvt**() function is identical to **ecvt**() with the exception that *ndigit* specifies the number of digits after the decimal point (zero-padded as needed).

The **gcvt**() function converts *value* to a NUL-terminated string similar to the %g [printf(3)](/printf/3.md) format specifier and stores the result in *buf*. It produces *ndigit* significant digits similar to the %f [printf(3)](/printf/3.md) format specifier where possible. If *ndigit* does allow sufficient precision, the result is stored in exponential notation similar to the %e [printf(3)](/printf/3.md) format specifier. If *value* is less than zero, *buf* will be prefixed with a minus sign. A decimal point is included in the returned string if *value* is not a whole number. Unlike the **ecvt**() and **fcvt**() functions, *buf* is not zero-padded.

## RETURN VALUES

The **ecvt**(), **fcvt**() and **gcvt**() functions return a NUL-terminated string representation of *value*.

## WARNINGS

The **ecvt**() and **fcvt**() functions return a pointer to internal storage space that will be overwritten by subsequent calls to either function.

The maximum possible precision of the return value is limited by the precision of a double and may not be the same on all architectures.

The [snprintf(3)](/snprintf/3.md) function is preferred over these functions for new code.

## SEE ALSO

[printf(3)](/printf/3.md), [strtod(3)](/strtod/3.md)

## STANDARDS

The **ecvt**(), **fcvt**() and **gcvt**() functions conform to IEEE Std 1003.1-2001 (“POSIX.1”).