---
name: "getenv"
section: "9"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd"]
url: "https://new.carta.tech/freeenv"
---

# getenv(9)

kernel environment variable functions

Part of [freeenv(9)](/freeenv/9.md).

## NAME

**freeenv**, **kern\_getenv**, **getenv\_int**, **getenv\_long**, **getenv\_string**, **getenv\_quad**, **getenv\_uint**, **getenv\_ulong**, **getenv\_bool**, **getenv\_is\_true**, **getenv\_is\_false**, **kern\_setenv**, **testenv**, **kern\_unsetenv** – kernel environment variable functions

## SYNOPSIS

**#include \<sys/param.h\>**

**#include \<sys/systm.h\>**

*void*\

**freeenv**(*char \*env*);

*char* *\**\

**kern\_getenv**(*const char \*name*);

*int*\

**getenv\_int**(*const char \*name*, *int \*data*);

*int*\

**getenv\_long**(*const char \*name*, *long \*data*);

*int*\

**getenv\_string**(*const char \*name*, *char \*data*, *int size*);

*int*\

**getenv\_quad**(*const char \*name*, *quad\_t \*data*);

*int*\

**getenv\_uint**(*const char \*name*, *unsigned int \*data*);

*int*\

**getenv\_ulong**(*const char \*name*, *unsigned long \*data*);

*int*\

**getenv\_bool**(*const char \*name*, *bool \*data*);

*bool*\

**getenv\_is\_true**(*const char \*name*);

*bool*\

**getenv\_is\_false**(*const char \*name*);

*int*\

**kern\_setenv**(*const char \*name*, *const char \*value*);

*int*\

**testenv**(*const char \*name*);

*int*\

**kern\_unsetenv**(*const char \*name*);

## DESCRIPTION

These functions set, unset, fetch, and parse variables from the kernel's environment.

The **kern\_getenv**() function obtains the current value of the kernel environment variable *name* and returns a pointer to the string value. The caller should not modify the string pointed to by the return value. The **kern\_getenv**() function may allocate temporary storage, so the **freeenv**() function must be called to release any allocated resources when the value returned by **kern\_getenv**() is no longer needed.

The **freeenv**() function is used to release the resources allocated by a previous call to **kern\_getenv**(). The *env* argument passed to **freeenv**() is the pointer returned by the earlier call to **kern\_getenv**(). Like [free(3)](/free/3.md), the *env* argument can be *NULL*, in which case no action occurs.

The **kern\_setenv**() function inserts or resets the kernel environment variable *name* to *value*. If the variable *name* already exists, its value is replaced. This function can fail if an internal limit on the number of environment variables is exceeded.

The **kern\_unsetenv**() function deletes the kernel environment variable *name*.

The **testenv**() function is used to determine if a kernel environment variable exists. It returns a non-zero value if the variable *name* exists and zero if it does not.

The **getenv\_int**(), **getenv\_long**(), **getenv\_quad**(), **getenv\_uint**(), and **getenv\_ulong**() functions look for a kernel environment variable *name* and parse it as a signed integer, long integer, signed 64-bit integer, unsigned integer, or an unsigned long integer, respectively. These functions fail and return zero if *name* does not exist or if any invalid characters are present in its value. On success, these function store the parsed value in the integer variable pointed to by *data*. If the parsed value overflows the integer type, a truncated value is stored in *data* and zero is returned. If the value begins with a prefix of “0x” it is interpreted as hexadecimal. If it begins with a prefix of “0” it is interpreted as octal. Otherwise, the value is interpreted as decimal. The value may contain a single character suffix specifying a unit for the value. The interpreted value is multiplied by the unit's magnitude before being returned. The following unit suffixes are supported:

| | |
| --- | --- |
| **Unit** | **Magnitude** |
| k | 2^10 |
| m | 2^20 |
| g | 2^30 |
| t | 2^40 |

The **getenv\_string**() function stores a copy of the kernel environment variable *name* in the buffer described by *data* and *size*. If the variable does not exist, zero is returned. If the variable exists, up to *size*, *-*, *1* characters of its value are copied to the buffer pointed to by *data* followed by a null character and a non-zero value is returned.

The **getenv\_bool**() function interprets the value of the kernel environment variable *name* as a boolean value by performing a case-insensitive comparison against the strings "1", "0", "true", and "false". If the environment variable exists and has a valid boolean value, then that value will be copied to the variable pointed to by *data*. If the environment variable exists but is not a boolean value, then a warning will be printed to the kernel message buffer. The **getenv\_is\_true**() and **getenv\_is\_false**() functions are wrappers around **getenv\_bool**() that simplify testing for a desired boolean value.

## RETURN VALUES

The **kern\_getenv**() function returns a pointer to an environment variable's value on success or NULL if the variable does not exist.

The **kern\_setenv**() and **kern\_unsetenv**() functions return zero on success and -1 on failure.

The **testenv**() function returns zero if the specified environment variable does not exist and a non-zero value if it does exist.

The **getenv\_int**(), **getenv\_long**(), **getenv\_string**(), **getenv\_quad**(), **getenv\_uint**(), **getenv\_ulong**(), and **getenv\_bool**() functions return a non-zero value on success and zero on failure.

The **getenv\_is\_true**() and **getenv\_is\_false**() functions return true if the specified environment variable exists and its value matches the desired boolean condition, and false otherwise.