---
name: "confstr"
section: "3"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["linux", "freebsd", "macos"]
url: "https://new.carta.tech/confstr"
---

# confstr(3)

get string-valued configurable variables

## NAME

**confstr** – get string-valued configurable variables

## LIBRARY

Standard C Library (libc, -lc)

## SYNOPSIS

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

*size\_t*\

**confstr**(*int name*, *char \*buf*, *size\_t len*);

## DESCRIPTION

This interface is specified by IEEE Std 1003.1-2001 (“POSIX.1”). A more flexible (but non-portable) interface is provided by [sysctl(3)](/sysctl/3.md).

The **confstr**() function provides a method for applications to get configuration defined string values. Shell programmers needing access to these parameters should use the [getconf(1)](/getconf/1.md) utility.

The *name* argument specifies the system variable to be queried. Symbolic constants for each name value are found in the include file ⟨unistd.h⟩. The *len* argument specifies the size of the buffer referenced by the argument *buf*. If *len* is non-zero, *buf* is a non-null pointer, and *name* has a value, up to *len* - 1 bytes of the value are copied into the buffer *buf*. The copied value is always null terminated.

The available values are as follows:

- \_CS\_PATH

  Return a value for the PATH environment variable that finds all the standard utilities.

## RETURN VALUES

If the call to **confstr**() is not successful, 0 is returned and *errno* is set appropriately. Otherwise, if the variable does not have a configuration defined value, 0 is returned and *errno* is not modified. Otherwise, the buffer size needed to hold the entire configuration-defined value is returned. If this size is greater than the argument *len*, the string in *buf* was truncated.

## ERRORS

The **confstr**() function may fail and set *errno* for any of the errors specified for the library functions [malloc(3)](/malloc/3.md) and [sysctl(3)](/sysctl/3.md).

In addition, the following errors may be reported:

- \[EINVAL\]

  The value of the *name* argument is invalid.

## SEE ALSO

[getconf(1)](/getconf/1.md), [pathconf(2)](/pathconf/2.md), [sysconf(3)](/sysconf/3.md), [sysctl(3)](/sysctl/3.md)

## HISTORY

The **confstr**() function first appeared in 4.4BSD.