CONFSTR(3) Library Functions Manual CONFSTR(3)

confstr — get string-valued configurable variables

Standard C Library (libc, -lc)

#include <unistd.h>

size_t
confstr(int name, char *buf, size_t len);

This interface is specified by POSIX. A more flexible (but non-portable) interface is provided by sysctl(3).

The () function provides a method for applications to get configuration defined string values. Shell programmers needing access to these parameters should use the getconf(1) 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:

Provides the path to a user's folder. The directory will be created if it does not already exist.

This directory is created with access permissions of 0755 and restricted by the umask(2) of the calling process and is not intended to be used for sensitive or temporary file storage, as all users can see files created here. If the user's umask allows it, files created here will be world readable, which could lead to information disclosure.

Provides the path to a user's temporary items directory. The directory will be created it if does not already exist. This directory is created with access permissions of 0700 and restricted by the umask(2) of the calling process and is a good location for temporary files.

By default, files in this location may be cleaned (removed) by the system if they are not accessed in 3 days.

Provides the path to the user's cache directory. The directory will be created if it does not already exist. This directory is created with access permissions of 0700 and restricted by the umask(2) of the calling process and is a good location for user cache data as it will not be automatically cleaned by the system.

Files in this location will be removed during safe boot.

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

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.

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

In addition, the following errors may be reported:

[]
The value of the name argument is invalid.
[]
Insufficient storage space is available.
[]
I/O error communicating with dirhelper(8).

If the call to () is not successful, -1 (rather than 0) is returned and errno is set appropriately.

getconf(1), pathconf(2), sysconf(3), sysctl(3)

The confstr() function first appeared in 4.4BSD.

June 18, 2001 macOS 15.2