CONFSTR(3) FreeBSD Library Functions Manual CONFSTR(3)


confstrget string-valued configurable variables


Standard C Library (libc, -lc)


#include < unistd.h>

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


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

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) 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:

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.


The confstr() function first appeared in 4.4BSD.
December 3, 2006 FreeBSD