NAME
confstr —
get string-valued configurable
variables
LIBRARY
library “libc”
SYNOPSIS
#include
<unistd.h>
size_t
confstr(int
name, char *buf,
size_t len);
DESCRIPTION
This interface is specified by POSIX. 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:
_CS_DARWIN_USER_DIR- 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.
_CS_DARWIN_USER_TEMP_DIR- 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.
_CS_DARWIN_USER_CACHE_DIR- 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.
_CS_PATH- Return a value for the
PATHenvironment 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) and sysctl(3).
In addition, the following errors may be reported:
- [
EINVAL] - The value of the name argument is invalid.
- [
ENOMEM] - Insufficient storage space is available.
- [
EIO] - I/O error communicating with dirhelper(8).
LEGACY ERRORS
If the call to
confstr()
is not successful, -1 (rather than 0) is returned and
errno is set appropriately.
SEE ALSO
HISTORY
The confstr() function first appeared in
4.4BSD.