CONFSTR(3)

NAME
confstr - get string-valued configurable variables

SYNOPSIS
#include <unistd.h>
size_t
confstr(int name, char *buf, size_t len);

DESCRIPTION
The confstr() function provides a method for applications to get configuration defined string values.

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 NUL terminated.

The available values are as follows:
_CS_PATH
    Return a value for the PATH environment variable that finds all the standard utilities.

_CS_V7_ENV
    Return a space separated list of environment variable assignments (other than PATH) necessary for obtaining a shell environment compliant with p1003.1-2008.

_CS_V6_ENV
    Return a space separated list of environment variable assignments (other than PATH) necessary for obtaining a shell environment compliant with p1003.1-2001.

_CS_POSIX_V7_THREADS_CFLAGS
    Return the compiler flags for compiling objects in a program that uses multiple threads.

_CS_POSIX_V7_THREADS_LDFLAGS
    Return the linker flags for linking an executable that uses multiple threads.

_CS_POSIX_V7_WIDTH_RESTRICTED_ENVS
_CS_POSIX_V6_WIDTH_RESTRICTED_ENVS
    Return a newline separated list of supported compilation environments in which none of the following types are wider than type long: blksize_t, cc_t, mode_t, nfds_t, pid_t, ptrdiff_t, size_t, speed_t, ssize_t, suseconds_t, tcflag_t, wchar_t, and wint_t.

_CS_POSIX_V7_ILP32_OFFBIG_CFLAGS
_CS_POSIX_V7_ILP32_OFFBIG_LDFLAGS
_CS_POSIX_V7_ILP32_OFFBIG_LIBS
_CS_POSIX_V6_ILP32_OFFBIG_CFLAGS
_CS_POSIX_V6_ILP32_OFFBIG_LDFLAGS
_CS_POSIX_V6_ILP32_OFFBIG_LIBS
    If sysconf(_SC_V7_ILP32_OFFBIG) returns a value greater than zero, return the compiler flags for compiling objects, the linker flags for linking an executable, or the linker arguments for additional libraries, respectively, for a compilation environment with 32-bit int, long, and pointer types and an off_t type that has a width of at least 64 bits. Otherwise, the result is unspecified.

_CS_POSIX_V7_LP64_OFF64_CFLAGS
_CS_POSIX_V7_LP64_OFF64_LDFLAGS
_CS_POSIX_V7_LP64_OFF64_LIBS
_CS_POSIX_V6_LP64_OFF64_CFLAGS
_CS_POSIX_V6_LP64_OFF64_LDFLAGS
_CS_POSIX_V6_LP64_OFF64_LIBS
    If sysconf(_SC_V7_LP64_OFF64) returns a value greater than zero, return the compiler flags for compiling objects, the linker flags for linking an executable, or the linker arguments for additional libraries, respectively, for a compilation environment with 64-bit int, long, pointer, and off_t types. Otherwise, the result is unspecified.

_CS_POSIX_V7_LPBIG_OFFBIG_CFLAGS
_CS_POSIX_V7_LPBIG_OFFBIG_LDFLAGS
_CS_POSIX_V7_LPBIG_OFFBIG_LIBS
_CS_POSIX_V6_LPBIG_OFFBIG_CFLAGS
_CS_POSIX_V6_LPBIG_OFFBIG_LDFLAGS
_CS_POSIX_V6_LPBIG_OFFBIG_LIBS
    If sysconf(_SC_V7_LPBIG_OFFBIG) returns a value greater than zero, return the compiler flags for compiling objects, the linker flags for linking an executable, or the linker arguments for additional libraries, respectively, for a compilation environment with int, long, pointer, and off_t types that all have widths of at least 64 bits. Otherwise, the result is unspecified.

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 will fail if:

[EINVAL]
    The value of the name argument is invalid.

SEE ALSO
pathconf(2), sysconf(3)

STANDARDS
The confstr function conforms to p1003.1-2008.

HISTORY
The confstr function first appeared in 4.4BSD.