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.Dd $Mdocdate: January 21 2014 $
.Dt CONFSTR 3
.Os
.Sh NAME
.Nm confstr
.Nd get string-valued configurable variables
.Sh SYNOPSIS
.In unistd.h
.Ft size_t
.Fn confstr "int name" "char *buf" "size_t len"
.Sh DESCRIPTION
The
.Fn confstr
function provides a method for applications to get configuration
defined string values.
.Pp
The
.Fa name
argument specifies the system variable to be queried.
Symbolic constants for each name value are found in the include file
.In unistd.h .
The
.Fa len
argument specifies the size of the buffer referenced by the
argument
.Fa buf .
If
.Fa len
is non-zero,
.Fa buf
is a non-null pointer, and
.Fa name
has a value; up to
.Fa len
\- 1 bytes of the value are copied into the buffer
.Fa buf .
The copied value is always NUL terminated.
.Pp
The available values are as follows:
.Bl -tag -width "123456" -compact
.It Li _CS_PATH
Return a value for the
.Ev PATH
environment variable that finds all the standard utilities.
.Pp
.It Li _CS_V7_ENV
Return a space separated list of environment variable assignments
(other than
.Ev PATH )
necessary for obtaining a shell environment compliant with
.St -p1003.1-2008 .
.Pp
.It Li _CS_V6_ENV
Return a space separated list of environment variable assignments
(other than
.Ev PATH )
necessary for obtaining a shell environment compliant with
.St -p1003.1-2001 .
.Pp
.It Li _CS_POSIX_V7_THREADS_CFLAGS
Return the compiler flags for compiling objects in a program that
uses multiple threads.
.Pp
.It Li _CS_POSIX_V7_THREADS_LDFLAGS
Return the linker flags for linking an executable that uses multiple
threads.
.Pp
.It Li _CS_POSIX_V7_WIDTH_RESTRICTED_ENVS
.It Li _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
.Vt long :
.Vt blksize_t , cc_t , mode_t , nfds_t , pid_t , ptrdiff_t , size_t ,
.Vt speed_t , ssize_t , suseconds_t , tcflag_t , wchar_t ,
and
.Vt wint_t .
.Pp
.It Li _CS_POSIX_V7_ILP32_OFFBIG_CFLAGS
.It Li _CS_POSIX_V7_ILP32_OFFBIG_LDFLAGS
.It Li _CS_POSIX_V7_ILP32_OFFBIG_LIBS
.It Li _CS_POSIX_V6_ILP32_OFFBIG_CFLAGS
.It Li _CS_POSIX_V6_ILP32_OFFBIG_LDFLAGS
.It Li _CS_POSIX_V6_ILP32_OFFBIG_LIBS
If
.Fn 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
.Vt int , long ,
and
.Vt pointer
types and an
.Vt off_t
type that has a width of at least 64 bits.
Otherwise, the result is unspecified.
.Pp
.It Li _CS_POSIX_V7_LP64_OFF64_CFLAGS
.It Li _CS_POSIX_V7_LP64_OFF64_LDFLAGS
.It Li _CS_POSIX_V7_LP64_OFF64_LIBS
.It Li _CS_POSIX_V6_LP64_OFF64_CFLAGS
.It Li _CS_POSIX_V6_LP64_OFF64_LDFLAGS
.It Li _CS_POSIX_V6_LP64_OFF64_LIBS
If
.Fn 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
.Vt int , long , pointer ,
and
.Vt off_t
types.
Otherwise, the result is unspecified.
.Pp
.It Li _CS_POSIX_V7_LPBIG_OFFBIG_CFLAGS
.It Li _CS_POSIX_V7_LPBIG_OFFBIG_LDFLAGS
.It Li _CS_POSIX_V7_LPBIG_OFFBIG_LIBS
.It Li _CS_POSIX_V6_LPBIG_OFFBIG_CFLAGS
.It Li _CS_POSIX_V6_LPBIG_OFFBIG_LDFLAGS
.It Li _CS_POSIX_V6_LPBIG_OFFBIG_LIBS
If
.Fn 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
.Vt int , long , pointer ,
and
.Vt off_t
types that all have widths of at least 64 bits.
Otherwise, the result is unspecified.
.El
.Sh RETURN VALUES
If the call to
.Nm
is not successful, 0 is returned and
.Va errno
is set appropriately.
Otherwise, if the variable does not have a configuration defined value,
0 is returned and
.Va 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
.Fa len ,
the string in
.Fa buf
was truncated.
.Sh ERRORS
The
.Nm
function will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
The value of the
.Fa name
argument is invalid.
.El
.Sh SEE ALSO
.Xr pathconf 2 ,
.Xr sysconf 3
.Sh STANDARDS
The
.Nm
function conforms to
.St -p1003.1-2008 .
.Sh HISTORY
The
.Nm
function first appeared in
.Bx 4.4 .