confstr - Determine the current value of a specified system
variable defined by a string value
#include <unistd.h>
size_t confstr(
int name,
char *buf,
size_t len );
Standard C Library (libc)
Interfaces documented on this reference page conform to
industry standards as follows:
confstr(): XPG4, XPG4-UNIX
Refer to the standards(5) reference page for more information
about industry standards and associated tags.
Specifies the system variable setting to be returned.
Valid values for the name parameter are defined in the
unistd.h header file: Copies a value for the PATH environment
variable that finds all standard utilities into the
buffer. [Tru64 UNIX] Copies the official name of the
installed operating system product into the buffer.
[Tru64 UNIX] Copies the official system banner into the
buffer. The banner typically consists of the vendor name
followed by the product name. [Tru64 UNIX] Copies the
product version information into the buffer. [Tru64
UNIX] Copies the official abbreviated company name of
the operating system manufacturer into the buffer. If the
abbreviated name was not specified, copies the full company
name (same as _CS_VENDOR_NAME). [Tru64 UNIX] Copies
the official company name of the operating system manufacturer
into the buffer. Specifies values to be passed to
utilities used in building an application. The name of the
parameter establishes type-size constraints for the environment
in which an application is being built: The int,
long, pointer, and off_t types are treated as 32-bit
types. The int, long, and pointer types are treated as
32-bit types, and the off_t type is treated as a type with
at least 64 bits. The int type is treated as a 32-bit
type, and the long, pointer, and off_t types are treated
as 64-bit types. The int type is treated as a type with
at least 32 bits, and the long, pointer, and off_t types
are treated as types with at least 64 bits.
The parameter suffix (id) identifies the component
affected by the type-size constraint: The value of
the parameter is the set of initial options (compilation
options) to be given to cc or c89. The
value of the parameter is the set of final options
(loader options) to be given to cc or c89. The
value of the parameter is the set of libraries to
be given to cc or c89. The value of the parameter
is the set of checking options to be given to lint.
In all cases, if
sysconf (_SC_XBS5_ILP32_OFFBIG)
returns -1, the meaning of the passed values is
unspecified. Points to the buffer into which the
confstr() function copies the name value. Specifies
the size of the buffer storing the name value.
The confstr() function allows an application to determine
the current setting of certain system parameters, limits,
or options that are defined by a string value. The function
is mainly used by applications to find the system
default value for the PATH environment variable.
If the following conditions are true, then the confstr()
function copies that value into a len-byte buffer pointed
to by the buf parameter: The len parameter is not 0 (zero)
The name parameter has a system-defined value The buf
parameter is not a null pointer
If the string to be returned is longer than len bytes,
including the terminating null, then the confstr() function
truncates the string to len-1 bytes and adds a terminating
null to the result. The application can detect that
the string was truncated by comparing the value returned
by confstr() with the value of len.
If the value of the len parameter is set to 0 (zero) or
the buf value is NULL, the confstr() function returns the
size of the buffer needed to hold the entire systemdefined
value, but does not copy the string value.
If the value specified by the name parameter is systemdefined,
the confstr() function returns the size of the
buffer needed to hold the entire value. If this return
value is greater than the specified len value, the string
returned as the buf value is truncated.
If the specified name value is invalid, a value of 0
(zero) is returned, and the errno global variable is set
to indicate the error.
If the specified name value does not have a system-defined
value, the confstr() function returns a value of 0 (zero)
and leaves errno unchanged.
The confstr() function sets errno as follows:
The value of the name parameter is invalid.
To find out how big a buffer is needed to store the
_CS_PATH string value, enter: confstr(_CS_PATH,
NULL, (size_t) 0)
The confstr() function returns the size of the buffer necessary.
Contains system-defined limits. Contains system-defined
environment variables.
Functions: pathconf(2), sysconf(3)
Standards: standards(5)
confstr(3)
[ Back ] | 