confstr(3) Library Functions Manual confstr(3)
NAME
confstr - Determines the current value of a specified system variable defined by a string value
LIBRARY
Standard C Library (libc)
SYNOPSIS
#include <unistd.h>
size_t confstr( int name, char *buf, size_t len);
STANDARDS
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.
PARAMETERS
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.
DESCRIPTION
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 system-defined value, but does not copy the string value.
EXAMPLES
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.
RETURN VALUES
If the value specified by the name parameter is system-defined, 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.
ERRORS
The confstr() function sets errno as follows:
The value of the name parameter is invalid.
FILES
Contains system-defined limits. Contains system-defined environment variables.
RELATED INFORMATION
Functions: pathconf(2), sysconf(3)
Standards: standards(5) delim off
confstr(3)