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confstr(3) [freebsd man page]

CONFSTR(3)						   BSD Library Functions Manual 						CONFSTR(3)

confstr -- get string-valued configurable variables LIBRARY
Standard C Library (libc, -lc) SYNOPSIS
#include <unistd.h> size_t confstr(int name, char *buf, size_t len); DESCRIPTION
This interface is specified by IEEE Std 1003.1-2001 (``POSIX.1''). 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_PATH Return a value for the PATH environment 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 config- uration 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. SEE ALSO
getconf(1), pathconf(2), sysconf(3), sysctl(3) HISTORY
The confstr() function first appeared in 4.4BSD. BSD
December 3, 2006 BSD

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CONFSTR(3)                                                   Linux Programmer's Manual                                                  CONFSTR(3)

confstr - get configuration dependent string variables SYNOPSIS
#include <unistd.h> size_t confstr(int name, char *buf, size_t len); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): confstr(): _POSIX_C_SOURCE >= 2 || _XOPEN_SOURCE DESCRIPTION
confstr() gets the value of configuration-dependent string variables. The name argument is the system variable to be queried. The following variables are supported: _CS_GNU_LIBC_VERSION (GNU C library only; since glibc 2.3.2) A string which identifies the GNU C library version on this system (e.g., "glibc 2.3.4"). _CS_GNU_LIBPTHREAD_VERSION (GNU C library only; since glibc 2.3.2) A string which identifies the POSIX implementation supplied by this C library (e.g., "NPTL 2.3.4" or "linuxthreads-0.10"). _CS_PATH A value for the PATH variable which indicates where all the POSIX.2 standard utilities can be found. If buf is not NULL and len is not zero, confstr() copies the value of the string to buf truncated to len - 1 bytes if necessary, with a null byte ('') as terminator. This can be detected by comparing the return value of confstr() against len. If len is zero and buf is NULL, confstr() just returns the value as defined below. RETURN VALUE
If name is a valid configuration variable, confstr() returns the number of bytes (including the terminating null byte) that would be required to hold the entire value of that variable. This value may be greater than len, which means that the value in buf is truncated. If name is a valid configuration variable, but that variable does not have a value, then confstr() returns 0. If name does not correspond to a valid configuration variable, confstr() returns 0, and errno is set to EINVAL. ERRORS
EINVAL The value of name is invalid. ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7). +----------+---------------+---------+ |Interface | Attribute | Value | +----------+---------------+---------+ |confstr() | Thread safety | MT-Safe | +----------+---------------+---------+ CONFORMING TO
POSIX.1-2001, POSIX.1-2008. EXAMPLE
The following code fragment determines the path where to find the POSIX.2 system utilities: char *pathbuf; size_t n; n = confstr(_CS_PATH, NULL, (size_t) 0); pathbuf = malloc(n); if (pathbuf == NULL) abort(); confstr(_CS_PATH, pathbuf, n); SEE ALSO
getconf(1), sh(1), exec(3), fpathconf(3), pathconf(3), sysconf(3), system(3) COLOPHON
This page is part of release 4.15 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at GNU 2017-09-15 CONFSTR(3)
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