CONFSTR(3) | Library Functions Manual | 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 IEEE Std 1003.1-2008 (“POSIX.1”).

`_CS_V6_ENV`
  Return a space separated list of environment variable assignments (other than `PATH`) necessary for obtaining a shell environment compliant with IEEE Std 1003.1-2001 (“POSIX.1”).

`_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 IEEE Std 1003.1-2008 (“POSIX.1”).

# HISTORY

The `confstr` function first appeared in 4.4BSD.

January 21, 2014 | Debian