1CONFSTR(3)                 Linux Programmer's Manual                CONFSTR(3)
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NAME

6       confstr - get configuration dependent string variables
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SYNOPSIS

9       #include <unistd.h>
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11       size_t confstr(int name, char *buf, size_t len);
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13   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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15       confstr():
16           _POSIX_C_SOURCE >= 2 || _XOPEN_SOURCE
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DESCRIPTION

19       confstr() gets the value of configuration-dependent string variables.
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21       The  name argument is the system variable to be queried.  The following
22       variables are supported:
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24       _CS_GNU_LIBC_VERSION (GNU C library only; since glibc 2.3.2)
25              A string which identifies the GNU C library version on this sys‐
26              tem (e.g., "glibc 2.3.4").
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28       _CS_GNU_LIBPTHREAD_VERSION (GNU C library only; since glibc 2.3.2)
29              A  string  which identifies the POSIX implementation supplied by
30              this C library (e.g., "NPTL 2.3.4" or "linuxthreads-0.10").
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32       _CS_PATH
33              A value for the PATH variable  which  indicates  where  all  the
34              POSIX.2 standard utilities can be found.
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36       If  buf  is not NULL and len is not zero, confstr() copies the value of
37       the string to buf truncated to len - 1 bytes if necessary, with a  null
38       byte  ('\0')  as terminator.  This can be detected by comparing the re‐
39       turn value of confstr() against len.
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41       If len is zero and buf is NULL, confstr() just returns the value as de‐
42       fined below.
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RETURN VALUE

45       If name is a valid configuration variable, confstr() returns the number
46       of bytes (including the terminating null byte) that would  be  required
47       to  hold  the entire value of that variable.  This value may be greater
48       than len, which means that the value in buf is truncated.
49
50       If name is a valid configuration variable, but that variable  does  not
51       have a value, then confstr() returns 0.  If name does not correspond to
52       a valid configuration variable, confstr() returns 0, and errno  is  set
53       to EINVAL.
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ERRORS

56       EINVAL The value of name is invalid.
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ATTRIBUTES

59       For  an  explanation  of  the  terms  used  in  this  section,  see at‐
60       tributes(7).
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62       ┌────────────────────────────────────────────┬───────────────┬─────────┐
63       │Interface                                   │ Attribute     │ Value   │
64       ├────────────────────────────────────────────┼───────────────┼─────────┤
65       │confstr()                                   │ Thread safety │ MT-Safe │
66       └────────────────────────────────────────────┴───────────────┴─────────┘
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CONFORMING TO

69       POSIX.1-2001, POSIX.1-2008.
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EXAMPLES

72       The following code fragment determines  the  path  where  to  find  the
73       POSIX.2 system utilities:
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75           char *pathbuf;
76           size_t n;
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78           n = confstr(_CS_PATH, NULL, (size_t) 0);
79           pathbuf = malloc(n);
80           if (pathbuf == NULL)
81               abort();
82           confstr(_CS_PATH, pathbuf, n);
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SEE ALSO

85       getconf(1), sh(1), exec(3), fpathconf(3), pathconf(3), sysconf(3), sys‐
86       tem(3)
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COLOPHON

89       This page is part of release 5.13 of the Linux  man-pages  project.   A
90       description  of  the project, information about reporting bugs, and the
91       latest    version    of    this    page,    can     be     found     at
92       https://www.kernel.org/doc/man-pages/.
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96GNU                               2021-03-22                        CONFSTR(3)
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