getcwd

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

NAME
       getcwd, getwd, get_current_dir_name - get current working directory

SYNOPSIS
       #include <unistd.h>

       char *getcwd(char *buf, size_t size);

       char *getwd(char *buf);

       char *get_current_dir_name(void);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       get_current_dir_name():
              _GNU_SOURCE

       getwd():
           Since glibc 2.12:
               _BSD_SOURCE ||
                   (_XOPEN_SOURCE >= 500 ||
                       _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED) &&
                   !(_POSIX_C_SOURCE >= 200809L || _XOPEN_SOURCE >= 700)
           Before glibc 2.12:
               _BSD_SOURCE || _XOPEN_SOURCE >= 500 ||
               _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED

DESCRIPTION
       These functions return a null-terminated string containing an  absolute
       pathname  that is the current working directory of the calling process.
       The pathname is returned as the function result and  via  the  argument
       buf, if present.

       If the current directory is not below the root directory of the current
       process (e.g., because the process set  a  new  filesystem  root  using
       chroot(2)  without  changing  its current directory into the new root),
       then, since Linux 2.6.36, the returned path will be prefixed  with  the
       string "(unreachable)".  Such behavior can also be caused by an unpriv-
       ileged user by changing the current directory into another mount names-
       pace.  When dealing with paths from untrusted sources, callers of these
       functions should consider checking whether  the  returned  path  starts
       with '/' or '(' to avoid misinterpreting an unreachable path as a rela-
       tive path.

       The getcwd() function copies an absolute pathname of the current  work-
       ing directory to the array pointed to by buf, which is of length size.

       If  the  length  of the absolute pathname of the current working direc-
       tory, including the terminating null byte, exceeds size bytes, NULL  is
       returned,  and  errno is set to ERANGE; an application should check for
       this error, and allocate a larger buffer if necessary.

       As an extension to the POSIX.1-2001 standard,  glibc's  getcwd()  allo-
       cates  the  buffer dynamically using malloc(3) if buf is NULL.  In this
       case, the allocated buffer has the length size  unless  size  is  zero,
       when  buf  is allocated as big as necessary.  The caller should free(3)
       the returned buffer.

       get_current_dir_name() will malloc(3) an array big enough to  hold  the
       absolute pathname of the current working directory.  If the environment
       variable PWD is set, and its value is correct, then that value will  be
       returned.  The caller should free(3) the returned buffer.

       getwd()  does  not  malloc(3) any memory.  The buf argument should be a
       pointer to an array at least PATH_MAX bytes long.  If the length of the
       absolute  pathname of the current working directory, including the ter-
       minating null byte, exceeds PATH_MAX bytes, NULL is returned, and errno
       is  set  to ENAMETOOLONG.  (Note that on some systems, PATH_MAX may not
       be a compile-time constant; furthermore, its value may  depend  on  the
       filesystem,  see  pathconf(3).)   For portability and security reasons,
       use of getwd() is deprecated.

RETURN VALUE
       On success, these functions return a pointer to a string containing the
       pathname  of  the  current working directory.  In the case getcwd() and
       getwd() this is the same value as buf.

       On failure, these functions return NULL, and errno is set  to  indicate
       the  error.   The contents of the array pointed to by buf are undefined
       on error.

ERRORS
       EACCES Permission to read or search a component  of  the  filename  was
              denied.

       EFAULT buf points to a bad address.

       EINVAL The size argument is zero and buf is not a null pointer.

       EINVAL getwd(): buf is NULL.

       ENAMETOOLONG
              getwd():  The  size  of  the  null-terminated  absolute pathname
              string exceeds PATH_MAX bytes.

       ENOMEM Out of memory.

       ENOENT The current working directory has been unlinked.

       ERANGE The size argument is less than the length of the absolute  path-
              name  of  the  working directory, including the terminating null
              byte.  You need to allocate a bigger array and try again.

ATTRIBUTES
       For  an  explanation  of  the  terms  used   in   this   section,   see
       attributes(7).

       +-----------------------+---------------+-------------+
       |Interface              | Attribute     | Value       |
       +-----------------------+---------------+-------------+
       |getcwd(), getwd()      | Thread safety | MT-Safe     |
       +-----------------------+---------------+-------------+
       |get_current_dir_name() | Thread safety | MT-Safe env |
       +-----------------------+---------------+-------------+
CONFORMING TO
       getcwd()  conforms  to  POSIX.1-2001.   Note  however that POSIX.1-2001
       leaves the behavior of getcwd() unspecified if buf is NULL.

       getwd() is present in POSIX.1-2001, but  marked  LEGACY.   POSIX.1-2008
       removes   the   specification   of   getwd().   Use  getcwd()  instead.
       POSIX.1-2001 does not define any errors for getwd().

       get_current_dir_name() is a GNU extension.

NOTES
       Under Linux, the function getcwd() is a system call (since 2.1.92).  On
       older  systems  it would query /proc/self/cwd.  If both system call and
       proc filesystem are missing, a generic implementation is called.   Only
       in that case can these calls fail under Linux with EACCES.

       These  functions  are  often  used  to save the location of the current
       working directory for the purpose of returning to  it  later.   Opening
       the  current directory (".") and calling fchdir(2) to return is usually
       a faster and more reliable  alternative  when  sufficiently  many  file
       descriptors are available, especially on platforms other than Linux.

SEE ALSO
       chdir(2), fchdir(2), open(2), unlink(2), free(3), malloc(3)

COLOPHON
       This  page  is  part of release 4.04 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
       http://www.kernel.org/doc/man-pages/.

GNU                               2015-04-19                         GETCWD(3)
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