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:
	       (_XOPEN_SOURCE >= 500) && ! (_POSIX_C_SOURCE >= 200809L)
		   || /* Glibc since 2.19: */ _DEFAULT_SOURCE
		   || /* Glibc versions <= 2.19: */ _BSD_SOURCE
	   Before glibc 2.12:
	       _BSD_SOURCE || _XOPEN_SOURCE >= 500

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.

       ENOENT The current working directory has been unlinked.

       ENOMEM Out of memory.

       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
       pwd(1), chdir(2), fchdir(2), open(2), unlink(2), free(3), malloc(3)

COLOPHON
       This page is part of release 4.10 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
       https://www.kernel.org/doc/man-pages/.



GNU				  2016-10-08			     GETCWD(3)