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

       getcwd, getwd, get_current_dir_name - get current working directory

       #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)):


           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

       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.

       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.

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

       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.

              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.

       For   an   explanation   of   the  terms  used  in  this  section,  see

       |Interface              | Attribute     | Value       |
       |getcwd(), getwd()      | Thread safety | MT-Safe     |
       |get_current_dir_name() | Thread safety | MT-Safe env |
       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.

       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.

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

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GNU                               2017-09-15                         GETCWD(3)
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