#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:
               _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 ||

       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.

       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, Linux (libc4, libc5,
       glibc) getcwd() allocates 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
       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.

       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.

       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.

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

       This  page  is  part of release 3.54 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at
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