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       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 unprivileged user
       by  changing  the current directory into another mount namespace.  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
       relative path.  This is no longer true under some C libraries; see NOTES.

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

       If  the  length  of  the absolute pathname of the current working directory, 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() 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 terminating 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

       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 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.

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

       ENOENT The current working directory has been unlinked.

       ENOMEM Out of memory.

       ERANGE The  size  argument is less than the length of the absolute pathname 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 attributes(7).

       │InterfaceAttributeValue       │
       │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

       Since  a  Linux 2.6.36 change that added "(unreachable)", the glibc getcwd() has failed to
       conform to POSIX and returned a relative path when the API contract requires  an  absolute
       path.   With  glibc 2.27 onwards this is corrected; calling getcwd() from such a path will
       now result in failure with ENOENT.

       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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