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
   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.

   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.

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
          pathname  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 4.09 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/.

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