unixdev.net


Switch to SpeakEasy.net DSL

The Modular Manual Browser

Home Page
Manual: (Debian-5.0)
Page:
Section:
Apropos / Subsearch:
optional field

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



NAME
       getcwd, getwd, get_current_dir_name - Get current working directory

SYNOPSIS
       #include <&lt;unistd.h>&gt;

       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)):

       getcwd(): _BSD_SOURCE || _XOPEN_SOURCE >= 500
       get_current_dir_name(): _GNU_SOURCE

DESCRIPTION
       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 current absolute pathname would require  a  buffer  longer  than
       size  elements, NULL is returned, and errno is set to ERANGE; an appli-
       cation should check for this error, and allocate  a  larger  buffer  if
       necessary.

       If buf is NULL, the behavior of getcwd() is undefined.

       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  on  call.   In this case, the allocated buffer has the length
       size unless size is zero, when buf is allocated as  big  as  necessary.
       It  is possible (and, indeed, advisable) to free(3) the buffers if they
       have been obtained this way.

       get_current_dir_name(), will malloc(3) an array big enough to hold  the
       current  directory  name.   If the environment variable PWD is set, and
       its value is correct, then that value will be returned.

       getwd(), does not malloc(3) any memory.  The buf argument should  be  a
       pointer  to  an  array at least PATH_MAX bytes long.  getwd() does only
       return the first PATH_MAX bytes of  the  actual  pathname.   Note  that
       PATH_MAX need not be a compile-time constant; it may depend on the file
       system and may even be unlimited.  For portability  and  security  rea-
       sons, use of getwd() is deprecated.

RETURN VALUE
       NULL  on  failure  with errno set accordingly, and buf on success.  The
       contents of the array pointed to by buf is 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.

       ENOENT The current working directory has been unlinked.

       ERANGE The  size argument is less than the length of the working direc-
              tory name.  You need to allocate a bigger array and try again.

CONFORMING TO
       getcwd() conforms to POSIX.1-2001.  getwd() is present in POSIX.1-2001,
       but marked LEGACY.  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 file system 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
       chdir(2), fchdir(2), open(2), unlink(2), free(3), malloc(3)

COLOPHON
       This page is part of release 3.05 of the Linux  man-pages  project.   A
       description  of  the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.



GNU                               2007-07-26                         GETCWD(3)