GETCWD(3) Linux Programmers Manual GETCWD(3)
getcwd, getwd, get_current_dir_name - Get current working directory
char *getcwd(char *buf, size_t size);
char *getwd(char *buf);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
getcwd(): _BSD_SOURCE || _XOPEN_SOURCE >= 500
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
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.
NULL on failure with errno set accordingly, and buf on success. The
contents of the array pointed to by buf is 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.
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.
getcwd() conforms to POSIX.1-2001. getwd() is present in POSIX.1-2001,
but marked LEGACY. 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 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.
chdir(2), fchdir(2), open(2), unlink(2), free(3), malloc(3)
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)