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
- 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.
() function copies an absolute pathname of the current working
directory to the array pointed to by buf
, which is of length
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
the buffer dynamically using malloc
(3) if buf
is NULL. In this
case, the allocated buffer has the length size
zero, when buf
is allocated as big as necessary. The caller should
(3) the returned buffer.
() will malloc
(3) an array big enough to hold
the absolute pathname of the current working directory. If the environment
is set, and its value is correct, then that value will be
returned. The caller should free
(3) the returned buffer.
() does not malloc
(3) any memory. The buf
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,
is set to ENAMETOOLONG
. (Note that on some systems,
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 of getcwd
() 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
- Permission to read or search a component of the filename was denied.
- buf points to a bad address.
- The size argument is zero and buf is not a null
- getwd(): buf is NULL.
- getwd(): The size of the null-terminated absolute pathname string
exceeds PATH_MAX bytes.
- The current working directory has been unlinked.
- Out of memory.
- 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
|getcwd (), getwd ()
() conforms to POSIX.1-2001. Note however that POSIX.1-2001 leaves
the behavior of getcwd
() unspecified if buf
() is present in POSIX.1-2001, but marked LEGACY. POSIX.1-2008
removes the specification of getwd
(). Use getcwd
POSIX.1-2001 does not define any errors for getwd
() is a GNU extension.
Under Linux, these functions make use of the getcwd
() system call
(available since Linux 2.1.92). On older systems they would query
. 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.
On Linux, the kernel provides a getcwd
() system call, which the functions
described in this page will use if possible. The system call takes the same
arguments as the library function of the same name, but is limited to
returning at most PATH_MAX
bytes. (Before Linux 3.12, the limit on the
size of the returned pathname was the system page size. On many architectures,
and the system page size are both 4096 bytes, but a few
architectures have a larger page size.) If the length of the pathname of the
current working directory exceeds this limit, then the system call fails with
the error ENAMETOOLONG
. In this case, the library functions fall back
to a (slower) alternative implementation that returns the full pathname.
Following a change in Linux 2.6.36, the pathname returned by the getcwd
system call will be prefixed with the string "(unreachable)" 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
without changing its current directory into the new root). Such behavior can
also be caused by an unprivileged user by changing the current directory into
another mount namespace. When dealing with pathname from untrusted sources,
callers of the functions described in this page should consider checking
whether the returned pathname starts with '/' or '(' to avoid misinterpreting
an unreachable path as a relative pathname.
Since the Linux 2.6.36 change that added "(unreachable)" in the
circumstances described above, the glibc implementation of getcwd
failed to conform to POSIX and returned a relative pathname when the API
contract requires an absolute pathname. With glibc 2.27 onwards this is
corrected; calling getcwd
() from such a pathname will now result in
failure with ENOENT