GETCWD
Section: Linux Programmer's Manual (3)
Updated: 2017-09-15
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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 4.13 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/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- ATTRIBUTES
-
- CONFORMING TO
-
- NOTES
-
- SEE ALSO
-
- COLOPHON
-
|
|
- Running on 
-
:
: 