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NAME
getcwd, getwd, get_current_dir_name - get current working directory
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#include <unistd.h>
char *getcwd(char buf[.size], size_t size);
char *get_current_dir_name(void);
[[deprecated]] char *getwd(char buf[PATH_MAX]);
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 >= 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 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.
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 of 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 │
└───────────────────────────────────────────────────────────┴───────────────┴─────────────┘
VERSIONS
POSIX.1-2001 leaves the behavior of getcwd() unspecified if buf is NULL.
POSIX.1-2001 does not define any errors for getwd().
VERSIONS
C library/kernel differences
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, PATH_MAX 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(2) 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.
STANDARDS
getcwd()
POSIX.1-2008.
get_current_dir_name()
GNU.
getwd()
None.
HISTORY
getcwd()
POSIX.1-2001.
getwd()
POSIX.1-2001, but marked LEGACY. Removed in POSIX.1-2008. Use getcwd() instead.
Under Linux, these functions make use of the getcwd() system call (available since Linux
2.1.92). On older systems they 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.
NOTES
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.
BUGS
Since the Linux 2.6.36 change that added "(unreachable)" in the circumstances described
above, the glibc implementation of getcwd() has 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.
SEE ALSO
pwd(1), chdir(2), fchdir(2), open(2), unlink(2), free(3), malloc(3)