getcwd, getwd, get_current_dir_name - get current working directory
#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)):
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
buf, if present.
The getcwd() function copies an absolute pathname of
the current working directory to the array pointed to by
which is of length
If the length of the absolute pathname of the current working
directory, including the terminating null byte, exceeds
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
buf is NULL. In this case, the
allocated buffer has the length
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
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
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.
On failure, these functions return NULL, and
errno is set to
indicate the error. The contents of the array pointed to by
are undefined on error.
Permission to read or search a component of the filename was denied.
buf points to a bad address.
size argument is zero and
buf is not a null
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.
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.
get_current_dir_name() 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
/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
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, 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.
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.
This page is part of release 5.10 of the Linux
project. A description of the project, information about reporting bugs,
and the latest version of this page, can be found at