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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:
_BSD_SOURCE ||
(_XOPEN_SOURCE >= 500 ||
_XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED) &&
!(_POSIX_C_SOURCE >= 200809L || _XOPEN_SOURCE >= 700)
Before glibc 2.12:
_BSD_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
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.
ENOMEM Out of memory.
ENOENT The current working directory has been unlinked.
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
chdir(2), fchdir(2), open(2), unlink(2), free(3), malloc(3)
COLOPHON
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