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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | CONFORMING TO | NOTES | SEE ALSO | COLOPHON |
GETCWD(3) Linux Programmer's Manual GETCWD(3)
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)):
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
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.
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.
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.
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 │
└───────────────────────┴───────────────┴─────────────┘
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.
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.
pwd(1), chdir(2), fchdir(2), open(2), unlink(2), free(3), malloc(3)
This page is part of release 4.12 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/.
GNU 2016-10-08 GETCWD(3)
Pages that refer to this page: chdir(2), syscalls(2), realpath(3), core(5)