NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | CONFORMING TO | NOTES | BUGS | SEE ALSO | COLOPHON

GETCWD(3)                 Linux Programmer's Manual                GETCWD(3)

NAME         top

       getcwd, getwd, get_current_dir_name - get current working directory

SYNOPSIS         top

       #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         top

       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         top

       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         top

       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         top

       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         top

       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         top

       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.

       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.

   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.

BUGS         top

       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         top

       pwd(1), chdir(2), fchdir(2), open(2), unlink(2), free(3), malloc(3)

COLOPHON         top

       This page is part of release 5.04 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                              2018-04-30                        GETCWD(3)

Pages that refer to this page: pwd(1)chdir(2)syscalls(2)realpath(3)core(5)