NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | CONFORMING TO | NOTES | 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.

       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         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.

       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         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, 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         top

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

COLOPHON         top

       This page is part of release 4.07 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                              2016-03-15                        GETCWD(3)