# getcwd

## NAME



           getcwd, getwd, get_current_dir_name - get current working
           directory
    


## LIBRARY



           Standard C library (_libc_ , _-lc_)
    


## SYNOPSIS



           **#include <unistd.h>**
    
           **char *getcwd(** size_t size;
                        **char** _buf_**[**_size_**], size_t** _size_**);**
           **char *get_current_dir_name(void);**
    
           **[[deprecated]] char *getwd(char** _buf_**[PATH_MAX]);**
    
       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 >= 2.19: */ _DEFAULT_SOURCE
                       || /* glibc <= 2.19: */ _BSD_SOURCE
               Before glibc 2.12:
                   _BSD_SOURCE || _XOPEN_SOURCE >= 500
    


## 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.
    
           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 of **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.
    
           **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



           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 │
           └──────────────────────────────────┴───────────────┴─────────────┘
    


## VERSIONS



           POSIX.1-2001 leaves the behavior of **getcwd**() unspecified if _buf_ is
           NULL.
    
           POSIX.1-2001 does not define any errors for **getwd**().
    


## VERSIONS



       **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 pathnames from
           untrusted sources, callers of the functions described in this page
           (before glibc 2.27) or the raw **getcwd**() system call should
           consider checking whether the returned pathname starts with '/' or
           '(' to avoid misinterpreting an unreachable path as a relative
           pathname.
    


## STANDARDS



           **getcwd**()
                  POSIX.1-2008.
    
           **get_current_dir_name**()
                  GNU.
    
           **getwd**()
                  None.
    


## NOTES



           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.
    


## BUGS



           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**.
    


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