getcwd(3)                                             Library Functions Manual                                            getcwd(3)

       getcwd, getwd, get_current_dir_name - get current working directory

       Standard C library (libc, -lc)

       #include <unistd.h>

       char *getcwd(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)):


           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

       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  buf‐
       fer 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  neces‐
       sary.  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 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.

       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.

              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 terminat‐
              ing 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

       getwd() is present in POSIX.1-2001, but marked LEGACY.  POSIX.1-2008 removes the specification of getwd().  Use getcwd() in‐
       stead.  POSIX.1-2001 does not define any errors for getwd().

       get_current_dir_name() is a GNU extension.

       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 lat‐
       er.   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 "(un‐
       reachable)" 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 path‐
       name starts with '/' or '(' to avoid misinterpreting an unreachable path as a relative pathname.

       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 path‐
       name.  With glibc 2.27 onwards this is corrected; calling getcwd() from such a pathname will  now  result  in  failure  with

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

Linux man-pages 6.03                                         2023-02-05                                                   getcwd(3)