NAME¶

getcwd, getwd, get_current_dir_name - get current working directory

LIBRARY¶

Standard C library (libc, -lc)

SYNOPSIS¶

#include <unistd.h>

char *getcwd(char buf[.size], size_t size);
char *get_current_dir_name(void);

[[deprecated]] char *getwd(char buf[PATH_MAX]);

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).

STANDARDS¶

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¶

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.

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.

SEE ALSO¶

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