Originální popis anglicky:
getcwd, get_current_dir_name, getwd - Get current working directory
Návod, kniha: Linux Programmer's Manual
#include <unistd.h>
char *getcwd(char *buf, size_t size);
char *get_current_dir_name(void);
char *getwd(char *buf);
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 current absolute path name would require a buffer longer than
size
elements,
NULL is returned, and
errno is set to
ERANGE;
an application should check for this error, and allocate a larger buffer if
necessary.
If
buf is NULL, the behaviour of
getcwd() is undefined.
As an extension to the POSIX.1 standard, Linux (libc4, libc5, glibc)
getcwd() allocates the buffer dynamically using
malloc() if
buf is
NULL on call. In this case, the allocated buffer has the
length
size unless
size is zero, when
buf is allocated as
big as necessary. It is possible (and, indeed, advisable) to
free() the
buffers if they have been obtained this way.
get_current_dir_name, which is only prototyped if
_GNU_SOURCE is
defined, will
malloc(3) an array big enough to hold the current
directory name. If the environment variable
PWD is set, and its value
is correct, then that value will be returned.
getwd, which is only prototyped if
_BSD_SOURCE or
_XOPEN_SOURCE_EXTENDED is defined, will not
malloc(3) any
memory. The
buf argument should be a pointer to an array at least
PATH_MAX bytes long.
getwd does only return the first
PATH_MAX bytes of the actual pathname. Note that
PATH_MAX need
not be a compile-time constant; it may depend on the filesystem and may even
be unlimited. For portability and security reasons, use of
getwd is
deprecated.
NULL on failure with
errno set accordingly, and
buf on
success. The contents of the array pointed to by
buf is undefined on
error.
- EACCES
- Permission to read or search a component of the file name
was denied.
- EFAULT
- buf points to a bad address.
- EINVAL
- The size argument is zero and buf is not a
null pointer.
- ENOENT
- The current working directory has been unlinked.
- ERANGE
- The size argument is less than the length of the
working directory name. You need to allocate a bigger array and try
again.
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 file system 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.
POSIX.1
chdir(2),
fchdir(2),
open(2),
unlink(2),
free(3),
malloc(3)
