getcwd, get_current_dir_name, getwd - Get current working
directory
SYNOPSIS
#include <unistd.h>
char *getcwd(char *buf, size_t size);
char *get_current_dir_name(void);
char *getwd(char *buf);
DESCRIPTION
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.
RETURN VALUE
NULL on failure (for example, if the current directory is
not readable), with errno set accordingly, and buf on suc
cess. The contents of the array pointed to by buf is unde
fined on error.
CONFORMING TO
POSIX.1
SEE ALSO
chdir(2), free(3), malloc(3)
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