The getcwd function copies the absolute pathname of the current working directory into the memory referenced by buf and returns a pointer to buf. The size argument is the size, in bytes, of the array referenced by buf.
If buf is NULL, space is allocated as necessary to store the pathname. This space may later be free 3 d.
The function getwd is a compatibility routine which calls getcwd with its buf argument and a size of MAXPATHLEN (as defined in the include file
.In sys/param.h ) . Obviously, buf should be at least MAXPATHLEN bytes in length.
These routines have traditionally been used by programs to save the name of a working directory for the purpose of returning to it. A much faster and less error-prone method of accomplishing this is to open the current directory (.) and use the fchdir(2) function to return.
Upon successful completion, a pointer to the pathname is returned. Otherwise a NULL pointer is returned and the global variable errno is set to indicate the error. In addition, getwd copies the error message associated with errno into the memory referenced by buf.
The getcwd function will fail if: