getcwd(3) - NetBSD Manual Pages

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GETCWD(3)               NetBSD Library Functions Manual              GETCWD(3)


NAME

     getcwd, getwd -- get working directory pathname


LIBRARY

     Standard C Library (libc, -lc)


SYNOPSIS

     #include <unistd.h>

     char *
     getcwd(char *buf, size_t size);

     char *
     getwd(char *buf);


DESCRIPTION

     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
     <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.


RETURN VALUES

     Upon successful completion, a pointer to the pathname is returned.  Oth-
     erwise a NULL pointer is returned and the global variable errno is set to
     indicate the error.  In addition, getwd() copies the error message asso-
     ciated with errno into the memory referenced by buf.


ERRORS

     The getcwd() function will fail if:

     [EACCES]           Read or search permission was denied for a component
                        of the pathname.

     [EINVAL]           The size argument is zero.

     [ENOENT]           A component of the pathname no longer exists.

     [ENOMEM]           Insufficient memory is available.

     [ERANGE]           The size argument is greater than zero but smaller
                        than the length of the pathname plus 1.


SEE ALSO

     chdir(2), fchdir(2), malloc(3), strerror(3)


STANDARDS

     The getwd() and getcwd() functions conform to ISO/IEC 9945-1:1990
     (``POSIX.1'').  The IEEE Std 1003.1-2004 (``POSIX.1'') revision marked
     getwd() as legacy and recommended the use of getcwd() instead.  The IEEE
     Std 1003.1-2008 (``POSIX.1'') revision removed getwd() from the specifi-
     cation.

     The ability to specify a NULL pointer and have getcwd() allocate memory
     as necessary is an extension.


HISTORY

     The getwd() function appeared in 4.0BSD.


SECURITY CONSIDERATIONS

     As getwd() does not know the length of the supplied buffer, it is possi-
     ble for a long (but valid) path to overflow the buffer and provide a
     means for an attacker to exploit the caller.  getcwd() should be used in
     place of getwd() (the latter is only provided for compatibility pur-
     poses).

NetBSD 8.0                      April 29, 2010                      NetBSD 8.0