getcwd(3) - NetBSD Manual Pages

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

getcwd, getwd -- get working directory pathname
Standard C Library (libc, -lc)
#include <unistd.h> char * getcwd(char *buf, size_t size); char * getwd(char *buf);
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.
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.
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.
chdir(2), fchdir(2), malloc(3), strerror(3)
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.
The getwd() function appeared in 4.0BSD.
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 9.1 April 29, 2010 NetBSD 9.1
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