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RedHat 9 (Linux i386) - man page for getwd (redhat section 3)

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GETCWD(3)			    Linux Programmer's Manual				GETCWD(3)

       getcwd, get_current_dir_name, getwd - Get current working directory

       #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  path-
       name.   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

       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.


       chdir(2), fchdir(2), open(2), unlink(2), free(3), malloc(3)

GNU					    2002-04-22					GETCWD(3)
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