tar_open(3)							  C Library Calls						       tar_open(3)

NAME

       tar_open, tar_close - access a tar archive via a handle

SYNOPSIS

       #include <libtar.h>

       int tar_open(TAR **t, char *pathname, tartype_t *type, int oflags, int mode, int options);

       int tar_fdopen(TAR **t, int fd, char *pathname, tartype_t *type, int oflags, int mode, int options);

       int tar_fd(TAR *t");"

       int tar_close(TAR *t");"

VERSION

       This man page documents version 1.2 of libtar.

DESCRIPTION

       The tar_open() function opens a tar archive file corresponding to the filename named by the pathname argument.  The oflags argument must be
       either O_RDONLY or O_WRONLY.

       The type argument specifies the access methods for the given file type.	The tartype_t structure has  members  named  openfunc,	closefunc,
       readfunc() and writefunc(), which are pointers to the functions for opening, closing, reading, and writing the file, respectively.  If type
       is NULL, the file type defaults to a normal file, and the standard open(), close(), read(), and write() functions are used.

       The options argument is a logical-or'ed combination of zero or more of the following:

       TAR_GNU
	      Use GNU extensions.

       TAR_VERBOSE
	      Send status messages to stdout.

       TAR_NOOVERWRITE
	      Do not overwrite pre-existing files.

       TAR_IGNORE_EOT
	      Skip all-zero blocks instead of treating them as EOT.

       TAR_IGNORE_MAGIC
	      Do not validate the magic field in file headers.

       TAR_CHECK_VERSION
	      Check the version field in file headers.	(This field is normally ignored.)

       TAR_IGNORE_CRC
	      Do not validate the CRC of file headers.

       The tar_open() function allocates memory for a TAR handle, and a pointer to the allocated memory is saved in the location specified  by	t.
       The TAR handle may be passed to other libtar calls to modify the opened tar archive.  The TAR handle maintains all of the information about
       the open tar archive, including the archive type, options, and oflags selected when tar_open() was called.

       The TAR handle generated by tar_open() contains a file header structure.  When reading a tar archive, this structure contains the last file
       header  read  from the tar archive.  When writing a tar archive, this structure is used as a staging area to construct the next file header
       to be written to the archive.  In addition, the TAR handle contains a hash table which is used to keep track of the device and inode infor-
       mation  for each file which gets written to the tar archive.  This is used to detect hard links, so that files do not need to be duplicated
       in the archive.

       The tar_fdopen() function is identical to the tar_open() function, except that fd is used as the previously-opened file descriptor for  the
       tar file instead of calling type->openfunc() to open the file.

       The tar_fd() function returns the file descriptor associated with the TAR handle t.

       The tar_close() function closes the file descriptor associated with the TAR handle t and frees all dynamically-allocated memory.

RETURN VALUE

       The tar_open(), tar_fdopen(), and tar_close() functions return 0 on success.  On failure, they return -1 and set errno.

       The tar_fd() function returns the file descriptor associated with the TAR handle t.

ERRORS

       tar_open() will fail if:

       EINVAL The oflags argument was something other than O_RDONLY or O_WRONLY.

       In  addition,  tar_open()  and  tar_close() may fail if it cannot allocate memory using calloc(), or if the open or close functions for the
       specified tar archive type fail.

SEE ALSO

       open(2), close(2), calloc(3)

University of Illinois						     Jan 2001							       tar_open(3)