Manpages - tar_open.3

tar_open, tar_close - access a tar archive via a handle

#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“);”/

This man page documents version 1.2 of libtar.

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 information 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.

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.

*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.

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