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, read‐
func() and writefunc(), which are pointers to the functions for open‐
ing, 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 nor‐
mally 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 struc‐
ture. 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 con‐
tains 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 dupli‐
cated 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.
ERRORStar_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 speci‐
fied tar archive type fail.
SEE ALSOopen(2), close(2), calloc(3)University of Illinois Jan 2001 tar_open(3)
