ARCHIVE_WRITE(3) | Library Functions Manual | ARCHIVE_WRITE(3) |
archive_write
—
#include <archive.h>
To write an archive, you must first obtain an initialized struct
archive object from archive_write_new
().
You can then modify this object for the desired operations with
the various archive_write_set_XXX
() functions. In
particular, you will need to invoke appropriate
archive_write_add_XXX
() and
archive_write_set_XXX
() functions to enable the
corresponding compression and format support.
Once you have prepared the struct archive object, you call
archive_write_open
() to actually open the archive
and prepare it for writing. There are several variants of this function; the
most basic expects you to provide pointers to several functions that can
provide blocks of bytes from the archive. There are convenience forms that
allow you to specify a filename, file descriptor, FILE
* object, or a block of memory from which to write the archive
data.
Individual archive entries are written in a three-step process: You first initialize a struct archive_entry structure with information about the new entry. At a minimum, you should set the pathname of the entry and provide a struct stat with a valid st_mode field, which specifies the type of object and st_size field, which specifies the size of the data portion of the object.
After all entries have been written, use the
archive_write_free
() function to release all
resources.
#ifdef __linux__ #define _FILE_OFFSET_BITS 64 #endif #include <sys/stat.h> #include <archive.h> #include <archive_entry.h> #include <fcntl.h> #include <stdlib.h> #include <unistd.h> struct mydata { const char *name; int fd; }; int myopen(struct archive *a, void *client_data) { struct mydata *mydata = client_data; mydata->fd = open(mydata->name, O_WRONLY | O_CREAT, 0644); if (mydata->fd >= 0) return (ARCHIVE_OK); else return (ARCHIVE_FATAL); } la_ssize_t mywrite(struct archive *a, void *client_data, const void *buff, size_t n) { struct mydata *mydata = client_data; return (write(mydata->fd, buff, n)); } int myclose(struct archive *a, void *client_data) { struct mydata *mydata = client_data; if (mydata->fd > 0) close(mydata->fd); return (0); } void write_archive(const char *outname, const char **filename) { struct mydata *mydata = malloc(sizeof(struct mydata)); struct archive *a; struct archive_entry *entry; struct stat st; char buff[8192]; int len; int fd; a = archive_write_new(); mydata->name = outname; /* Set archive format and filter according to output file extension. * If it fails, set default format. Platform depended function. * See supported formats in archive_write_set_format_filter_by_ext.c */ if (archive_write_set_format_filter_by_ext(a, outname) != ARCHIVE_OK) { archive_write_add_filter_gzip(a); archive_write_set_format_ustar(a); } archive_write_open(a, mydata, myopen, mywrite, myclose); while (*filename) { stat(*filename, &st); entry = archive_entry_new(); archive_entry_copy_stat(entry, &st); archive_entry_set_pathname(entry, *filename); archive_write_header(a, entry); if ((fd = open(*filename, O_RDONLY)) != -1) { len = read(fd, buff, sizeof(buff)); while (len > 0) { archive_write_data(a, buff, len); len = read(fd, buff, sizeof(buff)); } close(fd); } archive_entry_free(entry); filename++; } archive_write_free(a); } int main(int argc, const char **argv) { const char *outname; argv++; outname = *argv++; write_archive(outname, argv); return 0; }
libarchive
library first appeared in
FreeBSD 5.3.
libarchive
library was written by
Tim Kientzle ⟨kientzle@acm.org⟩.
The default pax interchange format eliminates most of the historic
tar limitations and provides a generic key/value attribute facility for
vendor-defined extensions. One oversight in POSIX is the failure to provide
a standard attribute for large device numbers. This library uses
“SCHILY.devminor” and “SCHILY.devmajor” for
device numbers that exceed the range supported by the backwards-compatible
ustar header. These keys are compatible with Joerg Schilling's
star
archiver. Other implementations may not
recognize these keys and will thus be unable to correctly restore device
nodes with large device numbers from archives created by this library.
February 2, 2012 | NetBSD 9.0 |