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| author | Tomas Bzatek <tbzatek@users.sourceforge.net> | 2008-06-08 11:04:43 +0200 |
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| committer | Tomas Bzatek <tbzatek@users.sourceforge.net> | 2008-06-08 11:04:43 +0200 |
| commit | 16f738ecee689c6feb2acb7e4ef4d9bb4144ae7d (patch) | |
| tree | 3d22f54f7298f81b18ed66d05a62fa8bfab359ab /libarchive/libarchive-2.4.17/doc/text/archive_write_disk.3 | |
| download | tuxcmd-modules-0.6.36.tar.xz | |
Initial commitv0.6.36release-0.6.36-dev
Diffstat (limited to 'libarchive/libarchive-2.4.17/doc/text/archive_write_disk.3')
| -rw-r--r-- | libarchive/libarchive-2.4.17/doc/text/archive_write_disk.3 | 253 |
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diff --git a/libarchive/libarchive-2.4.17/doc/text/archive_write_disk.3 b/libarchive/libarchive-2.4.17/doc/text/archive_write_disk.3 new file mode 100644 index 0000000..18e4e50 --- /dev/null +++ b/libarchive/libarchive-2.4.17/doc/text/archive_write_disk.3 @@ -0,0 +1,253 @@ +archive_write_disk(3) FreeBSD Library Functions Manual archive_write_disk(3) + +NAME + archive_write_disk_new, archive_write_disk_set_options, + archive_write_disk_set_skip_file, archive_write_disk_set_group_lookup, + archive_write_disk_set_standard_lookup, + archive_write_disk_set_user_lookup, archive_write_header, + archive_write_data, archive_write_finish_entry, archive_write_close, + archive_write_finish -- functions for creating objects on disk + +SYNOPSIS + #include <archive.h> + + struct archive * + archive_write_disk_new(void); + + int + archive_write_disk_set_options(struct archive *, int flags); + + int + archive_write_disk_set_skip_file(struct archive *, dev_t, ino_t); + + int + archive_write_disk_set_group_lookup(struct archive *, void *, + gid_t (*)(void *, const char *gname, gid_t gid), + void (*cleanup)(void *)); + + int + archive_write_disk_set_standard_lookup(struct archive *); + + int + archive_write_disk_set_user_lookup(struct archive *, void *, + uid_t (*)(void *, const char *uname, uid_t uid), + void (*cleanup)(void *)); + + int + archive_write_header(struct archive *, struct archive_entry *); + + ssize_t + archive_write_data(struct archive *, const void *, size_t); + + int + archive_write_finish_entry(struct archive *); + + int + archive_write_close(struct archive *); + + int + archive_write_finish(struct archive *); + +DESCRIPTION + These functions provide a complete API for creating objects on disk from + struct archive_entry descriptions. They are most naturally used when + extracting objects from an archive using the archive_read() interface. + The general process is to read struct archive_entry objects from an ar- + chive, then write those objects to a struct archive object created using + the archive_write_disk() family functions. This interface is deliber- + ately very similar to the archive_write() interface used to write objects + to a streaming archive. + + archive_write_disk_new() + Allocates and initializes a struct archive object suitable for + writing objects to disk. + + archive_write_disk_set_skip_file() + Records the device and inode numbers of a file that should not be + overwritten. This is typically used to ensure that an extraction + process does not overwrite the archive from which objects are + being read. This capability is technically unnecessary but can + be a significant performance optimization in practice. + + archive_write_disk_set_options() + The options field consists of a bitwise OR of one or more of the + following values: + ARCHIVE_EXTRACT_OWNER + The user and group IDs should be set on the restored + file. By default, the user and group IDs are not + restored. + ARCHIVE_EXTRACT_PERM + Full permissions (including SGID, SUID, and sticky bits) + should be restored exactly as specified, without obeying + the current umask. Note that SUID and SGID bits can only + be restored if the user and group ID of the object on + disk are correct. If ARCHIVE_EXTRACT_OWNER is not speci- + fied, then SUID and SGID bits will only be restored if + the default user and group IDs of newly-created objects + on disk happen to match those specified in the archive + entry. By default, only basic permissions are restored, + and umask is obeyed. + ARCHIVE_EXTRACT_TIME + The timestamps (mtime, ctime, and atime) should be + restored. By default, they are ignored. Note that + restoring of atime is not currently supported. + ARCHIVE_EXTRACT_NO_OVERWRITE + Existing files on disk will not be overwritten. By + default, existing regular files are truncated and over- + written; existing directories will have their permissions + updated; other pre-existing objects are unlinked and + recreated from scratch. + ARCHIVE_EXTRACT_UNLINK + Existing files on disk will be unlinked before any + attempt to create them. In some cases, this can prove to + be a significant performance improvement. By default, + existing files are truncated and rewritten, but the file + is not recreated. In particular, the default behavior + does not break existing hard links. + ARCHIVE_EXTRACT_ACL + Attempt to restore ACLs. By default, extended ACLs are + ignored. + ARCHIVE_EXTRACT_FFLAGS + Attempt to restore extended file flags. By default, file + flags are ignored. + ARCHIVE_EXTRACT_XATTR + Attempt to restore POSIX.1e extended attributes. By + default, they are ignored. + ARCHIVE_EXTRACT_SECURE_SYMLINKS + Refuse to extract any object whose final location would + be altered by a symlink on disk. This is intended to + help guard against a variety of mischief caused by ar- + chives that (deliberately or otherwise) extract files + outside of the current directory. The default is not to + perform this check. If ARCHIVE_EXTRACT_UNLINK is speci- + fied together with this option, the library will remove + any intermediate symlinks it finds and return an error + only if such symlink could not be removed. + ARCHIVE_EXTRACT_SECURE_NODOTDOT + Refuse to extract a path that contains a .. element any- + where within it. The default is to not refuse such + paths. Note that paths ending in .. always cause an + error, regardless of this flag. + + archive_write_disk_set_group_lookup(), + archive_write_disk_set_user_lookup() + The struct archive_entry objects contain both names and ids that + can be used to identify users and groups. These names and ids + describe the ownership of the file itself and also appear in ACL + lists. By default, the library uses the ids and ignores the + names, but this can be overridden by registering user and group + lookup functions. To register, you must provide a lookup func- + tion which accepts both a name and id and returns a suitable id. + You may also provide a void * pointer to a private data structure + and a cleanup function for that data. The cleanup function will + be invoked when the struct archive object is destroyed. + + archive_write_disk_set_standard_lookup() + This convenience function installs a standard set of user and + group lookup functions. These functions use getpwnam(3) and + getgrnam(3) to convert names to ids, defaulting to the ids if the + names cannot be looked up. These functions also implement a sim- + ple memory cache to reduce the number of calls to getpwnam(3) and + getgrnam(3). + + archive_write_header() + Build and write a header using the data in the provided struct + archive_entry structure. See archive_entry(3) for information on + creating and populating struct archive_entry objects. + + archive_write_data() + Write data corresponding to the header just written. Returns + number of bytes written or -1 on error. + + archive_write_finish_entry() + Close out the entry just written. Ordinarily, clients never need + to call this, as it is called automatically by + archive_write_next_header() and archive_write_close() as needed. + + archive_write_close() + Set any attributes that could not be set during the initial + restore. For example, directory timestamps are not restored ini- + tially because restoring a subsequent file would alter that time- + stamp. Similarly, non-writable directories are initially created + with write permissions (so that their contents can be restored). + The archive_write_disk_new library maintains a list of all such + deferred attributes and sets them when this function is invoked. + + archive_write_finish() + Invokes archive_write_close() if it was not invoked manually, + then releases all resources. + More information about the struct archive object and the overall design + of the library can be found in the libarchive(3) overview. Many of these + functions are also documented under archive_write(3). + +RETURN VALUES + Most functions return ARCHIVE_OK (zero) on success, or one of several + non-zero error codes for errors. Specific error codes include: + ARCHIVE_RETRY for operations that might succeed if retried, ARCHIVE_WARN + for unusual conditions that do not prevent further operations, and + ARCHIVE_FATAL for serious errors that make remaining operations impossi- + ble. The archive_errno() and archive_error_string() functions can be + used to retrieve an appropriate error code and a textual error message. + + archive_write_disk_new() returns a pointer to a newly-allocated struct + archive object. + + archive_write_data() returns a count of the number of bytes actually + written. On error, -1 is returned and the archive_errno() and + archive_error_string() functions will return appropriate values. + +SEE ALSO + archive_read(3), archive_write(3), tar(1), libarchive(3) + +HISTORY + The libarchive library first appeared in FreeBSD 5.3. The + archive_write_disk interface was added to libarchive 2.0 and first + appeared in FreeBSD 6.3. + +AUTHORS + The libarchive library was written by Tim Kientzle <kientzle@acm.org>. + +BUGS + Directories are actually extracted in two distinct phases. Directories + are created during archive_write_header(), but final permissions are not + set until archive_write_close(). This separation is necessary to cor- + rectly handle borderline cases such as a non-writable directory contain- + ing files, but can cause unexpected results. In particular, directory + permissions are not fully restored until the archive is closed. If you + use chdir(2) to change the current directory between calls to + archive_read_extract() or before calling archive_read_close(), you may + confuse the permission-setting logic with the result that directory per- + missions are restored incorrectly. + + The library attempts to create objects with filenames longer than + PATH_MAX by creating prefixes of the full path and changing the current + directory. Currently, this logic is limited in scope; the fixup pass + does not work correctly for such objects and the symlink security check + option disables the support for very long pathnames. + + Restoring the path aa/../bb does create each intermediate directory. In + particular, the directory aa is created as well as the final object bb. + In theory, this can be exploited to create an entire directory heirarchy + with a single request. Of course, this does not work if the + ARCHIVE_EXTRACT_NODOTDOT option is specified. + + Implicit directories are always created obeying the current umask. + Explicit objects are created obeying the current umask unless + ARCHIVE_EXTRACT_PERM is specified, in which case they current umask is + ignored. + + SGID and SUID bits are restored only if the correct user and group could + be set. If ARCHIVE_EXTRACT_OWNER is not specified, then no attempt is + made to set the ownership. In this case, SGID and SUID bits are restored + only if the user and group of the final object happen to match those + specified in the entry. + + The ``standard'' user-id and group-id lookup functions are not the + defaults because getgrnam(3) and getpwnam(3) are sometimes too large for + particular applications. The current design allows the application + author to use a more compact implementation when appropriate. + + There should be a corresponding archive_read_disk interface that walks a + directory heirarchy and returns archive entry objects. + +FreeBSD 6.0 March 2, 2007 FreeBSD 6.0 |
