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.Dd February 2, 2012

.Dt ARCHIVE_UTIL 3

.Os

.Sh NAME

.Nm archive_clear_error ,

.Nm archive_compression ,

.Nm archive_compression_name ,

.Nm archive_copy_error ,

.Nm archive_errno ,

.Nm archive_error_string ,

.Nm archive_file_count ,

.Nm archive_filter_code ,

.Nm archive_filter_count ,

.Nm archive_filter_name ,

.Nm archive_format ,

.Nm archive_format_name ,

.Nm archive_position ,

.Nm archive_set_error

.Nd libarchive utility functions

.Sh LIBRARY

Streaming Archive Library (libarchive, -larchive)

.Sh SYNOPSIS

.In archive.h

.Ft void

.Fn archive_clear_error "struct archive *"

.Ft int

.Fn archive_compression "struct archive *"

.Ft const char *

.Fn archive_compression_name "struct archive *"

.Ft void

.Fn archive_copy_error "struct archive *" "struct archive *"

.Ft int

.Fn archive_errno "struct archive *"

.Ft const char *

.Fn archive_error_string "struct archive *"

.Ft int

.Fn archive_file_count "struct archive *"

.Ft int

.Fn archive_filter_code "struct archive *" "int"

.Ft int

.Fn archive_filter_count "struct archive *" "int"

.Ft const char *

.Fn archive_filter_name "struct archive *" "int"

.Ft int

.Fn archive_format "struct archive *"

.Ft const char *

.Fn archive_format_name "struct archive *"

.Ft int64_t

.Fn archive_position "struct archive *" "int"

.Ft void

.Fo archive_set_error

.Fa "struct archive *"

.Fa "int error_code"

.Fa "const char *fmt"

.Fa "..."

.Fc

.Sh DESCRIPTION

These functions provide access to various information about the

.Tn struct archive

object used in the

.Xr libarchive 3

library.

.Bl -tag -compact -width indent

.It Fn archive_clear_error

Clears any error information left over from a previous call.

Not generally used in client code.

.It Fn archive_compression

Synonym for

.Fn archive_filter_code(a, 0) .

.It Fn archive_compression_name

Synonym for

.Fn archive_filter_name(a, 0) .

.It Fn archive_copy_error

Copies error information from one archive to another.

.It Fn archive_errno

Returns a numeric error code (see

.Xr errno 2 )

indicating the reason for the most recent error return.

Note that this can not be reliably used to detect whether an

error has occurred.

It should be used only after another libarchive function

has returned an error status.

.It Fn archive_error_string

Returns a textual error message suitable for display.

The error message here is usually more specific than that

obtained from passing the result of

.Fn archive_errno

to

.Xr strerror 3 .

.It Fn archive_file_count

Returns a count of the number of files processed by this archive object.

The count is incremented by calls to

.Xr archive_write_header 3

or

.Xr archive_read_next_header 3 .

.It Fn archive_filter_code

Returns a numeric code identifying the indicated filter.

See

.Fn archive_filter_count

for details of the numbering.

.It Fn archive_filter_count

Returns the number of filters in the current pipeline.

For read archive handles, these filters are added automatically

by the automatic format detection.

For write archive handles, these filters are added by calls to the various

.Fn archive_write_add_filter_XXX

functions.

Filters in the resulting pipeline are numbered so that filter 0

is the filter closest to the format handler.

As a convenience, functions that expect a filter number will

accept -1 as a synonym for the highest-numbered filter.

.Pp

For example, when reading a uuencoded gzipped tar archive, there

are three filters:

filter 0 is the gunzip filter,

filter 1 is the uudecode filter,

and filter 2 is the pseudo-filter that wraps the archive read functions.

In this case, requesting

.Fn archive_position(a, -1)

would be a synonym for

.Fn archive_position(a, 2)

which would return the number of bytes currently read from the archive, while

.Fn archive_position(a, 1)

would return the number of bytes after uudecoding, and

.Fn archive_position(a, 0)

would return the number of bytes after decompression.

.It Fn archive_filter_name

Returns a textual name identifying the indicated filter.

See

.Fn archive_filter_count

for details of the numbering.

.It Fn archive_format

Returns a numeric code indicating the format of the current

archive entry.

This value is set by a successful call to

.Fn archive_read_next_header .

Note that it is common for this value to change from

entry to entry.

For example, a tar archive might have several entries that

utilize GNU tar extensions and several entries that do not.

These entries will have different format codes.

.It Fn archive_format_name

A textual description of the format of the current entry.

.It Fn archive_position

Returns the number of bytes read from or written to the indicated filter.

In particular,

.Fn archive_position(a, 0)

returns the number of bytes read or written by the format handler, while

.Fn archive_position(a, -1)

returns the number of bytes read or written to the archive.

See

.Fn archive_filter_count

for details of the numbering here.

.It Fn archive_set_error

Sets the numeric error code and error description that will be returned

by

.Fn archive_errno

and

.Fn archive_error_string .

This function should be used within I/O callbacks to set system-specific

error codes and error descriptions.

This function accepts a printf-like format string and arguments.

However, you should be careful to use only the following printf

format specifiers:

.Dq %c ,

.Dq %d ,

.Dq %jd ,

.Dq %jo ,

.Dq %ju ,

.Dq %jx ,

.Dq %ld ,

.Dq %lo ,

.Dq %lu ,

.Dq %lx ,

.Dq %o ,

.Dq %u ,

.Dq %s ,

.Dq %x ,

.Dq %% .

Field-width specifiers and other printf features are

not uniformly supported and should not be used.

.El

.Sh SEE ALSO

.Xr archive_read 3 ,

.Xr archive_write 3 ,

.Xr libarchive 3 ,

.Xr printf 3

.Sh HISTORY

The

.Nm libarchive

library first appeared in

.Fx 5.3 .

.Sh AUTHORS

.An -nosplit

The

.Nm libarchive

library was written by

.An Tim Kientzle Aq kientzle@acm.org .