.\" Copyright (c) 2003-2004 Tim Kientzle
.\" All rights reserved.
.\"
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.\" $FreeBSD: src/lib/libarchive/archive_util.3,v 1.3 2005/01/08 19:51:04 kientzle Exp $
.\"
.Dd January 8, 2005
.Dt archive_util 3
.Os
.Sh NAME
.Nm archive_compression ,
.Nm archive_compression_name ,
.Nm archive_errno ,
.Nm archive_error_string ,
.Nm archive_format ,
.Nm archive_format_name ,
.Nm archive_set_error
.Nd libarchive utility functions
.Sh SYNOPSIS
.In archive.h
.Ft int
.Fn archive_compression "struct archive *"
.Ft const char *
.Fn archive_compression_name "struct archive *"
.Ft int
.Fn archive_errno "struct archive *"
.Ft const char *
.Fn archive_error_string "struct archive *"
.Ft int
.Fn archive_format "struct archive *"
.Ft const char *
.Fn archive_format_name "struct archive *"
.Ft int
.Fn archive_set_error "struct archive *" "int error_code" "const char *fmt" "..."
.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_compression
Returns a numeric code indicating the current compression.
This value is set by
.Fn archive_read_open .
.It Fn archive_compression_name
Returns a text description of the current compression suitable for display.
.It Fn archive_errno
Returns a numeric error code (see
.Xr errno 2 )
indicating the reason for the most recent error return.
.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_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_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 .