llvm/docs/CommandGuide/llvm-ar.pod

=pod

=head1 NAME

llvm-ar - LLVM archiver

=head1 SYNOPSIS

B<llvm-ar> [-X32_64] [-]{dmpqrtx}[Rabfouz] [relpos] [count] <archive-file> [files...]


=head1 DESCRIPTION

The B<llvm-ar> command is similar to the common Unix utility, C<ar>. It 
archives several files together into a single file. The intent for this is
to produce archive libraries by LLVM bytecode that can be linked into an
LLVM program. However, the archive can contain any kind of file. If requested,
B<llvm-ar> can generate a symbol table that makes linking faster because
only the symbol table needs to be consulted, not each individual file member
of the archive. 

While the B<llvm-ar> command produces files that are similar to the format
used by older C<ar> implementations, it has several significant departures 
in order to make the archive appropriate for LLVM. Consequently, archives 
produced with B<llvm-ar> probably won't be readable or editable with any
C<ar> implementation unless the archive content is very simple.

Here's where B<llvm-ar> departs from previous C<ar> implementations:

=over

=item I<Symbol Table>

Since B<llvm-ar> is intended to archive bytecode files, the symbol table
won't make much sense to anything but LLVM. Consequently, the symbol table's
format has been simplified. It consists simply of a sequence of pairs
of a file member index number as an LSB 4byte integer and a null-terminated 
string.

=item I<Long Paths>

Some C<ar> implementations (SVR4) use a separate file member to record long
path names (> 15 characters). B<llvm-ar> takes the BSD 4.4 and Mac OS X 
approach which is to simply store the full path name immediately preceding
the data for the file. The path name is null terminated and may contain the
slash (/) character. 

=item I<Compression>

B<llvm-ar> can compress the members of an archive to save space. The 
compression used depends on what's available on the platform but favors
bzip2 and then zlib. Note that for very small files, bzip2 may increase 
the file size but generally does about 10% better than zlib on LLVM 
bytecode files.

=item I<Directory Recursion>

Most C<ar> implementations do not recurse through directories but simply
ignore directories if they are presented to the program in the F<files> 
option. B<llvm-ar>, however, can recurse through directory structures and
add all the files under a directory, if requested.

=item I<TOC Verbose Output>

When B<llvm-ar> prints out the verbose table of contents (C<tv> option), it
precedes the usual output with a character indicating the basic kind of 
content in the file. A blank means the file is a regular file. A 'Z' means
the file is compressed. A 'B' means the file is an LLVM bytecode file. An
'S' means the file is the symbol table.

=back

=head1 OPTIONS

The options to B<llvm-ar> are compatible with other C<ar> implementations.
However, there are a few modifiers (F<zR>) that are not found in other
C<ar>s. The options to B<llvm-ar> specify a single basic operation to 
perform on the archive, a variety of modifiers for that operation, the
name of the archive file, and an optional list of file names. These options
are used to determine how B<llvm-ar> should process the archive file.

The Operations and Modifiers are explained in the sections below. The minimal
set of options is at least one operator and the name of the archive. Typically
archive files end with a C<.a> suffix, but this is not required. Following
the F<achive-name> comes a list of F<files> that indicate the specific members
of the archive to operate on. If the F<files> option is not specified, it
generally means either "none" or "all" members, depending on the operation.

=head2 Operations

=over

=item d

Delete files from the archive. No modifiers are applicable to this operation.
The F<files> options specify which members should be removed from the
archive. It is not an error if a specified file does not appear in the archive.
If no F<files> are specified, the archive is not modified.

=item m[abi]

Move files from one location in the archive to another. The F<a>, F<b>, and 
F<i> modifiers apply to this operation. The F<files> will all be moved
to the location given by the modifiers. If no modifiers are used, the files
will be moved to the end of the archive. If no F<files> are specified, the
archive is not modified.

=item p

Print files to the standard output. No modifiers are applicable to this
operation. This operation simply prints the F<files> indicated to the
standard output. If no F<files> are specified, the entire archive is printed.
Printing bytecode files is ill-advised as they might confuse your terminal
settings. The F<p> operation never modifies the archive.

=item q[Rfz]

Quickly append files to the end of the archive. The F<R>, F<f>, and F<z>
modifiers apply to this operation.  This operation quickly adds the 
F<files> to the archive without checking for duplicates that shoud be 
removed first. If no F<files> are specified, the archive is not modified. 
Becasue of the way that B<llvm-ar> constructs the archive file, its dubious 
whether the F<q> operation is any faster than the F<r> operation.

=item r[Rabfuz]

Replace or insert file members. The F<R>, F<a>, F<b>, F<f>, F<u>, and F<z>
modifiers apply to this operation. This operation will replace existing
F<files> or insert them at the end of the archive if they do not exist. If no
F<files> are specified, the archive is not modified.

=item t[v]

Print the table of contents. Without any modifiers, this operation just prints
the names of the members to the standard output. With the F<v> modifier,
B<llvm-ar> also prints out the file type (B=bytecode, Z=compressed, S=symbol
table, blank=regular file), the permission mode, the owner and group, the
size, and the date. If any F<files> are specified, the listing is only for
those files. If no F<files> are specified, the table of contents for the
whole archive is printed.

=item x[o]

Extract archive members back to files. The F<o> modifier applies to this
operation. This operation retrieves the indicated F<files> from the archive 
and writes them back to the operating system's file system. If no 
F<files> are specified, the entire archive is extract. 

=back

=head2 Modifiers (operation specific)

=over

=item [a] 

put F<files> after [relpos]

=item [b] 

put F<files> before [relpos] (same as [i])

=item [f] 

truncate inserted file names

=item [i] 

put file(s) before [relpos] (same as [b])

=item [N] 

use instance [count] of name

=item [o] 

preserve original dates

=item [P] 

use full path names when matching

=item [R] 

recurse through directories when inserting

=item [u] 

update only files newer than archive contents

=item [z] 

compress/uncompress files before inserting/extracting

=back

=head2 Modifiers (generic)

=over

=item [c]

do not warn if the library had to be created

=item [s]

create an archive index (cf. ranlib)

=item [S]

do not build a symbol table

=item [R]

recursively process directories

=item [v]

be verbose

=back

=head1 EXIT STATUS

If B<llvm-as> succeeds, it will exit with 0.  A usage error, results
in an exit code of 1. A hard (file system typically) error results in an
exit code of 2. Miscellaneous or unknown errors result in an
exit code of 3.

=head1 SEE ALSO

L<llvm-ld|llvm-ld>

=head1 AUTHORS

Maintained by the LLVM Team (L<http://llvm.cs.uiuc.edu>).

=cut