ar

Create archive from files

$ ar rcs [archive.a] [file1.o] [file2.o]

$ ar t [archive.a]

$ ar x [archive.a]

$ ar x [archive.a] [file.o]

$ ar r [archive.a] [newfile.o]

$ ar d [archive.a] [file.o]

ar [-X3264] [-]operation[modifiers] archive [files_...]

ar creates, modifies, and extracts from archives. It's primarily used to create static libraries (.a files) from object files for use with the linker.
Archives contain multiple files with a table of contents for quick access. Unlike tar, ar is optimized for random access to individual members.

r

Insert (replace) files

Create archive

Create/update archive index (ranlib)

Table of contents

Extract files

Delete files

Quick append (no checking)

Verbose output

Update only newer files

Primarily used for static libraries. For general archiving, use tar instead. Archive index (s) is needed for linker to use the library. No compression.

ar dates back to early Unix in the 1970s. It predates tar and was originally a general-purpose archiver before becoming specialized for library creation.

ranlib(1), nm(1), tar(1), ld(1)