Transcript ar: Unix Archiver “UNIX for Programmers and Users” Email:

ar: Unix Archiver
Lecturer: Prof. Andrzej (AJ) Bieszczad
Email: [email protected]
Phone: 818-677-4954
“UNIX for Programmers and Users”
Third Edition, Prentice-Hall, GRAHAM GLASS, KING ABLES
Slides partially adapted from Kumoh National University of Technology (Korea) and NYU
ar: Unix Archiver
 THE UNIX ARCHIVE SYSTEM: AR
- When a set of object modules is stored in an archive file,
it may be accessed from the cc compiler and the ld loader
by simply supplying the name of the archive file as an argument.
- Any object modules that are needed from the archive file
are automatically linked as necessary.
- Creating an Archive
An archive is automatically created when the first file is added.
- Adding a File
To add a file to a named archive,
use the ar utility with the “r” option as follows:
ar r archiveName { fileName }+
Prof. Andrzej (AJ) Bieszczad Email: [email protected] Phone: 818-677-4954
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ar: Unix Archiver
Utility: ar key archiveName { fileName }*
ar allows you to create and manipulate archives.
 “d”, deletes a file from an archive
 “q”, which appends a file onto the end of an archive,
even if it’s already present
 “r”, which adds a file to an archive if it isn’t already there, or
replaces the current version if it is
 “t”, which displays an archive’s table of contents
to standard output
 “x”, which copies a list of files from an archive into the current
directory
 “v”, which generates verbose output
Prof. Andrzej (AJ) Bieszczad Email: [email protected] Phone: 818-677-4954
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ar: Unix Archiver
 THE UNIX ARCHIVE SYSTEM: AR
- Appending a File
ar q archiveName { fileName }+
appends all of the specified files to the archive file archiveName,
regardless of whether they already exist.
- Obtaining a Table of Contents
To obtain a table of contents of an archive,
ar t archiveName
Prof. Andrzej (AJ) Bieszczad Email: [email protected] Phone: 818-677-4954
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ar: Unix Archiver
 THE UNIX ARCHIVE SYSTEM: AR
- Deleting a File
To delete a list of files from an archive,
ar d archiveName { fileName }+
- Extracting a File
To copy a list of files from an archive to the current directory,
ar x archiveName { fileName }+
Prof. Andrzej (AJ) Bieszczad Email: [email protected] Phone: 818-677-4954
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ar: Unix Archiver
 Maintaining an Archive from the Command Line
- an example that illustrates how an archive may be built and
manipulated from the command line.
$ cc -c reverse.c palindrome.c main2.c ---> creates object modules.
$ ls *.o
main2.o palindrome.o reverse.o
$ ar r string.a reverse.o palindrome.o ---> add them to an archive
ar: creating string.a
$ ar t string.a
reverse.o
palindrome.o
$ cc main2.o string.a -o main2
---> obtain a table of contents.
$ main2
palindrome(“cat”)=0
palindrome(“noon”)=1
---> execute the program.
---> link the object modules.
Prof. Andrzej (AJ) Bieszczad Email: [email protected] Phone: 818-677-4954
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ar: Unix Archiver
 Maintaining an Archive from the Command Line
$ ar d string.a reverse.o
---> delete a module.
$ ar t string.a
---> confirm deletion.
palindrome.o
$ ar r string.a reverse.o
---> put it back again.
$ ar t string.a
---> confirm addition.
palindrome.o
reverse.o
$ rm palindrome.o reverse.o
---> delete originals.
$ ls *.o
---> confirm
main2.o
$ ar x string.a palindrome.o reverse.o ---> copy them back again.
$ ls *.o
---> confirm
main2.o palindrome.o reverse.o
$_
Prof. Andrzej (AJ) Bieszczad Email: [email protected] Phone: 818-677-4954
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ar: Unix Archiver
 Maintaining an Archive Using make
- To refer to an object file inside an archive,
place the name of the object file inside parentheses,
preceded by the name of the archive.
- updated “main2.make” file that uses archives instead of plain object
files:
main2: main2.o string.a(reverse.o) string.a(palindrome.o)
cc main2.o string.a -o main2
main2.o: palindrome.h
string.a(reverse.o): reverse.h
string.a(palindrome.o): palindrome.h reverse.h
Prof. Andrzej (AJ) Bieszczad Email: [email protected] Phone: 818-677-4954
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ar: Unix Archiver
 Maintaining an Archive Using make
- the output from a make performed using this file:
$ rm *.o
$ make -f main2.make
cc -c main2.c
cc -c reverse.c
ar rv string.a reverse.o
a - reverse.o
ar: creating string.a
rm -f reverse.o
cc -c palindrome.c
ar rv string.a palindrome.o
a - palindrome.o
rm -f palindrome.o
cc main2.o string.a -o main2
$_
---> remove all object modules.
---> perform a make.
---> object modules is automatically saved.
---> original is removed automatically
--->archived object modules are accessed.
Prof. Andrzej (AJ) Bieszczad Email: [email protected] Phone: 818-677-4954
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ar: Unix Archiver
 Ordering Archives
- if an object module A contains a function that calls a function in
an object module B,
then B must come before A in the link sequence.
- If A and B are in the same library,
then B must appear before A in the library.
- Creating a Table of Contents: ranlib
On older systems where this ordering is a problem,
you can help the linker to resolve out-of-order object modules
by adding a table of contents to each archive
by using the ranlib utility.
Prof. Andrzej (AJ) Bieszczad Email: [email protected] Phone: 818-677-4954
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ar: Unix Archiver
 Ordering Archives
Utility : ranlib { archive }+
ranlib adds a table of contents to each specified archive.
It does so by inserting an entry called “_.SYMDEF” into the archive.
- the unresolved reference error
due to an out-of-order sequence of object modules
in the “string.a” archive.
$ ar r string.a reverse.o palindrome.o ---> this order causes problems.
ar: creating string.a
$ cc main2.o string.a -o main2
---> compile fails.
ld: string.a : warning: archive has no table of contents; add one using
ranlib(1)
ld: Undefined symbol
_reverse
$ ranlib string.a
---> add a table of contents.
Prof. Andrzej (AJ) Bieszczad Email: [email protected] Phone: 818-677-4954
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ar: Unix Archiver
 Ordering Archives
$ ranlib string.a
$ cc main2.o string.a -o main2
$ main2
palindrome (“cat”) = 0
palindrome (“noon”) = 1
$_
---> add a table of contents.
---> no problem now.
Prof. Andrzej (AJ) Bieszczad Email: [email protected] Phone: 818-677-4954
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