What is open files in linux. Linux Interview Questions: Open Files / Open File Descriptors – The, of 1024 per process, any new process and worker threads will be blocked. Task: Linux List Open Files For Process. First you need to find out PID of process. Jun 11, 2012 The UNIX Porting Guide is a first stop for UNIX developers coming to OS X. This document helps guide developers in bringing applications written for UNIX-based operating systems to OS X. It provides the background needed to understand the operating system.
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The UNIX Porting Guide is a first stop for UNIX developers coming to OS X. This document helps guide developers in bringing applications written for UNIX-based operating systems to OS X. It provides the background needed to understand the operating system. It touches on some of the design decisions, and it provides a listing and discussion of some of the main areas that you should be concerned with in bringing UNIX applications to OS X. It also points out some of the advanced features of OS X not available in traditional UNIX applications that you can add to your ported applications.
This document also provides an entry point for other documentation on various subjects that may be of interest if you are porting an application from a UNIX environment to OS X.
This document is an overview, not a tutorial. In many regards it is a companion to the more extensive Mac Technology Overview, but with a bias toward the UNIX developer.
This document also does not cover porting shell scripts to OS X. For more information about shell scripts and OS X, you should read Shell Scripting Primer.
Bringing UNIX Apps to OS X
The introduction of UNIX-like operating systems such as FreeBSD and Linux for personal computers was a great step in bringing the power and stability of UNIX to the mass market. Generally though, these projects were driven by power users and developers for their own use, without making design decisions that would make UNIX palatable to consumers. OS X, on the other hand, was designed from the beginning with end users in mind.
With this operating system, Apple builds its well-known strengths in simplicity and elegance of design on a UNIX-based foundation. Rather than reinventing what has already been done well, Apple is combining their strengths with the strengths brought about by many years of advancement by the UNIX community.
Who Should Read This Document?
Any UNIX developers can benefit from reading this book.
- In-house corporate application developers
- Commercial UNIX developers
- Open source developers
- Open source porters
- Higher education faculty, staff, and students
- Science and research developers
If you’re a commercial UNIX developer, you are already familiar with other UNIX-based systems and may want to understand the differences between other systems and OS X. You might be interested in porting the GUI from an X11 environment into a native graphics environment using Carbon or Cocoa. You may also have special needs such as direct hardware access, exclusive file access guarantees, and so on.
If you’re a corporate in-house developer (developing applications for internal use), you probably want to port applications with minimal code divergence.
If you’re an open source developer, you might want information about how to incorporate new technologies into your software, and may be interested in GUI porting, depending on your level of interest. Alternately, you might be interested only in quickly porting code to a new platform with minimal changes so that you can easily get your changes back into the official code base. If so, you may be more likely to use compatibility shims than to use new APIs.
No matter what “flavor” of developer you are, this book will provide information that is helpful to you and provide pointers to additional documents that may be of interest.
Important: If you are primarily interested in shell scripts and command-line compatibility, you should read Designing Scripts for Cross-Platform Deployment in Shell Scripting Primer. That document gives a more thorough overview of the shell environment in OS X, including common cross-platform compatibility issues.
Important: This document is not designed for pure Java developers. OS X has a full and robust Java 2 Platform, Standard Edition (J2SE) implementation. If you have a pure Java application already, it should run in OS X.
Organization of This Document
This document is a first stop for UNIX developers coming to OS X. It contains many links to more extensive documentation. Specific details of implementation are covered here only in cases where it is not adequately covered in other places in the documentation set.
To use this document most effectively, first read Overview of OS X to find out the basics about the Mac and to get some of the high-level information you need to begin your port. If you already have an application that builds on other UNIX-based platforms, Compiling Your Code in OS X will help you find out how to compile your code on OS X.
Most of your effort, however, should be spent towards making decisions concerning which, if any, graphical user interface to implement with your application. Choosing a Graphical Environment for Your Application helps you with this.
If you want to refactor your application to take advantage of the rich feature set of OS X, see Additional Features for examples of features available in OS X.
Once you have a complete application, read Distributing Your Application for information on getting your application to OS X users.
See Also
Os X 10.12
Developer documentation can be found at Apple’s developer website at http://developer.apple.com/. This site contains reference, conceptual, and tutorial material for the many facets of development on OS X. The OS X Developer Tools CD includes a snapshot of the developer documentation, which can be searched for and viewed in Xcode’s doc viewer. The
man
pages are also included with the OS X Developer Tools.Apple Developer Connection (ADC) offers a variety of membership levels to help you in your development. These range from free memberships that give you access to developer software, to paid memberships that provide support incidents as well as the possibility of software seeds. More information on memberships is available at http://developer.apple.com.
Once a year in early Summer, Apple hosts the Worldwide Developers Conference (WWDC) in the San Francisco, California Bay area. This is an extremely valuable resource for developers trying to get an overall picture of OS X as well as specific implementation details of individual technologies. Information on WWDC is available on the ADC website.
Apple hosts an extensive array of public mailing lists. These are available for public subscription and searching at http://lists.apple.com. The unix-porting list is highly recommended. The darwin-dev and darwinos-users lists also offer much help but less specific to the task of porting.
In addition to Apple’s own resources, many external resources exist, for example, O’Reilly’s Mac DevCenter, http://www.oreillynet.com/mac/.
Copyright © 2002, 2012 Apple Inc. All Rights Reserved. Terms of Use | Privacy Policy | Updated: 2012-06-11
OS X is a modern operating system that combines the power and stability of UNIX-based operating systems with the simplicity and elegance of the Macintosh. For years, power users and developers have recognized the strengths of UNIX and its offshoots. While UNIX-based operating systems are indispensable to developers and power users, consumers have rarely been able to enjoy their benefits because of the perceived complexity. Instead consumers have lived with a generation of desktop computers that could only hope to achieve the strengths that UNIX-based operating systems have had from the beginning.
This chapter is for anyone interested in an overview of OS X—its lineage and its open source core, called Darwin. Here you will find background information about OS X and how your application fits in.
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The Family Tree
Although this document covers the basic concepts in bringing UNIX applications to OS X, it is by no means comprehensive. This section is provided to give you a hint on where to look for additional documentation by outlining how OS X came to be. Knowing a little about the lineage of OS X will help you to find more resources as the need arises.
• BSD
Part of the history of OS X goes back to Berkeley Software Distributions (BSD) UNIX of the late seventies and early eighties. Specifically, it is based in part on BSD 4.4 Lite. On a system level, many of the design decisions are made to align with BSD-style UNIX systems. Most libraries and utilities are from FreeBSD (http://www.freebsd.org/), but some are derived from NetBSD (http://www.netbsd.org/). For future development, OS X has adopted FreeBSD as a reference code base for BSD technology. Work is ongoing to more closely synchronize all BSD tools and libraries with the FreeBSD-stable branch..
• Mach
Although OS X must credit BSD for most of the underlying levels of the operating system, OS X also owes a major debt to Mach. The kernel is heavily influenced in its design philosophy by Carnegie Mellon’s Mach project. The kernel is not a pure microkernel implementation, since the address space is shared with the BSD portion of the kernel and the I/O Kit.
• NEXTSTEP
In figuring out what makes OS X tick, it is important to recognize the influences of NEXTSTEP and OPENSTEP in its design. Apple’s acquisition of NeXT in 1997 was a major key in bringing OS X from the drawing board into reality. Many parts of OS X of interest to UNIX developers are enhancements and offshoots of the technology present in NEXTSTEP. From the file system layer to the executable format and from the high-level Cocoa API to the kernel itself, the lineage of OS X as a descendant of NEXTSTEP is evident.
• Earlier Version of the Mac OS
Although it shares its name with earlier versions of the Mac OS, OS X is a fundamentally new operating system. This does not mean that all that went before has been left out. OS X still includes many of the features that Mac OS 9 and earlier versions included. Although your initial port to OS X may not use any of the features inherited from Mac OS 9, as you enhance the application, you might take advantage of some of the features provided by technologies like ColorSync or the Carbon APIs. Mac OS 9 is also the source of much of the terminology used in OS X.
OS X and Darwin
The word Darwin is often used to refer to the underpinnings of OS X. In fact, in some circles OS X itself is rarely mentioned at all. It is important to understand the distinction between the two—how they are related and how they differ.
Darwin is the core of the OS X operating system. Although Darwin can stand alone as an independent operating system, it includes only a subset of the features available in OS X. Figure 1-1 shows how Darwin is related to OS X as a whole.
Darwin is an open source project. With it, you as a developer gain access to the foundation of OS X. Its openness also allows you to submit changes that you think should be reflected in OS X as a whole. Darwin has been released as a separate project that runs on PowerPC-based Macintosh computers as well as x86-compatible computers. Although it could be considered a standalone operating system in its own right, many of the fundamental design decisions of Darwin are governed by its being embedded within OS X. In bringing your applications to the platform, you should target OS X version 10.1.4 (Darwin 5.4) or later.
OS X itself is not an Open Source project. As you can see from Figure 1-1, there are many parts of OS X that are not included in the Open Source Darwin components. Part of your job while porting is deciding where your application will fit in OS X.
If you are a developer whose tool is a command-line tool (or has a useful subset that is a command-line tool), you can, of course, simply port your application as a command-line tool or service, which is usually not that complicated. By doing this you gain a small benefit, in that it is now available to OS X users who are familiar with the UNIX command-line environment. You will not be able to market it to OS X users as a whole though, since many users do not even know how to access the command line on their computers.
The basic steps in porting a UNIX application to OS X typically include:
- Port to the command line.
- Provide a graphical user interface (GUI).
What Macintosh Users Expect
In bringing your UNIX application to OS X, you are entering a world where great emphasis is placed on user interactions. This brings you many opportunities and benefits as a developer, but also some responsibilities.
Benefits of Porting to OS X
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Porting to OS X has three primary benefits:
- stable long-term customer base
- good inroad into education
- powerful developer tools
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Bringing UNIX applications to OS X can be very profitable if done correctly. Well-designed Macintosh applications of years past are the standards of today. PhotoShop, Illustrator, and Excel are all applications that first made their name on the Macintosh. Now is the time to win the hearts of Macintosh users with the next great application. In a word, possibly millions of paying customers!
Macintosh users are willing to spend their money on great applications because they know that Apple strives to give them a high-quality user environment. Apple developers are known for providing great applications for that environment.
For years, Apple has been known for its commitment to education. OS X targets the education market for developers and is an ideal platform for learning for students. With its standards-based technologies as well as home-grown technologies, you have an ideal platform for use in educational application deployment and development.
OS X also provides benefits in a development environment. Apple strives for standards first, then it adds that little bit that makes it better on a Mac. As a developer, you have access to many of the development tools and environments that you have on other platforms, like Java, OpenGL, POSIX libraries, and the BSD TCP/IP stack, but you also have built-in benefits like the Apache Web server on every computer, the Cocoa object-oriented development environment, a PDF-based display system (Quartz), Kerberos, QuickTime, a dynamic core audio implementation, and a suite of world-class developer tools. By adding a native OS X front end to your application, you can achieve a cost-effective new deployment platform with minimal additional development effort.
OS X adds tremendous value both to you and your customers on a standards-based operating system.
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Responsibilities of Porting to OS X
Along with benefits come responsibilities. If you have decided to make a full-featured Mac app, here are some guidelines to keep in mind.
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- An OS X user should never have to resort to the command line to perform any task in an application with a graphical user interface. This is especially important to remember since the BSD user environment may not even be installed on a user’s system. The libraries and kernel environment are of course there by default, but the tools may not be.
- If you are making graphical design decisions, you need to become familiar with the OS X Human Interface Guidelines, available from the Apple developer website. These are the standards that Macintosh users expect their applications to live up to. Well-behaved applications from Apple and third-party developers give the Macintosh its reputation as the most usable interface on the planet.
The responsibilities boil down to striving for an excellent product from a user’s perspective. OS X gives you the tools to make your applications shine.
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Copyright © 2002, 2012 Apple Inc. All Rights Reserved. Terms of Use | Privacy Policy | Updated: 2012-06-11