Chương này bao phủ khoảng 30 tiện ích cho việc xử lý các tập tin văn bản. Chung, họ là một tập hợp mạnh mẽ của các công cụ để viết các kịch bản shell. Điều quan trọng nhất, và phức tạp nhất, là sắp xếp. Các lệnh fmt, uniq, và wc thường chỉ là công cụ bạn cần trong một đường ống dẫn để đơn giản hóa hoặc tóm tắt các dữ liệu. | JFSifopOpDF3 MegẹaAd SWUnWSteedVefSw - fittpwwwW. sim filaments in it s blue ion tail in this exposure made Monday morning 3 17 97 using inch F 4 Newtonian reflecting telescope. The 15 minute exposure was made on Fujicolor SG-800 Plus film. 8BIM 8BI . Summary This chapter covered about 30 utilities for processing text files. Collectively they are a powerful set of tools for writing shell scripts. The most important and most complex is sort. The fmt uniq and wc commands are often just the tools you need in a pipeline to simplify or summarize data. When you need to get a quick overview of a collection of unfamiliar files file head strings and tail are often a better choice than visiting each file in turn with a text editor. a2ps tgrind and vgrind can make listings of your programs including shell scripts easier to read. 89 Simpo PDF Merge and Split Unregistered Version - http Chapter 5. Pipelines Can Do Amazing Things In this chapter we solve several relatively simple text processing jobs. What s interesting about all the examples here is that they are scripts built from simple pipelines chains of one command hooked into another. Yet each one accomplishes a significant task. When you tackle a text processing problem in Unix it is important to keep the Unix tool philosophy in mind ask yourself how the problem can be broken down into simpler jobs for each of which there is already an existing tool or for which you can readily supply one with a few lines of a shell program or with a scripting language. . Extracting Data from Structured Text Files Most administrative files in Unix are simple flat text files that you can edit print and read without any special file-specific tools. Many of them reside in the standard directory etc. Common examples are the password and group files passwd and group the filesystem mount table fstab or vfstab the hosts file hosts the default shell startup file profile and the system startup and shutdown .
