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Red Hat Linux unleashed Second Edition phần 8

người đàn ông. Khi một người đàn ông trang được truy cập, chương trình định dạng người đàn ông đó tiết kiệm một trang bản sao của các trang người đàn ông định dạng trong NPAC (/ etc / NPAC) thư mục. | Automation Programming and Modifying Source Code 472 Part VI 2. The compiler parses the modified code for correct syntax. This builds a symbol table and creates an intermediate object format. Most symbols have specific memory addresses assigned although symbols defined in other modules such as external variables do not. 3. The last compilation stage linking ties together different files and libraries and links the files by resolving the symbols that hadn t previously been resolved. Executing the Program The output from this program appears in Listing 23.8. Listing 23.8. Output from the sample.c program. sample 1. 1 1 1.00000 2. 4 8 1.41421 3. 9 27 1.73205 4. 16 64 2.00000 5. 25 125 2.23607 6. 36 216 2.44949 7. 49 343 2.64575 8. 64 512 2.82843 9. 81 729 3.00000 10. 100 1000 3.16228 NOTE To execute a program just type its name at a shell prompt. The output will immediately follow. Building Large Applications C programs can be broken into any number of files as long as no single function spans more than one file. To compile this program you compile each source file into an intermediate object before you link all the objects into a single executable. The -c flag tells the compiler to stop at this stage. During the link stage all the object files should be listed on the command line. Object files are identified by the .0 suffix. Making Libraries with ar If several different programs use the same functions they can be combined in a single library archive. The ar command is used to build a library. When this library is included on the compile line the archive is searched to resolve any external symbols. Listing 23.9 shows an example of building and using a library. C and C Programming 473 Chapter 23 Listing 23.9. Building a large application. gcc -c sine.c gcc -c cosine.c gcc -c tangent.c ar c libtrig.a sine.o cosine.o tangent.o gcc -c mainprog.c gcc -o mainprog mainprog.o libtrig.a Large applications can require hundreds of source code files. Compiling and linking these