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The shell's job, then, is to translate the user's command lines into operating system instructions. For example, consider this command line: sort -n phonelist > phonelist.sorted This means, "Sort lines in the file phonelist in numerical order, and put the result in the file phonelist.sorted." Here's what the shell does with this command:
Of course, each of these steps really involves several substeps, each of which includes a particular instruction to the underlying operating system. Remember that the shell itself is not UNIX just the user interface to it. UNIX is one of the first operating systems to make the user interface independent of the operating system. |
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