Unix sockets allow inter-process communication IPC between processes on the same machine.
A shell is an environment which allows commands to be issued, and also includes facilities to control input and output, and programming facilities to allow complex sets of actions to be performed.
Whenever you type commands at the prompt in Unix, you are actually communicating interactively with a shell. In addition to typing commands directly to the shell, you can place them in a file which must be given execute permissionand then run the file. A file containing UNIX shell commands is known as a script or shell script.
Executing the script is equivalent to typing the commands within it. The Unix shells are actually quite sophisticated programming languages in their own right: Together with the large number of special utility programs which are provided as standard, scripts make Unix an extremely powerful operating system.
Scripts are interpreted rather than compiled, which means that the computer must translate them each time it runs them: However, they are extremely good where you want to use Operating System facilities; for example, when processing files in some fashion.
There are actually no less than three different types of scripts supported in Unix: Bourne shell, C shell, and Korn shell. Bourne is the most common, Korn the most powerful, and C the most C-like handy for C programmers.
This tutorial will concentrate on the simplest of the three: A simple Bourne-shell script If you simply type Unix commands into a file, and make it executable, then run it, Unix will assume that the commands in it are written in whatever shell language you happen to be using at the time in your case, this is probably the C shell.
To make sure that the correct shell is run, the first line of the script should always indicate which one is required. Below is illustrated a simple Bourne-shell script: Save the file, calling it hello. Then make the hello file executable by typing: Naming Shell Script Files You can give your shell scripts almost any name you like.
If the name you use happens to already be an existing UNIX command, when you try to run your script you will end up running the system-defined command instead.
Some fairly obvious names can cause you this problem; for example, test. To make sure that your intended name is O. For example, to find out whether there are commands called dc and dac, type:Accessing the Public Data API with Unix Command Line: On This Page: API Version Unix Command Line Sample Code.
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